FreeType » Docs » Core API » Base Interface
Base Interface¶
Synopsis¶
This section describes the most important public high-level API functions of FreeType 2.
FT_Library¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_LibraryRec_ *FT_Library;
A handle to a FreeType library instance. Each ‘library’ is completely independent from the others; it is the ‘root’ of a set of objects like fonts, faces, sizes, etc.
It also embeds a memory manager (see FT_Memory), as well as a scan-line converter object (see FT_Raster).
[Since 2.5.6] In multi-threaded applications it is easiest to use one FT_Library object per thread. In case this is too cumbersome, a single FT_Library object across threads is possible also, as long as a mutex lock is used around FT_New_Face and FT_Done_Face.
note
Library objects are normally created by FT_Init_FreeType, and destroyed with FT_Done_FreeType. If you need reference-counting (cf. FT_Reference_Library), use FT_New_Library and FT_Done_Library.
FT_Face¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_FaceRec_* FT_Face;
A handle to a typographic face object. A face object models a given typeface, in a given style.
note
A face object also owns a single FT_GlyphSlot object, as well as one or more FT_Size objects.
Use FT_New_Face or FT_Open_Face to create a new face object from a given filepath or a custom input stream.
Use FT_Done_Face to destroy it (along with its slot and sizes).
An FT_Face object can only be safely used from one thread at a time. Similarly, creation and destruction of FT_Face with the same FT_Library object can only be done from one thread at a time. On the other hand, functions like FT_Load_Glyph and its siblings are thread-safe and do not need the lock to be held as long as the same FT_Face object is not used from multiple threads at the same time.
also
See FT_FaceRec for the publicly accessible fields of a given face object.
FT_Size¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_SizeRec_* FT_Size;
A handle to an object that models a face scaled to a given character size.
note
An FT_Face has one active FT_Size object that is used by functions like FT_Load_Glyph to determine the scaling transformation that in turn is used to load and hint glyphs and metrics.
You can use FT_Set_Char_Size, FT_Set_Pixel_Sizes, FT_Request_Size or even FT_Select_Size to change the content (i.e., the scaling values) of the active FT_Size.
You can use FT_New_Size to create additional size objects for a given FT_Face, but they won't be used by other functions until you activate it through FT_Activate_Size. Only one size can be activated at any given time per face.
also
See FT_SizeRec for the publicly accessible fields of a given size object.
FT_GlyphSlot¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_GlyphSlotRec_* FT_GlyphSlot;
A handle to a given ‘glyph slot’. A slot is a container that can hold any of the glyphs contained in its parent face.
In other words, each time you call FT_Load_Glyph or FT_Load_Char, the slot's content is erased by the new glyph data, i.e., the glyph's metrics, its image (bitmap or outline), and other control information.
also
See FT_GlyphSlotRec for the publicly accessible glyph fields.
FT_CharMap¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_CharMapRec_* FT_CharMap;
A handle to a character map (usually abbreviated to ‘charmap’). A charmap is used to translate character codes in a given encoding into glyph indexes for its parent's face. Some font formats may provide several charmaps per font.
Each face object owns zero or more charmaps, but only one of them can be ‘active’, providing the data used by FT_Get_Char_Index or FT_Load_Char.
The list of available charmaps in a face is available through the face->num_charmaps and face->charmaps fields of FT_FaceRec.
The currently active charmap is available as face->charmap. You should call FT_Set_Charmap to change it.
note
When a new face is created (either through FT_New_Face or FT_Open_Face), the library looks for a Unicode charmap within the list and automatically activates it. If there is no Unicode charmap, FreeType doesn't set an ‘active’ charmap.
also
See FT_CharMapRec for the publicly accessible fields of a given character map.
FT_Encoding¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef enum FT_Encoding_
{
FT_ENC_TAG( FT_ENCODING_NONE, 0, 0, 0, 0 ),
FT_ENC_TAG( FT_ENCODING_MS_SYMBOL, 's', 'y', 'm', 'b' ),
FT_ENC_TAG( FT_ENCODING_UNICODE, 'u', 'n', 'i', 'c' ),
FT_ENC_TAG( FT_ENCODING_SJIS, 's', 'j', 'i', 's' ),
FT_ENC_TAG( FT_ENCODING_PRC, 'g', 'b', ' ', ' ' ),
FT_ENC_TAG( FT_ENCODING_BIG5, 'b', 'i', 'g', '5' ),
FT_ENC_TAG( FT_ENCODING_WANSUNG, 'w', 'a', 'n', 's' ),
FT_ENC_TAG( FT_ENCODING_JOHAB, 'j', 'o', 'h', 'a' ),
/* for backward compatibility */
FT_ENCODING_GB2312 = FT_ENCODING_PRC,
FT_ENCODING_MS_SJIS = FT_ENCODING_SJIS,
FT_ENCODING_MS_GB2312 = FT_ENCODING_PRC,
FT_ENCODING_MS_BIG5 = FT_ENCODING_BIG5,
FT_ENCODING_MS_WANSUNG = FT_ENCODING_WANSUNG,
FT_ENCODING_MS_JOHAB = FT_ENCODING_JOHAB,
FT_ENC_TAG( FT_ENCODING_ADOBE_STANDARD, 'A', 'D', 'O', 'B' ),
FT_ENC_TAG( FT_ENCODING_ADOBE_EXPERT, 'A', 'D', 'B', 'E' ),
FT_ENC_TAG( FT_ENCODING_ADOBE_CUSTOM, 'A', 'D', 'B', 'C' ),
FT_ENC_TAG( FT_ENCODING_ADOBE_LATIN_1, 'l', 'a', 't', '1' ),
FT_ENC_TAG( FT_ENCODING_OLD_LATIN_2, 'l', 'a', 't', '2' ),
FT_ENC_TAG( FT_ENCODING_APPLE_ROMAN, 'a', 'r', 'm', 'n' )
} FT_Encoding;
/* these constants are deprecated; use the corresponding `FT_Encoding` */
/* values instead */
#define ft_encoding_none FT_ENCODING_NONE
#define ft_encoding_unicode FT_ENCODING_UNICODE
#define ft_encoding_symbol FT_ENCODING_MS_SYMBOL
#define ft_encoding_latin_1 FT_ENCODING_ADOBE_LATIN_1
#define ft_encoding_latin_2 FT_ENCODING_OLD_LATIN_2
#define ft_encoding_sjis FT_ENCODING_SJIS
#define ft_encoding_gb2312 FT_ENCODING_PRC
#define ft_encoding_big5 FT_ENCODING_BIG5
#define ft_encoding_wansung FT_ENCODING_WANSUNG
#define ft_encoding_johab FT_ENCODING_JOHAB
#define ft_encoding_adobe_standard FT_ENCODING_ADOBE_STANDARD
#define ft_encoding_adobe_expert FT_ENCODING_ADOBE_EXPERT
#define ft_encoding_adobe_custom FT_ENCODING_ADOBE_CUSTOM
#define ft_encoding_apple_roman FT_ENCODING_APPLE_ROMAN
An enumeration to specify character sets supported by charmaps. Used in the FT_Select_Charmap API function.
note
Despite the name, this enumeration lists specific character repertories (i.e., charsets), and not text encoding methods (e.g., UTF-8, UTF-16, etc.).
Other encodings might be defined in the future.
values
| FT_ENCODING_NONE |
The encoding value 0 is reserved for all formats except BDF, PCF, and Windows FNT; see below for more information. |
| FT_ENCODING_UNICODE |
The Unicode character set. This value covers all versions of the Unicode repertoire, including ASCII and Latin-1. Most fonts include a Unicode charmap, but not all of them. For example, if you want to access Unicode value U+1F028 (and the font contains it), use value 0x1F028 as the input value for |
| FT_ENCODING_MS_SYMBOL |
Microsoft Symbol encoding, used to encode mathematical symbols and wingdings. For more information, see ‘https://www.microsoft.com/typography/otspec/recom.htm#non-standard-symbol-fonts’, ‘http://www.kostis.net/charsets/symbol.htm’, and ‘http://www.kostis.net/charsets/wingding.htm’. This encoding uses character codes from the PUA (Private Unicode Area) in the range U+F020-U+F0FF. |
| FT_ENCODING_SJIS |
Shift JIS encoding for Japanese. More info at ‘https://en.wikipedia.org/wiki/Shift_JIS’. See note on multi-byte encodings below. |
| FT_ENCODING_PRC |
Corresponds to encoding systems mainly for Simplified Chinese as used in People's Republic of China (PRC). The encoding layout is based on GB 2312 and its supersets GBK and GB 18030. |
| FT_ENCODING_BIG5 |
Corresponds to an encoding system for Traditional Chinese as used in Taiwan and Hong Kong. |
| FT_ENCODING_WANSUNG |
Corresponds to the Korean encoding system known as Extended Wansung (MS Windows code page 949). For more information see ‘https://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WindowsBestFit/bestfit949.txt’. |
| FT_ENCODING_JOHAB |
The Korean standard character set (KS C 5601-1992), which corresponds to MS Windows code page 1361. This character set includes all possible Hangul character combinations. |
| FT_ENCODING_ADOBE_LATIN_1 |
Corresponds to a Latin-1 encoding as defined in a Type 1 PostScript font. It is limited to 256 character codes. |
| FT_ENCODING_ADOBE_STANDARD |
Adobe Standard encoding, as found in Type 1, CFF, and OpenType/CFF fonts. It is limited to 256 character codes. |
| FT_ENCODING_ADOBE_EXPERT |
Adobe Expert encoding, as found in Type 1, CFF, and OpenType/CFF fonts. It is limited to 256 character codes. |
| FT_ENCODING_ADOBE_CUSTOM |
Corresponds to a custom encoding, as found in Type 1, CFF, and OpenType/CFF fonts. It is limited to 256 character codes. |
| FT_ENCODING_APPLE_ROMAN |
Apple roman encoding. Many TrueType and OpenType fonts contain a charmap for this 8-bit encoding, since older versions of Mac OS are able to use it. |
| FT_ENCODING_OLD_LATIN_2 |
This value is deprecated and was neither used nor reported by FreeType. Don't use or test for it. |
| FT_ENCODING_MS_SJIS |
Same as FT_ENCODING_SJIS. Deprecated. |
| FT_ENCODING_MS_GB2312 |
Same as FT_ENCODING_PRC. Deprecated. |
| FT_ENCODING_MS_BIG5 |
Same as FT_ENCODING_BIG5. Deprecated. |
| FT_ENCODING_MS_WANSUNG |
Same as FT_ENCODING_WANSUNG. Deprecated. |
| FT_ENCODING_MS_JOHAB |
Same as FT_ENCODING_JOHAB. Deprecated. |
note
By default, FreeType enables a Unicode charmap and tags it with FT_ENCODING_UNICODE when it is either provided or can be generated from PostScript glyph name dictionaries in the font file. All other encodings are considered legacy and tagged only if explicitly defined in the font file. Otherwise, FT_ENCODING_NONE is used.
FT_ENCODING_NONE is set by the BDF and PCF drivers if the charmap is neither Unicode nor ISO-8859-1 (otherwise it is set to FT_ENCODING_UNICODE). Use FT_Get_BDF_Charset_ID to find out which encoding is really present. If, for example, the cs_registry field is ‘KOI8’ and the cs_encoding field is ‘R’, the font is encoded in KOI8-R.
FT_ENCODING_NONE is always set (with a single exception) by the winfonts driver. Use FT_Get_WinFNT_Header and examine the charset field of the FT_WinFNT_HeaderRec structure to find out which encoding is really present. For example, FT_WinFNT_ID_CP1251 (204) means Windows code page 1251 (for Russian).
FT_ENCODING_NONE is set if platform_id is TT_PLATFORM_MACINTOSH and encoding_id is not TT_MAC_ID_ROMAN (otherwise it is set to FT_ENCODING_APPLE_ROMAN).
If platform_id is TT_PLATFORM_MACINTOSH, use the function FT_Get_CMap_Language_ID to query the Mac language ID that may be needed to be able to distinguish Apple encoding variants. See
https://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/Readme.txt
to get an idea how to do that. Basically, if the language ID is 0, don't use it, otherwise subtract 1 from the language ID. Then examine encoding_id. If, for example, encoding_id is TT_MAC_ID_ROMAN and the language ID (minus 1) is TT_MAC_LANGID_GREEK, it is the Greek encoding, not Roman. TT_MAC_ID_ARABIC with TT_MAC_LANGID_FARSI means the Farsi variant the Arabic encoding.
FT_ENC_TAG¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#ifndef FT_ENC_TAG
#define FT_ENC_TAG( value, a, b, c, d ) \
value = ( ( (FT_UInt32)(a) << 24 ) | \
( (FT_UInt32)(b) << 16 ) | \
( (FT_UInt32)(c) << 8 ) | \
(FT_UInt32)(d) )
#endif /* FT_ENC_TAG */
This macro converts four-letter tags into an unsigned long. It is used to define ‘encoding’ identifiers (see FT_Encoding).
note
Since many 16-bit compilers don't like 32-bit enumerations, you should redefine this macro in case of problems to something like this:
#define FT_ENC_TAG( value, a, b, c, d ) value
to get a simple enumeration without assigning special numbers.
FT_FaceRec¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_FaceRec_
{
FT_Long num_faces;
FT_Long face_index;
FT_Long face_flags;
FT_Long style_flags;
FT_Long num_glyphs;
FT_String* family_name;
FT_String* style_name;
FT_Int num_fixed_sizes;
FT_Bitmap_Size* available_sizes;
FT_Int num_charmaps;
FT_CharMap* charmaps;
FT_Generic generic;
/*# The following member variables (down to `underline_thickness`) */
/*# are only relevant to scalable outlines; cf. @FT_Bitmap_Size */
/*# for bitmap fonts. */
FT_BBox bbox;
FT_UShort units_per_EM;
FT_Short ascender;
FT_Short descender;
FT_Short height;
FT_Short max_advance_width;
FT_Short max_advance_height;
FT_Short underline_position;
FT_Short underline_thickness;
FT_GlyphSlot glyph;
FT_Size size;
FT_CharMap charmap;
/*@private begin */
FT_Driver driver;
FT_Memory memory;
FT_Stream stream;
FT_ListRec sizes_list;
FT_Generic autohint; /* face-specific auto-hinter data */
void* extensions; /* unused */
FT_Face_Internal internal;
/*@private end */
} FT_FaceRec;
FreeType root face class structure. A face object models a typeface in a font file.
fields
| num_faces |
The number of faces in the font file. Some font formats can have multiple faces in a single font file. |
| face_index |
This field holds two different values. Bits 0-15 are the index of the face in the font file (starting with value 0). They are set to 0 if there is only one face in the font file. [Since 2.6.1] Bits 16-30 are relevant to GX and OpenType variation fonts only, holding the named instance index for the current face index (starting with value 1; value 0 indicates font access without a named instance). For non-variation fonts, bits 16-30 are ignored. If we have the third named instance of face 4, say, Bit 31 is always zero (this is, [Since 2.9] Changing the design coordinates with |
| face_flags |
A set of bit flags that give important information about the face; see |
| style_flags |
The lower 16 bits contain a set of bit flags indicating the style of the face; see [Since 2.6.1] Bits 16-30 hold the number of named instances available for the current face if we have a GX or OpenType variation (sub)font. Bit 31 is always zero (this is, |
| num_glyphs |
The number of glyphs in the face. If the face is scalable and has sbits (see For CID-keyed fonts (not in an SFNT wrapper) this value gives the highest CID used in the font. |
| family_name |
The face's family name. This is an ASCII string, usually in English, that describes the typeface's family (like ‘Times New Roman’, ‘Bodoni’, ‘Garamond’, etc). This is a least common denominator used to list fonts. Some formats (TrueType & OpenType) provide localized and Unicode versions of this string. Applications should use the format-specific interface to access them. Can be In case the font doesn't provide a specific family name entry, FreeType tries to synthesize one, deriving it from other name entries. |
| style_name |
The face's style name. This is an ASCII string, usually in English, that describes the typeface's style (like ‘Italic’, ‘Bold’, ‘Condensed’, etc). Not all font formats provide a style name, so this field is optional, and can be set to |
| num_fixed_sizes |
The number of bitmap strikes in the face. Even if the face is scalable, there might still be bitmap strikes, which are called ‘sbits’ in that case. |
| available_sizes |
An array of Note that FreeType tries to sanitize the strike data since they are sometimes sloppy or incorrect, but this can easily fail. |
| num_charmaps |
The number of charmaps in the face. |
| charmaps |
An array of the charmaps of the face. |
| generic |
A field reserved for client uses. See the |
| bbox |
The font bounding box. Coordinates are expressed in font units (see Note that the bounding box might be off by (at least) one pixel for hinted fonts. See Note that the bounding box does not vary in OpenType variable fonts and should only be used in relation to the default instance. |
| units_per_EM |
The number of font units per EM square for this face. This is typically 2048 for TrueType fonts, and 1000 for Type 1 fonts. Only relevant for scalable formats. |
| ascender |
The typographic ascender of the face, expressed in font units. For font formats not having this information, it is set to |
| descender |
The typographic descender of the face, expressed in font units. For font formats not having this information, it is set to |
| height |
This value is the vertical distance between two consecutive baselines, expressed in font units. It is always positive. Only relevant for scalable formats. If you want the global glyph height, use |
| max_advance_width |
The maximum advance width, in font units, for all glyphs in this face. This can be used to make word wrapping computations faster. Only relevant for scalable formats. |
| max_advance_height |
The maximum advance height, in font units, for all glyphs in this face. This is only relevant for vertical layouts, and is set to |
| underline_position |
The position, in font units, of the underline line for this face. It is the center of the underlining stem. Only relevant for scalable formats. |
| underline_thickness |
The thickness, in font units, of the underline for this face. Only relevant for scalable formats. |
| glyph |
The face's associated glyph slot(s). |
| size |
The current active size for this face. |
| charmap |
The current active charmap for this face. |
note
Fields may be changed after a call to FT_Attach_File or FT_Attach_Stream.
For an OpenType variation font, the values of the following fields can change after a call to FT_Set_Var_Design_Coordinates (and friends) if the font contains an ‘MVAR’ table: ascender, descender, height, underline_position, and underline_thickness.
Especially for TrueType fonts see also the documentation for FT_Size_Metrics.
FT_HAS_HORIZONTAL¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_HORIZONTAL( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_HORIZONTAL ) )
A macro that returns true whenever a face object contains horizontal metrics (this is true for all font formats though).
also
FT_HAS_VERTICAL can be used to check for vertical metrics.
FT_HAS_VERTICAL¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_VERTICAL( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_VERTICAL ) )
A macro that returns true whenever a face object contains real vertical metrics (and not only synthesized ones).
FT_HAS_KERNING¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_KERNING( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_KERNING ) )
A macro that returns true whenever a face object contains kerning data that can be accessed with FT_Get_Kerning.
FT_HAS_FIXED_SIZES¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_FIXED_SIZES( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_FIXED_SIZES ) )
A macro that returns true whenever a face object contains some embedded bitmaps. See the available_sizes field of the FT_FaceRec structure.
FT_HAS_GLYPH_NAMES¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_GLYPH_NAMES( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_GLYPH_NAMES ) )
A macro that returns true whenever a face object contains some glyph names that can be accessed through FT_Get_Glyph_Name.
FT_HAS_COLOR¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_COLOR( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_COLOR ) )
A macro that returns true whenever a face object contains tables for color glyphs.
since
2.5.1
FT_HAS_MULTIPLE_MASTERS¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_MULTIPLE_MASTERS( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS ) )
A macro that returns true whenever a face object contains some multiple masters. The functions provided by FT_MULTIPLE_MASTERS_H are then available to choose the exact design you want.
FT_IS_SFNT¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_IS_SFNT( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_SFNT ) )
A macro that returns true whenever a face object contains a font whose format is based on the SFNT storage scheme. This usually means: TrueType fonts, OpenType fonts, as well as SFNT-based embedded bitmap fonts.
If this macro is true, all functions defined in FT_SFNT_NAMES_H and FT_TRUETYPE_TABLES_H are available.
FT_IS_SCALABLE¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_IS_SCALABLE( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_SCALABLE ) )
A macro that returns true whenever a face object contains a scalable font face (true for TrueType, Type 1, Type 42, CID, OpenType/CFF, and PFR font formats).
FT_IS_FIXED_WIDTH¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_IS_FIXED_WIDTH( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_FIXED_WIDTH ) )
A macro that returns true whenever a face object contains a font face that contains fixed-width (or ‘monospace’, ‘fixed-pitch’, etc.) glyphs.
FT_IS_CID_KEYED¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_IS_CID_KEYED( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_CID_KEYED ) )
A macro that returns true whenever a face object contains a CID-keyed font. See the discussion of FT_FACE_FLAG_CID_KEYED for more details.
If this macro is true, all functions defined in FT_CID_H are available.
FT_IS_TRICKY¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_IS_TRICKY( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_TRICKY ) )
A macro that returns true whenever a face represents a ‘tricky’ font. See the discussion of FT_FACE_FLAG_TRICKY for more details.
FT_IS_NAMED_INSTANCE¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_IS_NAMED_INSTANCE( face ) \
( !!( (face)->face_index & 0x7FFF0000L ) )
A macro that returns true whenever a face object is a named instance of a GX or OpenType variation font.
[Since 2.9] Changing the design coordinates with FT_Set_Var_Design_Coordinates or FT_Set_Var_Blend_Coordinates does not influence the return value of this macro (only FT_Set_Named_Instance does that).
since
2.7
FT_IS_VARIATION¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_IS_VARIATION( face ) \
( !!( (face)->face_flags & FT_FACE_FLAG_VARIATION ) )
A macro that returns true whenever a face object has been altered by FT_Set_MM_Design_Coordinates, FT_Set_Var_Design_Coordinates, or FT_Set_Var_Blend_Coordinates.
since
2.9
FT_SizeRec¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_SizeRec_
{
FT_Face face; /* parent face object */
FT_Generic generic; /* generic pointer for client uses */
FT_Size_Metrics metrics; /* size metrics */
FT_Size_Internal internal;
} FT_SizeRec;
FreeType root size class structure. A size object models a face object at a given size.
fields
| face |
Handle to the parent face object. |
| generic |
A typeless pointer, unused by the FreeType library or any of its drivers. It can be used by client applications to link their own data to each size object. |
| metrics |
Metrics for this size object. This field is read-only. |
FT_Size_Metrics¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Size_Metrics_
{
FT_UShort x_ppem; /* horizontal pixels per EM */
FT_UShort y_ppem; /* vertical pixels per EM */
FT_Fixed x_scale; /* scaling values used to convert font */
FT_Fixed y_scale; /* units to 26.6 fractional pixels */
FT_Pos ascender; /* ascender in 26.6 frac. pixels */
FT_Pos descender; /* descender in 26.6 frac. pixels */
FT_Pos height; /* text height in 26.6 frac. pixels */
FT_Pos max_advance; /* max horizontal advance, in 26.6 pixels */
} FT_Size_Metrics;
The size metrics structure gives the metrics of a size object.
fields
| x_ppem |
The width of the scaled EM square in pixels, hence the term ‘ppem’ (pixels per EM). It is also referred to as ‘nominal width’. |
| y_ppem |
The height of the scaled EM square in pixels, hence the term ‘ppem’ (pixels per EM). It is also referred to as ‘nominal height’. |
| x_scale |
A 16.16 fractional scaling value to convert horizontal metrics from font units to 26.6 fractional pixels. Only relevant for scalable font formats. |
| y_scale |
A 16.16 fractional scaling value to convert vertical metrics from font units to 26.6 fractional pixels. Only relevant for scalable font formats. |
| ascender |
The ascender in 26.6 fractional pixels, rounded up to an integer value. See |
| descender |
The descender in 26.6 fractional pixels, rounded down to an integer value. See |
| height |
The height in 26.6 fractional pixels, rounded to an integer value. See |
| max_advance |
The maximum advance width in 26.6 fractional pixels, rounded to an integer value. See |
note
The scaling values, if relevant, are determined first during a size changing operation. The remaining fields are then set by the driver. For scalable formats, they are usually set to scaled values of the corresponding fields in FT_FaceRec. Some values like ascender or descender are rounded for historical reasons; more precise values (for outline fonts) can be derived by scaling the corresponding FT_FaceRec values manually, with code similar to the following.
scaled_ascender = FT_MulFix( face->ascender,
size_metrics->y_scale );
Note that due to glyph hinting and the selected rendering mode these values are usually not exact; consequently, they must be treated as unreliable with an error margin of at least one pixel!
Indeed, the only way to get the exact metrics is to render all glyphs. As this would be a definite performance hit, it is up to client applications to perform such computations.
The FT_Size_Metrics structure is valid for bitmap fonts also.
TrueType fonts with native bytecode hinting
All applications that handle TrueType fonts with native hinting must be aware that TTFs expect different rounding of vertical font dimensions. The application has to cater for this, especially if it wants to rely on a TTF's vertical data (for example, to properly align box characters vertically).
Only the application knows in advance that it is going to use native hinting for TTFs! FreeType, on the other hand, selects the hinting mode not at the time of creating an FT_Size object but much later, namely while calling FT_Load_Glyph.
Here is some pseudo code that illustrates a possible solution.
font_format = FT_Get_Font_Format( face );
if ( !strcmp( font_format, "TrueType" ) &&
do_native_bytecode_hinting )
{
ascender = ROUND( FT_MulFix( face->ascender,
size_metrics->y_scale ) );
descender = ROUND( FT_MulFix( face->descender,
size_metrics->y_scale ) );
}
else
{
ascender = size_metrics->ascender;
descender = size_metrics->descender;
}
height = size_metrics->height;
max_advance = size_metrics->max_advance;
FT_GlyphSlotRec¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_GlyphSlotRec_
{
FT_Library library;
FT_Face face;
FT_GlyphSlot next;
FT_UInt glyph_index; /* new in 2.10; was reserved previously */
FT_Generic generic;
FT_Glyph_Metrics metrics;
FT_Fixed linearHoriAdvance;
FT_Fixed linearVertAdvance;
FT_Vector advance;
FT_Glyph_Format format;
FT_Bitmap bitmap;
FT_Int bitmap_left;
FT_Int bitmap_top;
FT_Outline outline;
FT_UInt num_subglyphs;
FT_SubGlyph subglyphs;
void* control_data;
long control_len;
FT_Pos lsb_delta;
FT_Pos rsb_delta;
void* other;
FT_Slot_Internal internal;
} FT_GlyphSlotRec;
FreeType root glyph slot class structure. A glyph slot is a container where individual glyphs can be loaded, be they in outline or bitmap format.
fields
| library |
A handle to the FreeType library instance this slot belongs to. |
| face |
A handle to the parent face object. |
| next |
In some cases (like some font tools), several glyph slots per face object can be a good thing. As this is rare, the glyph slots are listed through a direct, single-linked list using its |
| glyph_index |
[Since 2.10] The glyph index passed as an argument to |
| generic |
A typeless pointer unused by the FreeType library or any of its drivers. It can be used by client applications to link their own data to each glyph slot object. |
| metrics |
The metrics of the last loaded glyph in the slot. The returned values depend on the last load flags (see the Note that even when the glyph image is transformed, the metrics are not. |
| linearHoriAdvance |
The advance width of the unhinted glyph. Its value is expressed in 16.16 fractional pixels, unless |
| linearVertAdvance |
The advance height of the unhinted glyph. Its value is expressed in 16.16 fractional pixels, unless |
| advance |
This shorthand is, depending on |
| format |
This field indicates the format of the image contained in the glyph slot. Typically |
| bitmap |
This field is used as a bitmap descriptor. Note that the address and content of the bitmap buffer can change between calls of |
| bitmap_left |
The bitmap's left bearing expressed in integer pixels. |
| bitmap_top |
The bitmap's top bearing expressed in integer pixels. This is the distance from the baseline to the top-most glyph scanline, upwards y coordinates being positive. |
| outline |
The outline descriptor for the current glyph image if its format is [Since 2.10.1] If |
| num_subglyphs |
The number of subglyphs in a composite glyph. This field is only valid for the composite glyph format that should normally only be loaded with the |
| subglyphs |
An array of subglyph descriptors for composite glyphs. There are |
| control_data |
Certain font drivers can also return the control data for a given glyph image (e.g. TrueType bytecode, Type 1 charstrings, etc.). This field is a pointer to such data; it is currently internal to FreeType. |
| control_len |
This is the length in bytes of the control data. Currently internal to FreeType. |
| other |
Reserved. |
| lsb_delta |
The difference between hinted and unhinted left side bearing while auto-hinting is active. Zero otherwise. |
| rsb_delta |
The difference between hinted and unhinted right side bearing while auto-hinting is active. Zero otherwise. |
note
If FT_Load_Glyph is called with default flags (see FT_LOAD_DEFAULT) the glyph image is loaded in the glyph slot in its native format (e.g., an outline glyph for TrueType and Type 1 formats). [Since 2.9] The prospective bitmap metrics are calculated according to FT_LOAD_TARGET_XXX and other flags even for the outline glyph, even if FT_LOAD_RENDER is not set.
This image can later be converted into a bitmap by calling FT_Render_Glyph. This function searches the current renderer for the native image's format, then invokes it.
The renderer is in charge of transforming the native image through the slot's face transformation fields, then converting it into a bitmap that is returned in slot->bitmap.
Note that slot->bitmap_left and slot->bitmap_top are also used to specify the position of the bitmap relative to the current pen position (e.g., coordinates (0,0) on the baseline). Of course, slot->format is also changed to FT_GLYPH_FORMAT_BITMAP.
Here is a small pseudo code fragment that shows how to use lsb_delta and rsb_delta to do fractional positioning of glyphs:
FT_GlyphSlot slot = face->glyph;
FT_Pos origin_x = 0;
for all glyphs do
<load glyph with `FT_Load_Glyph'>
FT_Outline_Translate( slot->outline, origin_x & 63, 0 );
<save glyph image, or render glyph, or ...>
<compute kern between current and next glyph
and add it to `origin_x'>
origin_x += slot->advance.x;
origin_x += slot->lsb_delta - slot->rsb_delta;
endfor
Here is another small pseudo code fragment that shows how to use lsb_delta and rsb_delta to improve integer positioning of glyphs:
FT_GlyphSlot slot = face->glyph;
FT_Pos origin_x = 0;
FT_Pos prev_rsb_delta = 0;
for all glyphs do
<compute kern between current and previous glyph
and add it to `origin_x'>
<load glyph with `FT_Load_Glyph'>
if ( prev_rsb_delta - slot->lsb_delta > 32 )
origin_x -= 64;
else if ( prev_rsb_delta - slot->lsb_delta < -31 )
origin_x += 64;
prev_rsb_delta = slot->rsb_delta;
<save glyph image, or render glyph, or ...>
origin_x += slot->advance.x;
endfor
If you use strong auto-hinting, you must apply these delta values! Otherwise you will experience far too large inter-glyph spacing at small rendering sizes in most cases. Note that it doesn't harm to use the above code for other hinting modes also, since the delta values are zero then.
FT_Glyph_Metrics¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Glyph_Metrics_
{
FT_Pos width;
FT_Pos height;
FT_Pos horiBearingX;
FT_Pos horiBearingY;
FT_Pos horiAdvance;
FT_Pos vertBearingX;
FT_Pos vertBearingY;
FT_Pos vertAdvance;
} FT_Glyph_Metrics;
A structure to model the metrics of a single glyph. The values are expressed in 26.6 fractional pixel format; if the flag FT_LOAD_NO_SCALE has been used while loading the glyph, values are expressed in font units instead.
fields
| width |
The glyph's width. |
| height |
The glyph's height. |
| horiBearingX |
Left side bearing for horizontal layout. |
| horiBearingY |
Top side bearing for horizontal layout. |
| horiAdvance |
Advance width for horizontal layout. |
| vertBearingX |
Left side bearing for vertical layout. |
| vertBearingY |
Top side bearing for vertical layout. Larger positive values mean further below the vertical glyph origin. |
| vertAdvance |
Advance height for vertical layout. Positive values mean the glyph has a positive advance downward. |
note
If not disabled with FT_LOAD_NO_HINTING, the values represent dimensions of the hinted glyph (in case hinting is applicable).
Stroking a glyph with an outside border does not increase horiAdvance or vertAdvance; you have to manually adjust these values to account for the added width and height.
FreeType doesn't use the ‘VORG’ table data for CFF fonts because it doesn't have an interface to quickly retrieve the glyph height. The y coordinate of the vertical origin can be simply computed as vertBearingY + height after loading a glyph.
FT_SubGlyph¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_SubGlyphRec_* FT_SubGlyph;
The subglyph structure is an internal object used to describe subglyphs (for example, in the case of composites).
note
The subglyph implementation is not part of the high-level API, hence the forward structure declaration.
You can however retrieve subglyph information with FT_Get_SubGlyph_Info.
FT_Bitmap_Size¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Bitmap_Size_
{
FT_Short height;
FT_Short width;
FT_Pos size;
FT_Pos x_ppem;
FT_Pos y_ppem;
} FT_Bitmap_Size;
This structure models the metrics of a bitmap strike (i.e., a set of glyphs for a given point size and resolution) in a bitmap font. It is used for the available_sizes field of FT_Face.
fields
| height |
The vertical distance, in pixels, between two consecutive baselines. It is always positive. |
| width |
The average width, in pixels, of all glyphs in the strike. |
| size |
The nominal size of the strike in 26.6 fractional points. This field is not very useful. |
| x_ppem |
The horizontal ppem (nominal width) in 26.6 fractional pixels. |
| y_ppem |
The vertical ppem (nominal height) in 26.6 fractional pixels. |
note
Windows FNT: The nominal size given in a FNT font is not reliable. If the driver finds it incorrect, it sets size to some calculated values, and x_ppem and y_ppem to the pixel width and height given in the font, respectively.
TrueType embedded bitmaps: size, width, and height values are not contained in the bitmap strike itself. They are computed from the global font parameters.
FT_Init_FreeType¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Init_FreeType( FT_Library *alibrary );
Initialize a new FreeType library object. The set of modules that are registered by this function is determined at build time.
output
| alibrary |
A handle to a new library object. |
return
FreeType error code. 0 means success.
note
In case you want to provide your own memory allocating routines, use FT_New_Library instead, followed by a call to FT_Add_Default_Modules (or a series of calls to FT_Add_Module) and FT_Set_Default_Properties.
See the documentation of FT_Library and FT_Face for multi-threading issues.
If you need reference-counting (cf. FT_Reference_Library), use FT_New_Library and FT_Done_Library.
If compilation option FT_CONFIG_OPTION_ENVIRONMENT_PROPERTIES is set, this function reads the FREETYPE_PROPERTIES environment variable to control driver properties. See section ‘Driver properties’ for more.
FT_Done_FreeType¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Done_FreeType( FT_Library library );
Destroy a given FreeType library object and all of its children, including resources, drivers, faces, sizes, etc.
input
| library |
A handle to the target library object. |
return
FreeType error code. 0 means success.
FT_New_Face¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_New_Face( FT_Library library,
const char* filepathname,
FT_Long face_index,
FT_Face *aface );
Call FT_Open_Face to open a font by its pathname.
inout
| library |
A handle to the library resource. |
input
| pathname |
A path to the font file. |
| face_index |
See |
output
| aface |
A handle to a new face object. If |
return
FreeType error code. 0 means success.
note
Use FT_Done_Face to destroy the created FT_Face object (along with its slot and sizes).
FT_Done_Face¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Discard a given face object, as well as all of its child slots and sizes.
input
| face |
A handle to a target face object. |
return
FreeType error code. 0 means success.
note
See the discussion of reference counters in the description of FT_Reference_Face.
FT_Reference_Face¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
A counter gets initialized to 1 at the time an FT_Face structure is created. This function increments the counter. FT_Done_Face then only destroys a face if the counter is 1, otherwise it simply decrements the counter.
This function helps in managing life-cycles of structures that reference FT_Face objects.
input
| face |
A handle to a target face object. |
return
FreeType error code. 0 means success.
since
2.4.2
FT_New_Memory_Face¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_New_Memory_Face( FT_Library library,
const FT_Byte* file_base,
FT_Long file_size,
FT_Long face_index,
FT_Face *aface );
Call FT_Open_Face to open a font that has been loaded into memory.
inout
| library |
A handle to the library resource. |
input
| file_base |
A pointer to the beginning of the font data. |
| file_size |
The size of the memory chunk used by the font data. |
| face_index |
See |
output
| aface |
A handle to a new face object. If |
return
FreeType error code. 0 means success.
note
You must not deallocate the memory before calling FT_Done_Face.
FT_Face_Properties¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Face_Properties( FT_Face face,
FT_UInt num_properties,
FT_Parameter* properties );
Set or override certain (library or module-wide) properties on a face-by-face basis. Useful for finer-grained control and avoiding locks on shared structures (threads can modify their own faces as they see fit).
Contrary to FT_Property_Set, this function uses FT_Parameter so that you can pass multiple properties to the target face in one call. Note that only a subset of the available properties can be controlled.
-
FT_PARAM_TAG_STEM_DARKENING(stem darkening, corresponding to the propertyno-stem-darkeningprovided by the ‘autofit’, ‘cff’, ‘type1’, and ‘t1cid’ modules; seeno-stem-darkening). -
FT_PARAM_TAG_LCD_FILTER_WEIGHTS(LCD filter weights, corresponding to functionFT_Library_SetLcdFilterWeights). -
FT_PARAM_TAG_RANDOM_SEED(seed value for the CFF, Type 1, and CID ‘random’ operator, corresponding to therandom-seedproperty provided by the ‘cff’, ‘type1’, and ‘t1cid’ modules; seerandom-seed).
Pass NULL as data in FT_Parameter for a given tag to reset the option and use the library or module default again.
input
| face |
A handle to the source face object. |
| num_properties |
The number of properties that follow. |
| properties |
A handle to an |
return
FreeType error code. 0 means success.
example
Here is an example that sets three properties. You must define FT_CONFIG_OPTION_SUBPIXEL_RENDERING to make the LCD filter examples work.
FT_Parameter property1;
FT_Bool darken_stems = 1;
FT_Parameter property2;
FT_LcdFiveTapFilter custom_weight =
{ 0x11, 0x44, 0x56, 0x44, 0x11 };
FT_Parameter property3;
FT_Int32 random_seed = 314159265;
FT_Parameter properties[3] = { property1,
property2,
property3 };
property1.tag = FT_PARAM_TAG_STEM_DARKENING;
property1.data = &darken_stems;
property2.tag = FT_PARAM_TAG_LCD_FILTER_WEIGHTS;
property2.data = custom_weight;
property3.tag = FT_PARAM_TAG_RANDOM_SEED;
property3.data = &random_seed;
FT_Face_Properties( face, 3, properties );
The next example resets a single property to its default value.
FT_Parameter property;
property.tag = FT_PARAM_TAG_LCD_FILTER_WEIGHTS;
property.data = NULL;
FT_Face_Properties( face, 1, &property );
since
2.8
FT_Open_Face¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Open_Face( FT_Library library,
const FT_Open_Args* args,
FT_Long face_index,
FT_Face *aface );
Create a face object from a given resource described by FT_Open_Args.
inout
| library |
A handle to the library resource. |
input
| args |
A pointer to an |
| face_index |
This field holds two different values. Bits 0-15 are the index of the face in the font file (starting with value 0). Set it to 0 if there is only one face in the font file. [Since 2.6.1] Bits 16-30 are relevant to GX and OpenType variation fonts only, specifying the named instance index for the current face index (starting with value 1; value 0 makes FreeType ignore named instances). For non-variation fonts, bits 16-30 are ignored. Assuming that you want to access the third named instance in face 4,
|
output
| aface |
A handle to a new face object. If |
return
FreeType error code. 0 means success.
note
Unlike FreeType 1.x, this function automatically creates a glyph slot for the face object that can be accessed directly through face->glyph.
Each new face object created with this function also owns a default FT_Size object, accessible as face->size.
One FT_Library instance can have multiple face objects, this is, FT_Open_Face and its siblings can be called multiple times using the same library argument.
See the discussion of reference counters in the description of FT_Reference_Face.
If FT_OPEN_STREAM is set in args->flags, the stream in args->stream is automatically closed before this function returns any error (including FT_Err_Invalid_Argument).
example
To loop over all faces, use code similar to the following snippet (omitting the error handling).
...
FT_Face face;
FT_Long i, num_faces;
error = FT_Open_Face( library, args, -1, &face );
if ( error ) { ... }
num_faces = face->num_faces;
FT_Done_Face( face );
for ( i = 0; i < num_faces; i++ )
{
...
error = FT_Open_Face( library, args, i, &face );
...
FT_Done_Face( face );
...
}
To loop over all valid values for face_index, use something similar to the following snippet, again without error handling. The code accesses all faces immediately (thus only a single call of FT_Open_Face within the do-loop), with and without named instances.
...
FT_Face face;
FT_Long num_faces = 0;
FT_Long num_instances = 0;
FT_Long face_idx = 0;
FT_Long instance_idx = 0;
do
{
FT_Long id = ( instance_idx << 16 ) + face_idx;
error = FT_Open_Face( library, args, id, &face );
if ( error ) { ... }
num_faces = face->num_faces;
num_instances = face->style_flags >> 16;
...
FT_Done_Face( face );
if ( instance_idx < num_instances )
instance_idx++;
else
{
face_idx++;
instance_idx = 0;
}
} while ( face_idx < num_faces )
FT_Open_Args¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Open_Args_
{
FT_UInt flags;
const FT_Byte* memory_base;
FT_Long memory_size;
FT_String* pathname;
FT_Stream stream;
FT_Module driver;
FT_Int num_params;
FT_Parameter* params;
} FT_Open_Args;
A structure to indicate how to open a new font file or stream. A pointer to such a structure can be used as a parameter for the functions FT_Open_Face and FT_Attach_Stream.
fields
| flags |
A set of bit flags indicating how to use the structure. |
| memory_base |
The first byte of the file in memory. |
| memory_size |
The size in bytes of the file in memory. |
| pathname |
A pointer to an 8-bit file pathname. The pointer is not owned by FreeType. |
| stream |
A handle to a source stream object. |
| driver |
This field is exclusively used by |
| num_params |
The number of extra parameters. |
| params |
Extra parameters passed to the font driver when opening a new face. |
note
The stream type is determined by the contents of flags:
If the FT_OPEN_MEMORY bit is set, assume that this is a memory file of memory_size bytes, located at memory_address. The data are not copied, and the client is responsible for releasing and destroying them after the corresponding call to FT_Done_Face.
Otherwise, if the FT_OPEN_STREAM bit is set, assume that a custom input stream stream is used.
Otherwise, if the FT_OPEN_PATHNAME bit is set, assume that this is a normal file and use pathname to open it.
If none of the above bits are set or if multiple are set at the same time, the flags are invalid and FT_Open_Face fails.
If the FT_OPEN_DRIVER bit is set, FT_Open_Face only tries to open the file with the driver whose handler is in driver.
If the FT_OPEN_PARAMS bit is set, the parameters given by num_params and params is used. They are ignored otherwise.
Ideally, both the pathname and params fields should be tagged as ‘const’; this is missing for API backward compatibility. In other words, applications should treat them as read-only.
FT_Parameter¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Parameter_
{
FT_ULong tag;
FT_Pointer data;
} FT_Parameter;
A simple structure to pass more or less generic parameters to FT_Open_Face and FT_Face_Properties.
fields
| tag |
A four-byte identification tag. |
| data |
A pointer to the parameter data. |
note
The ID and function of parameters are driver-specific. See section ‘Parameter Tags’ for more information.
FT_Attach_File¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Call FT_Attach_Stream to attach a file.
inout
| face |
The target face object. |
input
| filepathname |
The pathname. |
return
FreeType error code. 0 means success.
FT_Attach_Stream¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Attach_Stream( FT_Face face,
FT_Open_Args* parameters );
‘Attach’ data to a face object. Normally, this is used to read additional information for the face object. For example, you can attach an AFM file that comes with a Type 1 font to get the kerning values and other metrics.
inout
| face |
The target face object. |
input
| parameters |
A pointer to |
return
FreeType error code. 0 means success.
note
The meaning of the ‘attach’ (i.e., what really happens when the new file is read) is not fixed by FreeType itself. It really depends on the font format (and thus the font driver).
Client applications are expected to know what they are doing when invoking this function. Most drivers simply do not implement file or stream attachments.
FT_Set_Char_Size¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Set_Char_Size( FT_Face face,
FT_F26Dot6 char_width,
FT_F26Dot6 char_height,
FT_UInt horz_resolution,
FT_UInt vert_resolution );
Call FT_Request_Size to request the nominal size (in points).
inout
| face |
A handle to a target face object. |
input
| char_width |
The nominal width, in 26.6 fractional points. |
| char_height |
The nominal height, in 26.6 fractional points. |
| horz_resolution |
The horizontal resolution in dpi. |
| vert_resolution |
The vertical resolution in dpi. |
return
FreeType error code. 0 means success.
note
While this function allows fractional points as input values, the resulting ppem value for the given resolution is always rounded to the nearest integer.
If either the character width or height is zero, it is set equal to the other value.
If either the horizontal or vertical resolution is zero, it is set equal to the other value.
A character width or height smaller than 1pt is set to 1pt; if both resolution values are zero, they are set to 72dpi.
Don't use this function if you are using the FreeType cache API.
FT_Set_Pixel_Sizes¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Set_Pixel_Sizes( FT_Face face,
FT_UInt pixel_width,
FT_UInt pixel_height );
Call FT_Request_Size to request the nominal size (in pixels).
inout
| face |
A handle to the target face object. |
input
| pixel_width |
The nominal width, in pixels. |
| pixel_height |
The nominal height, in pixels. |
return
FreeType error code. 0 means success.
note
You should not rely on the resulting glyphs matching or being constrained to this pixel size. Refer to FT_Request_Size to understand how requested sizes relate to actual sizes.
Don't use this function if you are using the FreeType cache API.
FT_Request_Size¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Request_Size( FT_Face face,
FT_Size_Request req );
Resize the scale of the active FT_Size object in a face.
inout
| face |
A handle to a target face object. |
input
| req |
A pointer to a |
return
FreeType error code. 0 means success.
note
Although drivers may select the bitmap strike matching the request, you should not rely on this if you intend to select a particular bitmap strike. Use FT_Select_Size instead in that case.
The relation between the requested size and the resulting glyph size is dependent entirely on how the size is defined in the source face. The font designer chooses the final size of each glyph relative to this size. For more information refer to ‘https://www.freetype.org/freetype2/docs/glyphs/glyphs-2.html’.
Contrary to FT_Set_Char_Size, this function doesn't have special code to normalize zero-valued widths, heights, or resolutions (which lead to errors in most cases).
Don't use this function if you are using the FreeType cache API.
FT_Select_Size¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Select a bitmap strike. To be more precise, this function sets the scaling factors of the active FT_Size object in a face so that bitmaps from this particular strike are taken by FT_Load_Glyph and friends.
inout
| face |
A handle to a target face object. |
input
| strike_index |
The index of the bitmap strike in the |
return
FreeType error code. 0 means success.
note
For bitmaps embedded in outline fonts it is common that only a subset of the available glyphs at a given ppem value is available. FreeType silently uses outlines if there is no bitmap for a given glyph index.
For GX and OpenType variation fonts, a bitmap strike makes sense only if the default instance is active (this is, no glyph variation takes place); otherwise, FreeType simply ignores bitmap strikes. The same is true for all named instances that are different from the default instance.
Don't use this function if you are using the FreeType cache API.
FT_Size_Request_Type¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef enum FT_Size_Request_Type_
{
FT_SIZE_REQUEST_TYPE_NOMINAL,
FT_SIZE_REQUEST_TYPE_REAL_DIM,
FT_SIZE_REQUEST_TYPE_BBOX,
FT_SIZE_REQUEST_TYPE_CELL,
FT_SIZE_REQUEST_TYPE_SCALES,
FT_SIZE_REQUEST_TYPE_MAX
} FT_Size_Request_Type;
An enumeration type that lists the supported size request types, i.e., what input size (in font units) maps to the requested output size (in pixels, as computed from the arguments of FT_Size_Request).
values
| FT_SIZE_REQUEST_TYPE_NOMINAL |
The nominal size. The This is the standard scaling found in most applications. In particular, use this size request type for TrueType fonts if they provide optical scaling or something similar. Note, however, that |
| FT_SIZE_REQUEST_TYPE_REAL_DIM |
The real dimension. The sum of the |
| FT_SIZE_REQUEST_TYPE_BBOX |
The font bounding box. The width and height of the |
| FT_SIZE_REQUEST_TYPE_CELL |
The |
| FT_SIZE_REQUEST_TYPE_SCALES |
Specify the scaling values directly. |
note
The above descriptions only apply to scalable formats. For bitmap formats, the behaviour is up to the driver.
See the note section of FT_Size_Metrics if you wonder how size requesting relates to scaling values.
FT_Size_RequestRec¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Size_RequestRec_
{
FT_Size_Request_Type type;
FT_Long width;
FT_Long height;
FT_UInt horiResolution;
FT_UInt vertResolution;
} FT_Size_RequestRec;
A structure to model a size request.
fields
| type |
See |
| width |
The desired width, given as a 26.6 fractional point value (with 72pt = 1in). |
| height |
The desired height, given as a 26.6 fractional point value (with 72pt = 1in). |
| horiResolution |
The horizontal resolution (dpi, i.e., pixels per inch). If set to zero, |
| vertResolution |
The vertical resolution (dpi, i.e., pixels per inch). If set to zero, |
note
If width is zero, the horizontal scaling value is set equal to the vertical scaling value, and vice versa.
If type is FT_SIZE_REQUEST_TYPE_SCALES, width and height are interpreted directly as 16.16 fractional scaling values, without any further modification, and both horiResolution and vertResolution are ignored.
FT_Size_Request¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Size_RequestRec_ *FT_Size_Request;
A handle to a size request structure.
FT_Set_Transform¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Set the transformation that is applied to glyph images when they are loaded into a glyph slot through FT_Load_Glyph.
inout
| face |
A handle to the source face object. |
input
| matrix |
A pointer to the transformation's 2x2 matrix. Use |
| delta |
A pointer to the translation vector. Use |
note
This function is provided as a convenience, but keep in mind that FT_Matrix coefficients are only 16.16 fixed-point values, which can limit the accuracy of the results. Using floating-point computations to perform the transform directly in client code instead will always yield better numbers.
The transformation is only applied to scalable image formats after the glyph has been loaded. It means that hinting is unaltered by the transformation and is performed on the character size given in the last call to FT_Set_Char_Size or FT_Set_Pixel_Sizes.
Note that this also transforms the face.glyph.advance field, but not the values in face.glyph.metrics.
FT_Get_Transform¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Return the transformation that is applied to glyph images when they are loaded into a glyph slot through FT_Load_Glyph. See FT_Set_Transform for more details.
input
| face |
A handle to the source face object. |
output
| matrix |
A pointer to a transformation's 2x2 matrix. Set this to NULL if you are not interested in the value. |
| delta |
A pointer a translation vector. Set this to NULL if you are not interested in the value. |
since
2.11
FT_Load_Glyph¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Load a glyph into the glyph slot of a face object.
inout
| face |
A handle to the target face object where the glyph is loaded. |
input
| glyph_index |
The index of the glyph in the font file. For CID-keyed fonts (either in PS or in CFF format) this argument specifies the CID value. |
| load_flags |
A flag indicating what to load for this glyph. The |
return
FreeType error code. 0 means success.
note
The loaded glyph may be transformed. See FT_Set_Transform for the details.
For subsetted CID-keyed fonts, FT_Err_Invalid_Argument is returned for invalid CID values (this is, for CID values that don't have a corresponding glyph in the font). See the discussion of the FT_FACE_FLAG_CID_KEYED flag for more details.
If you receive FT_Err_Glyph_Too_Big, try getting the glyph outline at EM size, then scale it manually and fill it as a graphics operation.
FT_Get_Char_Index¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Return the glyph index of a given character code. This function uses the currently selected charmap to do the mapping.
input
| face |
A handle to the source face object. |
| charcode |
The character code. |
return
The glyph index. 0 means ‘undefined character code’.
note
If you use FreeType to manipulate the contents of font files directly, be aware that the glyph index returned by this function doesn't always correspond to the internal indices used within the file. This is done to ensure that value 0 always corresponds to the ‘missing glyph’. If the first glyph is not named ‘.notdef’, then for Type 1 and Type 42 fonts, ‘.notdef’ will be moved into the glyph ID 0 position, and whatever was there will be moved to the position ‘.notdef’ had. For Type 1 fonts, if there is no ‘.notdef’ glyph at all, then one will be created at index 0 and whatever was there will be moved to the last index – Type 42 fonts are considered invalid under this condition.
FT_Get_First_Char¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Return the first character code in the current charmap of a given face, together with its corresponding glyph index.
input
| face |
A handle to the source face object. |
output
| agindex |
Glyph index of first character code. 0 if charmap is empty. |
return
The charmap's first character code.
note
You should use this function together with FT_Get_Next_Char to parse all character codes available in a given charmap. The code should look like this:
FT_ULong charcode;
FT_UInt gindex;
charcode = FT_Get_First_Char( face, &gindex );
while ( gindex != 0 )
{
... do something with (charcode,gindex) pair ...
charcode = FT_Get_Next_Char( face, charcode, &gindex );
}
Be aware that character codes can have values up to 0xFFFFFFFF; this might happen for non-Unicode or malformed cmaps. However, even with regular Unicode encoding, so-called ‘last resort fonts’ (using SFNT cmap format 13, see function FT_Get_CMap_Format) normally have entries for all Unicode characters up to 0x1FFFFF, which can cause a lot of iterations.
Note that *agindex is set to 0 if the charmap is empty. The result itself can be 0 in two cases: if the charmap is empty or if the value 0 is the first valid character code.
FT_Get_Next_Char¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Return the next character code in the current charmap of a given face following the value char_code, as well as the corresponding glyph index.
input
| face |
A handle to the source face object. |
| char_code |
The starting character code. |
output
| agindex |
Glyph index of next character code. 0 if charmap is empty. |
return
The charmap's next character code.
note
You should use this function with FT_Get_First_Char to walk over all character codes available in a given charmap. See the note for that function for a simple code example.
Note that *agindex is set to 0 when there are no more codes in the charmap.
FT_Get_Name_Index¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Return the glyph index of a given glyph name.
input
| face |
A handle to the source face object. |
| glyph_name |
The glyph name. |
return
The glyph index. 0 means ‘undefined character code’.
FT_Load_Char¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Load a glyph into the glyph slot of a face object, accessed by its character code.
inout
| face |
A handle to a target face object where the glyph is loaded. |
input
| char_code |
The glyph's character code, according to the current charmap used in the face. |
| load_flags |
A flag indicating what to load for this glyph. The |
return
FreeType error code. 0 means success.
note
This function simply calls FT_Get_Char_Index and FT_Load_Glyph.
Many fonts contain glyphs that can't be loaded by this function since its glyph indices are not listed in any of the font's charmaps.
If no active cmap is set up (i.e., face->charmap is zero), the call to FT_Get_Char_Index is omitted, and the function behaves identically to FT_Load_Glyph.
FT_LOAD_TARGET_MODE¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_LOAD_TARGET_MODE( x ) ( (FT_Render_Mode)( ( (x) >> 16 ) & 15 ) )
Return the FT_Render_Mode corresponding to a given FT_LOAD_TARGET_XXX value.
FT_Render_Glyph¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Render_Glyph( FT_GlyphSlot slot,
FT_Render_Mode render_mode );
Convert a given glyph image to a bitmap. It does so by inspecting the glyph image format, finding the relevant renderer, and invoking it.
inout
| slot |
A handle to the glyph slot containing the image to convert. |
input
| render_mode |
The render mode used to render the glyph image into a bitmap. See If |
return
FreeType error code. 0 means success.
note
To get meaningful results, font scaling values must be set with functions like FT_Set_Char_Size before calling FT_Render_Glyph.
When FreeType outputs a bitmap of a glyph, it really outputs an alpha coverage map. If a pixel is completely covered by a filled-in outline, the bitmap contains 0xFF at that pixel, meaning that 0xFF/0xFF fraction of that pixel is covered, meaning the pixel is 100% black (or 0% bright). If a pixel is only 50% covered (value 0x80), the pixel is made 50% black (50% bright or a middle shade of grey). 0% covered means 0% black (100% bright or white).
On high-DPI screens like on smartphones and tablets, the pixels are so small that their chance of being completely covered and therefore completely black are fairly good. On the low-DPI screens, however, the situation is different. The pixels are too large for most of the details of a glyph and shades of gray are the norm rather than the exception.
This is relevant because all our screens have a second problem: they are not linear. 1 + 1 is not 2. Twice the value does not result in twice the brightness. When a pixel is only 50% covered, the coverage map says 50% black, and this translates to a pixel value of 128 when you use 8 bits per channel (0-255). However, this does not translate to 50% brightness for that pixel on our sRGB and gamma 2.2 screens. Due to their non-linearity, they dwell longer in the darks and only a pixel value of about 186 results in 50% brightness – 128 ends up too dark on both bright and dark backgrounds. The net result is that dark text looks burnt-out, pixely and blotchy on bright background, bright text too frail on dark backgrounds, and colored text on colored background (for example, red on green) seems to have dark halos or ‘dirt’ around it. The situation is especially ugly for diagonal stems like in ‘w’ glyph shapes where the quality of FreeType's anti-aliasing depends on the correct display of grays. On high-DPI screens where smaller, fully black pixels reign supreme, this doesn't matter, but on our low-DPI screens with all the gray shades, it does. 0% and 100% brightness are the same things in linear and non-linear space, just all the shades in-between aren't.
The blending function for placing text over a background is
dst = alpha * src + (1 - alpha) * dst ,
which is known as the OVER operator.
To correctly composite an anti-aliased pixel of a glyph onto a surface,
-
take the foreground and background colors (e.g., in sRGB space) and apply gamma to get them in a linear space,
-
use OVER to blend the two linear colors using the glyph pixel as the alpha value (remember, the glyph bitmap is an alpha coverage bitmap), and
-
apply inverse gamma to the blended pixel and write it back to the image.
Internal testing at Adobe found that a target inverse gamma of 1.8 for step 3 gives good results across a wide range of displays with an sRGB gamma curve or a similar one.
This process can cost performance. There is an approximation that does not need to know about the background color; see https://bel.fi/alankila/lcd/ and https://bel.fi/alankila/lcd/alpcor.html for details.
ATTENTION: Linear blending is even more important when dealing with subpixel-rendered glyphs to prevent color-fringing! A subpixel-rendered glyph must first be filtered with a filter that gives equal weight to the three color primaries and does not exceed a sum of 0x100, see section ‘Subpixel Rendering’. Then the only difference to gray linear blending is that subpixel-rendered linear blending is done 3 times per pixel: red foreground subpixel to red background subpixel and so on for green and blue.
FT_Render_Mode¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef enum FT_Render_Mode_
{
FT_RENDER_MODE_NORMAL = 0,
FT_RENDER_MODE_LIGHT,
FT_RENDER_MODE_MONO,
FT_RENDER_MODE_LCD,
FT_RENDER_MODE_LCD_V,
FT_RENDER_MODE_SDF,
FT_RENDER_MODE_MAX
} FT_Render_Mode;
/* these constants are deprecated; use the corresponding */
/* `FT_Render_Mode` values instead */
#define ft_render_mode_normal FT_RENDER_MODE_NORMAL
#define ft_render_mode_mono FT_RENDER_MODE_MONO
Render modes supported by FreeType 2. Each mode corresponds to a specific type of scanline conversion performed on the outline.
For bitmap fonts and embedded bitmaps the bitmap->pixel_mode field in the FT_GlyphSlotRec structure gives the format of the returned bitmap.
All modes except FT_RENDER_MODE_MONO use 256 levels of opacity, indicating pixel coverage. Use linear alpha blending and gamma correction to correctly render non-monochrome glyph bitmaps onto a surface; see FT_Render_Glyph.
The FT_RENDER_MODE_SDF is a special render mode that uses up to 256 distance values, indicating the signed distance from the grid position to the nearest outline.
values
| FT_RENDER_MODE_NORMAL |
Default render mode; it corresponds to 8-bit anti-aliased bitmaps. |
| FT_RENDER_MODE_LIGHT |
This is equivalent to |
| FT_RENDER_MODE_MONO |
This mode corresponds to 1-bit bitmaps (with 2 levels of opacity). |
| FT_RENDER_MODE_LCD |
This mode corresponds to horizontal RGB and BGR subpixel displays like LCD screens. It produces 8-bit bitmaps that are 3 times the width of the original glyph outline in pixels, and which use the |
| FT_RENDER_MODE_LCD_V |
This mode corresponds to vertical RGB and BGR subpixel displays (like PDA screens, rotated LCD displays, etc.). It produces 8-bit bitmaps that are 3 times the height of the original glyph outline in pixels and use the |
| FT_RENDER_MODE_SDF |
This mode corresponds to 8-bit, single-channel signed distance field (SDF) bitmaps. Each pixel in the SDF grid is the value from the pixel's position to the nearest glyph's outline. The distances are calculated from the center of the pixel and are positive if they are filled by the outline (i.e., inside the outline) and negative otherwise. Check the note below on how to convert the output values to usable data. |
note
The selected render mode only affects vector glyphs of a font. Embedded bitmaps often have a different pixel mode like FT_PIXEL_MODE_MONO. You can use FT_Bitmap_Convert to transform them into 8-bit pixmaps.
For FT_RENDER_MODE_SDF the output bitmap buffer contains normalized distances that are packed into unsigned 8-bit values. To get pixel values in floating point representation use the following pseudo-C code for the conversion.
// Load glyph and render using FT_RENDER_MODE_SDF,
// then use the output buffer as follows.
...
FT_Byte buffer = glyph->bitmap->buffer;
for pixel in buffer
{
// `sd` is the signed distance and `spread` is the current spread;
// the default spread is 2 and can be changed.
float sd = (float)pixel - 128.0f;
// Convert to pixel values.
sd = ( sd / 128.0f ) * spread;
// Store `sd` in a buffer or use as required.
}
FT_Get_Kerning¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Get_Kerning( FT_Face face,
FT_UInt left_glyph,
FT_UInt right_glyph,
FT_UInt kern_mode,
FT_Vector *akerning );
Return the kerning vector between two glyphs of the same face.
input
| face |
A handle to a source face object. |
| left_glyph |
The index of the left glyph in the kern pair. |
| right_glyph |
The index of the right glyph in the kern pair. |
| kern_mode |
See |
output
| akerning |
The kerning vector. This is either in font units, fractional pixels (26.6 format), or pixels for scalable formats, and in pixels for fixed-sizes formats. |
return
FreeType error code. 0 means success.
note
Only horizontal layouts (left-to-right & right-to-left) are supported by this method. Other layouts, or more sophisticated kernings, are out of the scope of this API function – they can be implemented through format-specific interfaces.
Kerning for OpenType fonts implemented in a ‘GPOS’ table is not supported; use FT_HAS_KERNING to find out whether a font has data that can be extracted with FT_Get_Kerning.
FT_Kerning_Mode¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef enum FT_Kerning_Mode_
{
FT_KERNING_DEFAULT = 0,
FT_KERNING_UNFITTED,
FT_KERNING_UNSCALED
} FT_Kerning_Mode;
/* these constants are deprecated; use the corresponding */
/* `FT_Kerning_Mode` values instead */
#define ft_kerning_default FT_KERNING_DEFAULT
#define ft_kerning_unfitted FT_KERNING_UNFITTED
#define ft_kerning_unscaled FT_KERNING_UNSCALED
An enumeration to specify the format of kerning values returned by FT_Get_Kerning.
values
| FT_KERNING_DEFAULT |
Return grid-fitted kerning distances in 26.6 fractional pixels. |
| FT_KERNING_UNFITTED |
Return un-grid-fitted kerning distances in 26.6 fractional pixels. |
| FT_KERNING_UNSCALED |
Return the kerning vector in original font units. |
note
FT_KERNING_DEFAULT returns full pixel values; it also makes FreeType heuristically scale down kerning distances at small ppem values so that they don't become too big.
Both FT_KERNING_DEFAULT and FT_KERNING_UNFITTED use the current horizontal scaling factor (as set e.g. with FT_Set_Char_Size) to convert font units to pixels.
FT_Get_Track_Kerning¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Get_Track_Kerning( FT_Face face,
FT_Fixed point_size,
FT_Int degree,
FT_Fixed* akerning );
Return the track kerning for a given face object at a given size.
input
| face |
A handle to a source face object. |
| point_size |
The point size in 16.16 fractional points. |
| degree |
The degree of tightness. Increasingly negative values represent tighter track kerning, while increasingly positive values represent looser track kerning. Value zero means no track kerning. |
output
| akerning |
The kerning in 16.16 fractional points, to be uniformly applied between all glyphs. |
return
FreeType error code. 0 means success.
note
Currently, only the Type 1 font driver supports track kerning, using data from AFM files (if attached with FT_Attach_File or FT_Attach_Stream).
Only very few AFM files come with track kerning data; please refer to Adobe's AFM specification for more details.
FT_Get_Glyph_Name¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Get_Glyph_Name( FT_Face face,
FT_UInt glyph_index,
FT_Pointer buffer,
FT_UInt buffer_max );
Retrieve the ASCII name of a given glyph in a face. This only works for those faces where FT_HAS_GLYPH_NAMES(face) returns 1.
input
| face |
A handle to a source face object. |
| glyph_index |
The glyph index. |
| buffer_max |
The maximum number of bytes available in the buffer. |
output
| buffer |
A pointer to a target buffer where the name is copied to. |
return
FreeType error code. 0 means success.
note
An error is returned if the face doesn't provide glyph names or if the glyph index is invalid. In all cases of failure, the first byte of buffer is set to 0 to indicate an empty name.
The glyph name is truncated to fit within the buffer if it is too long. The returned string is always zero-terminated.
Be aware that FreeType reorders glyph indices internally so that glyph index 0 always corresponds to the ‘missing glyph’ (called ‘.notdef’).
This function always returns an error if the config macro FT_CONFIG_OPTION_NO_GLYPH_NAMES is not defined in ftoption.h.
FT_Get_Postscript_Name¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( const char* )
FT_Get_Postscript_Name( FT_Face face );
Retrieve the ASCII PostScript name of a given face, if available. This only works with PostScript, TrueType, and OpenType fonts.
input
| face |
A handle to the source face object. |
return
A pointer to the face's PostScript name. NULL if unavailable.
note
The returned pointer is owned by the face and is destroyed with it.
For variation fonts, this string changes if you select a different instance, and you have to call FT_Get_PostScript_Name again to retrieve it. FreeType follows Adobe TechNote #5902, ‘Generating PostScript Names for Fonts Using OpenType Font Variations’.
https://download.macromedia.com/pub/developer/opentype/tech-notes/5902.AdobePSNameGeneration.html
[Since 2.9] Special PostScript names for named instances are only returned if the named instance is set with FT_Set_Named_Instance (and the font has corresponding entries in its ‘fvar’ table). If FT_IS_VARIATION returns true, the algorithmically derived PostScript name is provided, not looking up special entries for named instances.
FT_CharMapRec¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_CharMapRec_
{
FT_Face face;
FT_Encoding encoding;
FT_UShort platform_id;
FT_UShort encoding_id;
} FT_CharMapRec;
The base charmap structure.
fields
| face |
A handle to the parent face object. |
| encoding |
An |
| platform_id |
An ID number describing the platform for the following encoding ID. This comes directly from the TrueType specification and gets emulated for other formats. |
| encoding_id |
A platform-specific encoding number. This also comes from the TrueType specification and gets emulated similarly. |
FT_Select_Charmap¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Select_Charmap( FT_Face face,
FT_Encoding encoding );
Select a given charmap by its encoding tag (as listed in freetype.h).
inout
| face |
A handle to the source face object. |
input
| encoding |
A handle to the selected encoding. |
return
FreeType error code. 0 means success.
note
This function returns an error if no charmap in the face corresponds to the encoding queried here.
Because many fonts contain more than a single cmap for Unicode encoding, this function has some special code to select the one that covers Unicode best (‘best’ in the sense that a UCS-4 cmap is preferred to a UCS-2 cmap). It is thus preferable to FT_Set_Charmap in this case.
FT_Set_Charmap¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Set_Charmap( FT_Face face,
FT_CharMap charmap );
Select a given charmap for character code to glyph index mapping.
inout
| face |
A handle to the source face object. |
input
| charmap |
A handle to the selected charmap. |
return
FreeType error code. 0 means success.
note
This function returns an error if the charmap is not part of the face (i.e., if it is not listed in the face->charmaps table).
It also fails if an OpenType type 14 charmap is selected (which doesn't map character codes to glyph indices at all).
FT_Get_Charmap_Index¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Int )
FT_Get_Charmap_Index( FT_CharMap charmap );
Retrieve index of a given charmap.
input
| charmap |
A handle to a charmap. |
return
The index into the array of character maps within the face to which charmap belongs. If an error occurs, -1 is returned.
FT_Get_FSType_Flags¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
Return the fsType flags for a font.
input
| face |
A handle to the source face object. |
return
The fsType flags, see FT_FSTYPE_XXX.
note
Use this function rather than directly reading the fs_type field in the PS_FontInfoRec structure, which is only guaranteed to return the correct results for Type 1 fonts.
since
2.3.8
FT_Get_SubGlyph_Info¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
FT_EXPORT( FT_Error )
FT_Get_SubGlyph_Info( FT_GlyphSlot glyph,
FT_UInt sub_index,
FT_Int *p_index,
FT_UInt *p_flags,
FT_Int *p_arg1,
FT_Int *p_arg2,
FT_Matrix *p_transform );
Retrieve a description of a given subglyph. Only use it if glyph->format is FT_GLYPH_FORMAT_COMPOSITE; an error is returned otherwise.
input
| glyph |
The source glyph slot. |
| sub_index |
The index of the subglyph. Must be less than |
output
| p_index |
The glyph index of the subglyph. |
| p_flags |
The subglyph flags, see |
| p_arg1 |
The subglyph's first argument (if any). |
| p_arg2 |
The subglyph's second argument (if any). |
| p_transform |
The subglyph transformation (if any). |
return
FreeType error code. 0 means success.
note
The values of *p_arg1, *p_arg2, and *p_transform must be interpreted depending on the flags returned in *p_flags. See the OpenType specification for details.
https://docs.microsoft.com/en-us/typography/opentype/spec/glyf#composite-glyph-description
FT_Face_Internal¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Face_InternalRec_* FT_Face_Internal;
An opaque handle to an FT_Face_InternalRec structure that models the private data of a given FT_Face object.
This structure might change between releases of FreeType 2 and is not generally available to client applications.
FT_Size_Internal¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Size_InternalRec_* FT_Size_Internal;
An opaque handle to an FT_Size_InternalRec structure, used to model private data of a given FT_Size object.
FT_Slot_Internal¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
typedef struct FT_Slot_InternalRec_* FT_Slot_Internal;
An opaque handle to an FT_Slot_InternalRec structure, used to model private data of a given FT_GlyphSlot object.
FT_FACE_FLAG_XXX¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_FACE_FLAG_SCALABLE ( 1L << 0 )
#define FT_FACE_FLAG_FIXED_SIZES ( 1L << 1 )
#define FT_FACE_FLAG_FIXED_WIDTH ( 1L << 2 )
#define FT_FACE_FLAG_SFNT ( 1L << 3 )
#define FT_FACE_FLAG_HORIZONTAL ( 1L << 4 )
#define FT_FACE_FLAG_VERTICAL ( 1L << 5 )
#define FT_FACE_FLAG_KERNING ( 1L << 6 )
#define FT_FACE_FLAG_FAST_GLYPHS ( 1L << 7 )
#define FT_FACE_FLAG_MULTIPLE_MASTERS ( 1L << 8 )
#define FT_FACE_FLAG_GLYPH_NAMES ( 1L << 9 )
#define FT_FACE_FLAG_EXTERNAL_STREAM ( 1L << 10 )
#define FT_FACE_FLAG_HINTER ( 1L << 11 )
#define FT_FACE_FLAG_CID_KEYED ( 1L << 12 )
#define FT_FACE_FLAG_TRICKY ( 1L << 13 )
#define FT_FACE_FLAG_COLOR ( 1L << 14 )
#define FT_FACE_FLAG_VARIATION ( 1L << 15 )
A list of bit flags used in the face_flags field of the FT_FaceRec structure. They inform client applications of properties of the corresponding face.
values
| FT_FACE_FLAG_SCALABLE |
The face contains outline glyphs. Note that a face can contain bitmap strikes also, i.e., a face can have both this flag and |
| FT_FACE_FLAG_FIXED_SIZES |
The face contains bitmap strikes. See also the |
| FT_FACE_FLAG_FIXED_WIDTH |
The face contains fixed-width characters (like Courier, Lucida, MonoType, etc.). |
| FT_FACE_FLAG_SFNT |
The face uses the SFNT storage scheme. For now, this means TrueType and OpenType. |
| FT_FACE_FLAG_HORIZONTAL |
The face contains horizontal glyph metrics. This should be set for all common formats. |
| FT_FACE_FLAG_VERTICAL |
The face contains vertical glyph metrics. This is only available in some formats, not all of them. |
| FT_FACE_FLAG_KERNING |
The face contains kerning information. If set, the kerning distance can be retrieved using the function |
| FT_FACE_FLAG_FAST_GLYPHS |
THIS FLAG IS DEPRECATED. DO NOT USE OR TEST IT. |
| FT_FACE_FLAG_MULTIPLE_MASTERS |
The face contains multiple masters and is capable of interpolating between them. Supported formats are Adobe MM, TrueType GX, and OpenType variation fonts. See section ‘Multiple Masters’ for API details. |
| FT_FACE_FLAG_GLYPH_NAMES |
The face contains glyph names, which can be retrieved using |
| FT_FACE_FLAG_EXTERNAL_STREAM |
Used internally by FreeType to indicate that a face's stream was provided by the client application and should not be destroyed when |
| FT_FACE_FLAG_HINTER |
The font driver has a hinting machine of its own. For example, with TrueType fonts, it makes sense to use data from the SFNT ‘gasp’ table only if the native TrueType hinting engine (with the bytecode interpreter) is available and active. |
| FT_FACE_FLAG_CID_KEYED |
The face is CID-keyed. In that case, the face is not accessed by glyph indices but by CID values. For subsetted CID-keyed fonts this has the consequence that not all index values are a valid argument to Note that CID-keyed fonts that are in an SFNT wrapper (this is, all OpenType/CFF fonts) don't have this flag set since the glyphs are accessed in the normal way (using contiguous indices); the ‘CID-ness’ isn't visible to the application. |
| FT_FACE_FLAG_TRICKY |
The face is ‘tricky’, this is, it always needs the font format's native hinting engine to get a reasonable result. A typical example is the old Chinese font It is not possible to auto-hint such fonts using Currently, there are about a dozen TrueType fonts in the list of tricky fonts; they are hard-coded in file |
| FT_FACE_FLAG_COLOR |
[Since 2.5.1] The face has color glyph tables. See |
| FT_FACE_FLAG_VARIATION |
[Since 2.9] Set if the current face (or named instance) has been altered with |
FT_STYLE_FLAG_XXX¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_STYLE_FLAG_ITALIC ( 1 << 0 )
#define FT_STYLE_FLAG_BOLD ( 1 << 1 )
A list of bit flags to indicate the style of a given face. These are used in the style_flags field of FT_FaceRec.
values
| FT_STYLE_FLAG_ITALIC |
The face style is italic or oblique. |
| FT_STYLE_FLAG_BOLD |
The face is bold. |
note
The style information as provided by FreeType is very basic. More details are beyond the scope and should be done on a higher level (for example, by analyzing various fields of the ‘OS/2’ table in SFNT based fonts).
FT_OPEN_XXX¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_OPEN_MEMORY 0x1
#define FT_OPEN_STREAM 0x2
#define FT_OPEN_PATHNAME 0x4
#define FT_OPEN_DRIVER 0x8
#define FT_OPEN_PARAMS 0x10
/* these constants are deprecated; use the corresponding `FT_OPEN_XXX` */
/* values instead */
#define ft_open_memory FT_OPEN_MEMORY
#define ft_open_stream FT_OPEN_STREAM
#define ft_open_pathname FT_OPEN_PATHNAME
#define ft_open_driver FT_OPEN_DRIVER
#define ft_open_params FT_OPEN_PARAMS
A list of bit field constants used within the flags field of the FT_Open_Args structure.
values
| FT_OPEN_MEMORY |
This is a memory-based stream. |
| FT_OPEN_STREAM |
Copy the stream from the |
| FT_OPEN_PATHNAME |
Create a new input stream from a C path name. |
| FT_OPEN_DRIVER |
Use the |
| FT_OPEN_PARAMS |
Use the |
note
The FT_OPEN_MEMORY, FT_OPEN_STREAM, and FT_OPEN_PATHNAME flags are mutually exclusive.
FT_LOAD_XXX¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_LOAD_DEFAULT 0x0
#define FT_LOAD_NO_SCALE ( 1L << 0 )
#define FT_LOAD_NO_HINTING ( 1L << 1 )
#define FT_LOAD_RENDER ( 1L << 2 )
#define FT_LOAD_NO_BITMAP ( 1L << 3 )
#define FT_LOAD_VERTICAL_LAYOUT ( 1L << 4 )
#define FT_LOAD_FORCE_AUTOHINT ( 1L << 5 )
#define FT_LOAD_CROP_BITMAP ( 1L << 6 )
#define FT_LOAD_PEDANTIC ( 1L << 7 )
#define FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH ( 1L << 9 )
#define FT_LOAD_NO_RECURSE ( 1L << 10 )
#define FT_LOAD_IGNORE_TRANSFORM ( 1L << 11 )
#define FT_LOAD_MONOCHROME ( 1L << 12 )
#define FT_LOAD_LINEAR_DESIGN ( 1L << 13 )
#define FT_LOAD_NO_AUTOHINT ( 1L << 15 )
/* Bits 16-19 are used by `FT_LOAD_TARGET_` */
#define FT_LOAD_COLOR ( 1L << 20 )
#define FT_LOAD_COMPUTE_METRICS ( 1L << 21 )
#define FT_LOAD_BITMAP_METRICS_ONLY ( 1L << 22 )
A list of bit field constants for FT_Load_Glyph to indicate what kind of operations to perform during glyph loading.
values
| FT_LOAD_DEFAULT |
Corresponding to 0, this value is used as the default glyph load operation. In this case, the following happens:
Note that by default the glyph loader doesn't render outlines into bitmaps. The following flags are used to modify this default behaviour to more specific and useful cases. |
| FT_LOAD_NO_SCALE |
Don't scale the loaded outline glyph but keep it in font units. This flag implies If the font is ‘tricky’ (see |
| FT_LOAD_NO_HINTING |
Disable hinting. This generally generates ‘blurrier’ bitmap glyphs when the glyph are rendered in any of the anti-aliased modes. See also the note below. This flag is implied by |
| FT_LOAD_RENDER |
Call This flag is unset by |
| FT_LOAD_NO_BITMAP |
Ignore bitmap strikes when loading. Bitmap-only fonts ignore this flag.
|
| FT_LOAD_VERTICAL_LAYOUT |
Load the glyph for vertical text layout. In particular, the In case |
| FT_LOAD_FORCE_AUTOHINT |
Prefer the auto-hinter over the font's native hinter. See also the note below. |
| FT_LOAD_PEDANTIC |
Make the font driver perform pedantic verifications during glyph loading and hinting. This is mostly used to detect broken glyphs in fonts. By default, FreeType tries to handle broken fonts also. In particular, errors from the TrueType bytecode engine are not passed to the application if this flag is not set; this might result in partially hinted or distorted glyphs in case a glyph's bytecode is buggy. |
| FT_LOAD_NO_RECURSE |
Don't load composite glyphs recursively. Instead, the font driver fills the Don't use this flag for retrieving metrics information since some font drivers only return rudimentary data. This flag implies |
| FT_LOAD_IGNORE_TRANSFORM |
Ignore the transform matrix set by |
| FT_LOAD_MONOCHROME |
This flag is used with Note that this has no effect on the hinting algorithm used. You should rather use |
| FT_LOAD_LINEAR_DESIGN |
Keep |
| FT_LOAD_NO_AUTOHINT |
Disable the auto-hinter. See also the note below. |
| FT_LOAD_COLOR |
Load colored glyphs. There are slight differences depending on the font format. [Since 2.5] Load embedded color bitmap images. The resulting color bitmaps, if available, will have the [Since 2.10, experimental] If the glyph index contains an entry in the face's ‘COLR’ table with a ‘CPAL’ palette table (as defined in the OpenType specification), make |
| FT_LOAD_COMPUTE_METRICS |
[Since 2.6.1] Compute glyph metrics from the glyph data, without the use of bundled metrics tables (for example, the ‘hdmx’ table in TrueType fonts). This flag is mainly used by font validating or font editing applications, which need to ignore, verify, or edit those tables. Currently, this flag is only implemented for TrueType fonts. |
| FT_LOAD_BITMAP_METRICS_ONLY |
[Since 2.7.1] Request loading of the metrics and bitmap image information of a (possibly embedded) bitmap glyph without allocating or copying the bitmap image data itself. No effect if the target glyph is not a bitmap image. This flag unsets |
| FT_LOAD_CROP_BITMAP |
Ignored. Deprecated. |
| FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH |
Ignored. Deprecated. |
note
By default, hinting is enabled and the font's native hinter (see FT_FACE_FLAG_HINTER) is preferred over the auto-hinter. You can disable hinting by setting FT_LOAD_NO_HINTING or change the precedence by setting FT_LOAD_FORCE_AUTOHINT. You can also set FT_LOAD_NO_AUTOHINT in case you don't want the auto-hinter to be used at all.
See the description of FT_FACE_FLAG_TRICKY for a special exception (affecting only a handful of Asian fonts).
Besides deciding which hinter to use, you can also decide which hinting algorithm to use. See FT_LOAD_TARGET_XXX for details.
Note that the auto-hinter needs a valid Unicode cmap (either a native one or synthesized by FreeType) for producing correct results. If a font provides an incorrect mapping (for example, assigning the character code U+005A, LATIN CAPITAL LETTER Z, to a glyph depicting a mathematical integral sign), the auto-hinter might produce useless results.
FT_LOAD_TARGET_XXX¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_LOAD_TARGET_( x ) ( (FT_Int32)( (x) & 15 ) << 16 )
#define FT_LOAD_TARGET_NORMAL FT_LOAD_TARGET_( FT_RENDER_MODE_NORMAL )
#define FT_LOAD_TARGET_LIGHT FT_LOAD_TARGET_( FT_RENDER_MODE_LIGHT )
#define FT_LOAD_TARGET_MONO FT_LOAD_TARGET_( FT_RENDER_MODE_MONO )
#define FT_LOAD_TARGET_LCD FT_LOAD_TARGET_( FT_RENDER_MODE_LCD )
#define FT_LOAD_TARGET_LCD_V FT_LOAD_TARGET_( FT_RENDER_MODE_LCD_V )
A list of values to select a specific hinting algorithm for the hinter. You should OR one of these values to your load_flags when calling FT_Load_Glyph.
Note that a font's native hinters may ignore the hinting algorithm you have specified (e.g., the TrueType bytecode interpreter). You can set FT_LOAD_FORCE_AUTOHINT to ensure that the auto-hinter is used.
values
| FT_LOAD_TARGET_NORMAL |
The default hinting algorithm, optimized for standard gray-level rendering. For monochrome output, use |
| FT_LOAD_TARGET_LIGHT |
A lighter hinting algorithm for gray-level modes. Many generated glyphs are fuzzier but better resemble their original shape. This is achieved by snapping glyphs to the pixel grid only vertically (Y-axis), as is done by FreeType's new CFF engine or Microsoft's ClearType font renderer. This preserves inter-glyph spacing in horizontal text. The snapping is done either by the native font driver, if the driver itself and the font support it, or by the auto-hinter. Advance widths are rounded to integer values; however, using the If configuration option |
| FT_LOAD_TARGET_MONO |
Strong hinting algorithm that should only be used for monochrome output. The result is probably unpleasant if the glyph is rendered in non-monochrome modes. Note that for outline fonts only the TrueType font driver has proper monochrome hinting support, provided the TTFs contain hints for B/W rendering (which most fonts no longer provide). If these conditions are not met it is very likely that you get ugly results at smaller sizes. |
| FT_LOAD_TARGET_LCD |
A variant of |
| FT_LOAD_TARGET_LCD_V |
A variant of |
note
You should use only one of the FT_LOAD_TARGET_XXX values in your load_flags. They can't be ORed.
If FT_LOAD_RENDER is also set, the glyph is rendered in the corresponding mode (i.e., the mode that matches the used algorithm best). An exception is FT_LOAD_TARGET_MONO since it implies FT_LOAD_MONOCHROME.
You can use a hinting algorithm that doesn't correspond to the same rendering mode. As an example, it is possible to use the ‘light’ hinting algorithm and have the results rendered in horizontal LCD pixel mode, with code like
FT_Load_Glyph( face, glyph_index,
load_flags | FT_LOAD_TARGET_LIGHT );
FT_Render_Glyph( face->glyph, FT_RENDER_MODE_LCD );
In general, you should stick with one rendering mode. For example, switching between FT_LOAD_TARGET_NORMAL and FT_LOAD_TARGET_MONO enforces a lot of recomputation for TrueType fonts, which is slow. Another reason is caching: Selecting a different mode usually causes changes in both the outlines and the rasterized bitmaps; it is thus necessary to empty the cache after a mode switch to avoid false hits.
FT_SUBGLYPH_FLAG_XXX¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_SUBGLYPH_FLAG_ARGS_ARE_WORDS 1
#define FT_SUBGLYPH_FLAG_ARGS_ARE_XY_VALUES 2
#define FT_SUBGLYPH_FLAG_ROUND_XY_TO_GRID 4
#define FT_SUBGLYPH_FLAG_SCALE 8
#define FT_SUBGLYPH_FLAG_XY_SCALE 0x40
#define FT_SUBGLYPH_FLAG_2X2 0x80
#define FT_SUBGLYPH_FLAG_USE_MY_METRICS 0x200
A list of constants describing subglyphs. Please refer to the ‘glyf’ table description in the OpenType specification for the meaning of the various flags (which get synthesized for non-OpenType subglyphs).
https://docs.microsoft.com/en-us/typography/opentype/spec/glyf#composite-glyph-description
values
| FT_SUBGLYPH_FLAG_ARGS_ARE_WORDS | |
| FT_SUBGLYPH_FLAG_ARGS_ARE_XY_VALUES | |
| FT_SUBGLYPH_FLAG_ROUND_XY_TO_GRID | |
| FT_SUBGLYPH_FLAG_SCALE | |
| FT_SUBGLYPH_FLAG_XY_SCALE | |
| FT_SUBGLYPH_FLAG_2X2 | |
| FT_SUBGLYPH_FLAG_USE_MY_METRICS |
FT_FSTYPE_XXX¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_FSTYPE_INSTALLABLE_EMBEDDING 0x0000
#define FT_FSTYPE_RESTRICTED_LICENSE_EMBEDDING 0x0002
#define FT_FSTYPE_PREVIEW_AND_PRINT_EMBEDDING 0x0004
#define FT_FSTYPE_EDITABLE_EMBEDDING 0x0008
#define FT_FSTYPE_NO_SUBSETTING 0x0100
#define FT_FSTYPE_BITMAP_EMBEDDING_ONLY 0x0200
A list of bit flags used in the fsType field of the OS/2 table in a TrueType or OpenType font and the FSType entry in a PostScript font. These bit flags are returned by FT_Get_FSType_Flags; they inform client applications of embedding and subsetting restrictions associated with a font.
See https://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/FontPolicies.pdf for more details.
values
| FT_FSTYPE_INSTALLABLE_EMBEDDING |
Fonts with no fsType bit set may be embedded and permanently installed on the remote system by an application. |
| FT_FSTYPE_RESTRICTED_LICENSE_EMBEDDING |
Fonts that have only this bit set must not be modified, embedded or exchanged in any manner without first obtaining permission of the font software copyright owner. |
| FT_FSTYPE_PREVIEW_AND_PRINT_EMBEDDING |
The font may be embedded and temporarily loaded on the remote system. Documents containing Preview & Print fonts must be opened ‘read-only’; no edits can be applied to the document. |
| FT_FSTYPE_EDITABLE_EMBEDDING |
The font may be embedded but must only be installed temporarily on other systems. In contrast to Preview & Print fonts, documents containing editable fonts may be opened for reading, editing is permitted, and changes may be saved. |
| FT_FSTYPE_NO_SUBSETTING |
The font may not be subsetted prior to embedding. |
| FT_FSTYPE_BITMAP_EMBEDDING_ONLY |
Only bitmaps contained in the font may be embedded; no outline data may be embedded. If there are no bitmaps available in the font, then the font is unembeddable. |
note
The flags are ORed together, thus more than a single value can be returned.
While the fsType flags can indicate that a font may be embedded, a license with the font vendor may be separately required to use the font in this way.
FT_HAS_FAST_GLYPHS¶
Defined in FT_FREETYPE_H (freetype/freetype.h).
#define FT_HAS_FAST_GLYPHS( face ) 0
Deprecated.