| /***************************************************************************/ |
| /* */ |
| /* ftdriver.h */ |
| /* */ |
| /* FreeType API for controlling driver modules (specification only). */ |
| /* */ |
| /* Copyright 2017-2018 by */ |
| /* David Turner, Robert Wilhelm, and Werner Lemberg. */ |
| /* */ |
| /* This file is part of the FreeType project, and may only be used, */ |
| /* modified, and distributed under the terms of the FreeType project */ |
| /* license, LICENSE.TXT. By continuing to use, modify, or distribute */ |
| /* this file you indicate that you have read the license and */ |
| /* understand and accept it fully. */ |
| /* */ |
| /***************************************************************************/ |
| |
| |
| #ifndef FTDRIVER_H_ |
| #define FTDRIVER_H_ |
| |
| #include <ft2build.h> |
| #include FT_FREETYPE_H |
| #include FT_PARAMETER_TAGS_H |
| |
| #ifdef FREETYPE_H |
| #error "freetype.h of FreeType 1 has been loaded!" |
| #error "Please fix the directory search order for header files" |
| #error "so that freetype.h of FreeType 2 is found first." |
| #endif |
| |
| |
| FT_BEGIN_HEADER |
| |
| |
| /************************************************************************** |
| * |
| * @section: |
| * auto_hinter |
| * |
| * @title: |
| * The auto-hinter |
| * |
| * @abstract: |
| * Controlling the auto-hinting module. |
| * |
| * @description: |
| * While FreeType's auto-hinter doesn't expose API functions by itself, |
| * it is possible to control its behaviour with @FT_Property_Set and |
| * @FT_Property_Get. The following lists the available properties |
| * together with the necessary macros and structures. |
| * |
| * Note that the auto-hinter's module name is `autofitter' for |
| * historical reasons. |
| * |
| * Available properties are @increase-x-height, @no-stem-darkening |
| * (experimental), @darkening-parameters (experimental), @warping |
| * (experimental), @glyph-to-script-map (experimental), @fallback-script |
| * (experimental), and @default-script (experimental), as documented in |
| * the @properties section. |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @section: |
| * cff_driver |
| * |
| * @title: |
| * The CFF driver |
| * |
| * @abstract: |
| * Controlling the CFF driver module. |
| * |
| * @description: |
| * While FreeType's CFF driver doesn't expose API functions by itself, |
| * it is possible to control its behaviour with @FT_Property_Set and |
| * @FT_Property_Get. |
| * |
| * The CFF driver's module name is `cff'. |
| * |
| * Available properties are @hinting-engine, @no-stem-darkening, |
| * @darkening-parameters, and @random-seed, as documented in the |
| * @properties section. |
| * |
| * |
| * *Hinting* *and* *antialiasing* *principles* *of* *the* *new* *engine* |
| * |
| * The rasterizer is positioning horizontal features (e.g., ascender |
| * height & x-height, or crossbars) on the pixel grid and minimizing the |
| * amount of antialiasing applied to them, while placing vertical |
| * features (vertical stems) on the pixel grid without hinting, thus |
| * representing the stem position and weight accurately. Sometimes the |
| * vertical stems may be only partially black. In this context, |
| * `antialiasing' means that stems are not positioned exactly on pixel |
| * borders, causing a fuzzy appearance. |
| * |
| * There are two principles behind this approach. |
| * |
| * 1) No hinting in the horizontal direction: Unlike `superhinted' |
| * TrueType, which changes glyph widths to accommodate regular |
| * inter-glyph spacing, Adobe's approach is `faithful to the design' in |
| * representing both the glyph width and the inter-glyph spacing |
| * designed for the font. This makes the screen display as close as it |
| * can be to the result one would get with infinite resolution, while |
| * preserving what is considered the key characteristics of each glyph. |
| * Note that the distances between unhinted and grid-fitted positions at |
| * small sizes are comparable to kerning values and thus would be |
| * noticeable (and distracting) while reading if hinting were applied. |
| * |
| * One of the reasons to not hint horizontally is antialiasing for LCD |
| * screens: The pixel geometry of modern displays supplies three |
| * vertical subpixels as the eye moves horizontally across each visible |
| * pixel. On devices where we can be certain this characteristic is |
| * present a rasterizer can take advantage of the subpixels to add |
| * increments of weight. In Western writing systems this turns out to |
| * be the more critical direction anyway; the weights and spacing of |
| * vertical stems (see above) are central to Armenian, Cyrillic, Greek, |
| * and Latin type designs. Even when the rasterizer uses greyscale |
| * antialiasing instead of color (a necessary compromise when one |
| * doesn't know the screen characteristics), the unhinted vertical |
| * features preserve the design's weight and spacing much better than |
| * aliased type would. |
| * |
| * 2) Alignment in the vertical direction: Weights and spacing along the |
| * y~axis are less critical; what is much more important is the visual |
| * alignment of related features (like cap-height and x-height). The |
| * sense of alignment for these is enhanced by the sharpness of grid-fit |
| * edges, while the cruder vertical resolution (full pixels instead of |
| * 1/3 pixels) is less of a problem. |
| * |
| * On the technical side, horizontal alignment zones for ascender, |
| * x-height, and other important height values (traditionally called |
| * `blue zones') as defined in the font are positioned independently, |
| * each being rounded to the nearest pixel edge, taking care of |
| * overshoot suppression at small sizes, stem darkening, and scaling. |
| * |
| * Hstems (this is, hint values defined in the font to help align |
| * horizontal features) that fall within a blue zone are said to be |
| * `captured' and are aligned to that zone. Uncaptured stems are moved |
| * in one of four ways, top edge up or down, bottom edge up or down. |
| * Unless there are conflicting hstems, the smallest movement is taken |
| * to minimize distortion. |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @section: |
| * pcf_driver |
| * |
| * @title: |
| * The PCF driver |
| * |
| * @abstract: |
| * Controlling the PCF driver module. |
| * |
| * @description: |
| * While FreeType's PCF driver doesn't expose API functions by itself, |
| * it is possible to control its behaviour with @FT_Property_Set and |
| * @FT_Property_Get. Right now, there is a single property |
| * @no-long-family-names available if FreeType is compiled with |
| * PCF_CONFIG_OPTION_LONG_FAMILY_NAMES. |
| * |
| * The PCF driver's module name is `pcf'. |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @section: |
| * t1_cid_driver |
| * |
| * @title: |
| * The Type 1 and CID drivers |
| * |
| * @abstract: |
| * Controlling the Type~1 and CID driver modules. |
| * |
| * @description: |
| * It is possible to control the behaviour of FreeType's Type~1 and |
| * Type~1 CID drivers with @FT_Property_Set and @FT_Property_Get. |
| * |
| * Behind the scenes, both drivers use the Adobe CFF engine for hinting; |
| * however, the used properties must be specified separately. |
| * |
| * The Type~1 driver's module name is `type1'; the CID driver's module |
| * name is `t1cid'. |
| * |
| * Available properties are @hinting-engine, @no-stem-darkening, |
| * @darkening-parameters, and @random-seed, as documented in the |
| * @properties section. |
| * |
| * Please see the @cff_driver section for more details on the new |
| * hinting engine. |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @section: |
| * tt_driver |
| * |
| * @title: |
| * The TrueType driver |
| * |
| * @abstract: |
| * Controlling the TrueType driver module. |
| * |
| * @description: |
| * While FreeType's TrueType driver doesn't expose API functions by |
| * itself, it is possible to control its behaviour with @FT_Property_Set |
| * and @FT_Property_Get. The following lists the available properties |
| * together with the necessary macros and structures. |
| * |
| * The TrueType driver's module name is `truetype'. |
| * |
| * A single property @interpreter-version is available, as documented in |
| * the @properties section. |
| * |
| * We start with a list of definitions, kindly provided by Greg |
| * Hitchcock. |
| * |
| * _Bi-Level_ _Rendering_ |
| * |
| * Monochromatic rendering, exclusively used in the early days of |
| * TrueType by both Apple and Microsoft. Microsoft's GDI interface |
| * supported hinting of the right-side bearing point, such that the |
| * advance width could be non-linear. Most often this was done to |
| * achieve some level of glyph symmetry. To enable reasonable |
| * performance (e.g., not having to run hinting on all glyphs just to |
| * get the widths) there was a bit in the head table indicating if the |
| * side bearing was hinted, and additional tables, `hdmx' and `LTSH', to |
| * cache hinting widths across multiple sizes and device aspect ratios. |
| * |
| * _Font_ _Smoothing_ |
| * |
| * Microsoft's GDI implementation of anti-aliasing. Not traditional |
| * anti-aliasing as the outlines were hinted before the sampling. The |
| * widths matched the bi-level rendering. |
| * |
| * _ClearType_ _Rendering_ |
| * |
| * Technique that uses physical subpixels to improve rendering on LCD |
| * (and other) displays. Because of the higher resolution, many methods |
| * of improving symmetry in glyphs through hinting the right-side |
| * bearing were no longer necessary. This lead to what GDI calls |
| * `natural widths' ClearType, see |
| * http://www.beatstamm.com/typography/RTRCh4.htm#Sec21. Since hinting |
| * has extra resolution, most non-linearity went away, but it is still |
| * possible for hints to change the advance widths in this mode. |
| * |
| * _ClearType_ _Compatible_ _Widths_ |
| * |
| * One of the earliest challenges with ClearType was allowing the |
| * implementation in GDI to be selected without requiring all UI and |
| * documents to reflow. To address this, a compatible method of |
| * rendering ClearType was added where the font hints are executed once |
| * to determine the width in bi-level rendering, and then re-run in |
| * ClearType, with the difference in widths being absorbed in the font |
| * hints for ClearType (mostly in the white space of hints); see |
| * http://www.beatstamm.com/typography/RTRCh4.htm#Sec20. Somewhat by |
| * definition, compatible width ClearType allows for non-linear widths, |
| * but only when the bi-level version has non-linear widths. |
| * |
| * _ClearType_ _Subpixel_ _Positioning_ |
| * |
| * One of the nice benefits of ClearType is the ability to more crisply |
| * display fractional widths; unfortunately, the GDI model of integer |
| * bitmaps did not support this. However, the WPF and Direct Write |
| * frameworks do support fractional widths. DWrite calls this `natural |
| * mode', not to be confused with GDI's `natural widths'. Subpixel |
| * positioning, in the current implementation of Direct Write, |
| * unfortunately does not support hinted advance widths, see |
| * http://www.beatstamm.com/typography/RTRCh4.htm#Sec22. Note that the |
| * TrueType interpreter fully allows the advance width to be adjusted in |
| * this mode, just the DWrite client will ignore those changes. |
| * |
| * _ClearType_ _Backward_ _Compatibility_ |
| * |
| * This is a set of exceptions made in the TrueType interpreter to |
| * minimize hinting techniques that were problematic with the extra |
| * resolution of ClearType; see |
| * http://www.beatstamm.com/typography/RTRCh4.htm#Sec1 and |
| * https://www.microsoft.com/typography/cleartype/truetypecleartype.aspx. |
| * This technique is not to be confused with ClearType compatible |
| * widths. ClearType backward compatibility has no direct impact on |
| * changing advance widths, but there might be an indirect impact on |
| * disabling some deltas. This could be worked around in backward |
| * compatibility mode. |
| * |
| * _Native_ _ClearType_ _Mode_ |
| * |
| * (Not to be confused with `natural widths'.) This mode removes all |
| * the exceptions in the TrueType interpreter when running with |
| * ClearType. Any issues on widths would still apply, though. |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @section: |
| * properties |
| * |
| * @title: |
| * Driver properties |
| * |
| * @abstract: |
| * Controlling driver modules. |
| * |
| * @description: |
| * Driver modules can be controlled by setting and unsetting properties, |
| * using the functions @FT_Property_Set and @FT_Property_Get. This |
| * section documents the available properties, together with auxiliary |
| * macros and structures. |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @enum: |
| * FT_HINTING_XXX |
| * |
| * @description: |
| * A list of constants used for the @hinting-engine property to |
| * select the hinting engine for CFF, Type~1, and CID fonts. |
| * |
| * @values: |
| * FT_HINTING_FREETYPE :: |
| * Use the old FreeType hinting engine. |
| * |
| * FT_HINTING_ADOBE :: |
| * Use the hinting engine contributed by Adobe. |
| * |
| * @since: |
| * 2.9 |
| * |
| */ |
| #define FT_HINTING_FREETYPE 0 |
| #define FT_HINTING_ADOBE 1 |
| |
| /* these constants (introduced in 2.4.12) are deprecated */ |
| #define FT_CFF_HINTING_FREETYPE FT_HINTING_FREETYPE |
| #define FT_CFF_HINTING_ADOBE FT_HINTING_ADOBE |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * hinting-engine |
| * |
| * @description: |
| * Thanks to Adobe, which contributed a new hinting (and parsing) |
| * engine, an application can select between `freetype' and `adobe' if |
| * compiled with CFF_CONFIG_OPTION_OLD_ENGINE. If this configuration |
| * macro isn't defined, `hinting-engine' does nothing. |
| * |
| * The same holds for the Type~1 and CID modules if compiled with |
| * T1_CONFIG_OPTION_OLD_ENGINE. |
| * |
| * For the `cff' module, the default engine is `freetype' if |
| * CFF_CONFIG_OPTION_OLD_ENGINE is defined, and `adobe' otherwise. |
| * |
| * For both the `type1' and `t1cid' modules, the default engine is |
| * `freetype' if T1_CONFIG_OPTION_OLD_ENGINE is defined, and `adobe' |
| * otherwise. |
| * |
| * The following example code demonstrates how to select Adobe's hinting |
| * engine for the `cff' module (omitting the error handling). |
| * |
| * { |
| * FT_Library library; |
| * FT_UInt hinting_engine = FT_CFF_HINTING_ADOBE; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "cff", |
| * "hinting-engine", &hinting_engine ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * This property can be set via the `FREETYPE_PROPERTIES' environment |
| * variable (using values `adobe' or `freetype'). |
| * |
| * @since: |
| * 2.4.12 (for `cff' module) |
| * |
| * 2.9 (for `type1' and `t1cid' modules) |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * no-stem-darkening |
| * |
| * @description: |
| * All glyphs that pass through the auto-hinter will be emboldened |
| * unless this property is set to TRUE. The same is true for the CFF, |
| * Type~1, and CID font modules if the `Adobe' engine is selected (which |
| * is the default). |
| * |
| * Stem darkening emboldens glyphs at smaller sizes to make them more |
| * readable on common low-DPI screens when using linear alpha blending |
| * and gamma correction, see @FT_Render_Glyph. When not using linear |
| * alpha blending and gamma correction, glyphs will appear heavy and |
| * fuzzy! |
| * |
| * Gamma correction essentially lightens fonts since shades of grey are |
| * shifted to higher pixel values (=~higher brightness) to match the |
| * original intention to the reality of our screens. The side-effect is |
| * that glyphs `thin out'. Mac OS~X and Adobe's proprietary font |
| * rendering library implement a counter-measure: stem darkening at |
| * smaller sizes where shades of gray dominate. By emboldening a glyph |
| * slightly in relation to its pixel size, individual pixels get higher |
| * coverage of filled-in outlines and are therefore `blacker'. This |
| * counteracts the `thinning out' of glyphs, making text remain readable |
| * at smaller sizes. |
| * |
| * By default, the Adobe engines for CFF, Type~1, and CID fonts darken |
| * stems at smaller sizes, regardless of hinting, to enhance contrast. |
| * Setting this property, stem darkening gets switched off. |
| * |
| * For the auto-hinter, stem-darkening is experimental currently and |
| * thus switched off by default (this is, `no-stem-darkening' is set to |
| * TRUE by default). Total consistency with the CFF driver is not |
| * achieved right now because the emboldening method differs and glyphs |
| * must be scaled down on the Y-axis to keep outline points inside their |
| * precomputed blue zones. The smaller the size (especially 9ppem and |
| * down), the higher the loss of emboldening versus the CFF driver. |
| * |
| * Note that stem darkening is never applied if @FT_LOAD_NO_SCALE is |
| * set. |
| * |
| * { |
| * FT_Library library; |
| * FT_Bool no_stem_darkening = TRUE; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "cff", |
| * "no-stem-darkening", &no_stem_darkening ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * This property can be set via the `FREETYPE_PROPERTIES' environment |
| * variable (using values 1 and 0 for `on' and `off', respectively). |
| * It can also be set per face using @FT_Face_Properties with |
| * @FT_PARAM_TAG_STEM_DARKENING. |
| * |
| * @since: |
| * 2.4.12 (for `cff' module) |
| * |
| * 2.6.2 (for `autofitter' module) |
| * |
| * 2.9 (for `type1' and `t1cid' modules) |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * darkening-parameters |
| * |
| * @description: |
| * By default, the Adobe hinting engine, as used by the CFF, Type~1, and |
| * CID font drivers, darkens stems as follows (if the |
| * `no-stem-darkening' property isn't set): |
| * |
| * { |
| * stem width <= 0.5px: darkening amount = 0.4px |
| * stem width = 1px: darkening amount = 0.275px |
| * stem width = 1.667px: darkening amount = 0.275px |
| * stem width >= 2.333px: darkening amount = 0px |
| * } |
| * |
| * and piecewise linear in-between. At configuration time, these four |
| * control points can be set with the macro |
| * `CFF_CONFIG_OPTION_DARKENING_PARAMETERS'; the CFF, Type~1, and CID |
| * drivers share these values. At runtime, the control points can be |
| * changed using the `darkening-parameters' property, as the following |
| * example demonstrates for the Type~1 driver. |
| * |
| * { |
| * FT_Library library; |
| * FT_Int darken_params[8] = { 500, 300, // x1, y1 |
| * 1000, 200, // x2, y2 |
| * 1500, 100, // x3, y3 |
| * 2000, 0 }; // x4, y4 |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "type1", |
| * "darkening-parameters", darken_params ); |
| * } |
| * |
| * The x~values give the stem width, and the y~values the darkening |
| * amount. The unit is 1000th of pixels. All coordinate values must be |
| * positive; the x~values must be monotonically increasing; the |
| * y~values must be monotonically decreasing and smaller than or |
| * equal to 500 (corresponding to half a pixel); the slope of each |
| * linear piece must be shallower than -1 (e.g., -.4). |
| * |
| * The auto-hinter provides this property, too, as an experimental |
| * feature. See @no-stem-darkening for more. |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * This property can be set via the `FREETYPE_PROPERTIES' environment |
| * variable, using eight comma-separated integers without spaces. Here |
| * the above example, using `\' to break the line for readability. |
| * |
| * { |
| * FREETYPE_PROPERTIES=\ |
| * type1:darkening-parameters=500,300,1000,200,1500,100,2000,0 |
| * } |
| * |
| * @since: |
| * 2.5.1 (for `cff' module) |
| * |
| * 2.6.2 (for `autofitter' module) |
| * |
| * 2.9 (for `type1' and `t1cid' modules) |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * random-seed |
| * |
| * @description: |
| * By default, the seed value for the CFF `random' operator and the |
| * similar `0 28 callothersubr pop' command for the Type~1 and CID |
| * drivers is set to a random value. However, mainly for debugging |
| * purposes, it is often necessary to use a known value as a seed so |
| * that the pseudo-random number sequences generated by `random' are |
| * repeatable. |
| * |
| * The `random-seed' property does that. Its argument is a signed 32bit |
| * integer; if the value is zero or negative, the seed given by the |
| * `intitialRandomSeed' private DICT operator in a CFF file gets used |
| * (or a default value if there is no such operator). If the value is |
| * positive, use it instead of `initialRandomSeed', which is |
| * consequently ignored. |
| * |
| * @note: |
| * This property can be set via the `FREETYPE_PROPERTIES' environment |
| * variable. It can also be set per face using @FT_Face_Properties with |
| * @FT_PARAM_TAG_RANDOM_SEED. |
| * |
| * @since: |
| * 2.8 (for `cff' module) |
| * |
| * 2.9 (for `type1' and `t1cid' modules) |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * no-long-family-names |
| * |
| * @description: |
| * If PCF_CONFIG_OPTION_LONG_FAMILY_NAMES is active while compiling |
| * FreeType, the PCF driver constructs long family names. |
| * |
| * There are many PCF fonts just called `Fixed' which look completely |
| * different, and which have nothing to do with each other. When |
| * selecting `Fixed' in KDE or Gnome one gets results that appear rather |
| * random, the style changes often if one changes the size and one |
| * cannot select some fonts at all. The improve this situation, the PCF |
| * module prepends the foundry name (plus a space) to the family name. |
| * It also checks whether there are `wide' characters; all put together, |
| * family names like `Sony Fixed' or `Misc Fixed Wide' are constructed. |
| * |
| * If `no-long-family-names' is set, this feature gets switched off. |
| * |
| * { |
| * FT_Library library; |
| * FT_Bool no_long_family_names = TRUE; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "pcf", |
| * "no-long-family-names", |
| * &no_long_family_names ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * This property can be set via the `FREETYPE_PROPERTIES' environment |
| * variable (using values 1 and 0 for `on' and `off', respectively). |
| * |
| * @since: |
| * 2.8 |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @enum: |
| * TT_INTERPRETER_VERSION_XXX |
| * |
| * @description: |
| * A list of constants used for the @interpreter-version property to |
| * select the hinting engine for Truetype fonts. |
| * |
| * The numeric value in the constant names represents the version |
| * number as returned by the `GETINFO' bytecode instruction. |
| * |
| * @values: |
| * TT_INTERPRETER_VERSION_35 :: |
| * Version~35 corresponds to MS rasterizer v.1.7 as used e.g. in |
| * Windows~98; only grayscale and B/W rasterizing is supported. |
| * |
| * TT_INTERPRETER_VERSION_38 :: |
| * Version~38 corresponds to MS rasterizer v.1.9; it is roughly |
| * equivalent to the hinting provided by DirectWrite ClearType (as can |
| * be found, for example, in the Internet Explorer~9 running on |
| * Windows~7). It is used in FreeType to select the `Infinality' |
| * subpixel hinting code. The code may be removed in a future |
| * version. |
| * |
| * TT_INTERPRETER_VERSION_40 :: |
| * Version~40 corresponds to MS rasterizer v.2.1; it is roughly |
| * equivalent to the hinting provided by DirectWrite ClearType (as can |
| * be found, for example, in Microsoft's Edge Browser on Windows~10). |
| * It is used in FreeType to select the `minimal' subpixel hinting |
| * code, a stripped-down and higher performance version of the |
| * `Infinality' code. |
| * |
| * @note: |
| * This property controls the behaviour of the bytecode interpreter |
| * and thus how outlines get hinted. It does *not* control how glyph |
| * get rasterized! In particular, it does not control subpixel color |
| * filtering. |
| * |
| * If FreeType has not been compiled with the configuration option |
| * TT_CONFIG_OPTION_SUBPIXEL_HINTING, selecting version~38 or~40 causes |
| * an `FT_Err_Unimplemented_Feature' error. |
| * |
| * Depending on the graphics framework, Microsoft uses different |
| * bytecode and rendering engines. As a consequence, the version |
| * numbers returned by a call to the `GETINFO' bytecode instruction are |
| * more convoluted than desired. |
| * |
| * Here are two tables that try to shed some light on the possible |
| * values for the MS rasterizer engine, together with the additional |
| * features introduced by it. |
| * |
| * { |
| * GETINFO framework version feature |
| * ------------------------------------------------------------------- |
| * 3 GDI (Win 3.1), v1.0 16-bit, first version |
| * TrueImage |
| * 33 GDI (Win NT 3.1), v1.5 32-bit |
| * HP Laserjet |
| * 34 GDI (Win 95) v1.6 font smoothing, |
| * new SCANTYPE opcode |
| * 35 GDI (Win 98/2000) v1.7 (UN)SCALED_COMPONENT_OFFSET |
| * bits in composite glyphs |
| * 36 MGDI (Win CE 2) v1.6+ classic ClearType |
| * 37 GDI (XP and later), v1.8 ClearType |
| * GDI+ old (before Vista) |
| * 38 GDI+ old (Vista, Win 7), v1.9 subpixel ClearType, |
| * WPF Y-direction ClearType, |
| * additional error checking |
| * 39 DWrite (before Win 8) v2.0 subpixel ClearType flags |
| * in GETINFO opcode, |
| * bug fixes |
| * 40 GDI+ (after Win 7), v2.1 Y-direction ClearType flag |
| * DWrite (Win 8) in GETINFO opcode, |
| * Gray ClearType |
| * } |
| * |
| * The `version' field gives a rough orientation only, since some |
| * applications provided certain features much earlier (as an example, |
| * Microsoft Reader used subpixel and Y-direction ClearType already in |
| * Windows 2000). Similarly, updates to a given framework might include |
| * improved hinting support. |
| * |
| * { |
| * version sampling rendering comment |
| * x y x y |
| * -------------------------------------------------------------- |
| * v1.0 normal normal B/W B/W bi-level |
| * v1.6 high high gray gray grayscale |
| * v1.8 high normal color-filter B/W (GDI) ClearType |
| * v1.9 high high color-filter gray Color ClearType |
| * v2.1 high normal gray B/W Gray ClearType |
| * v2.1 high high gray gray Gray ClearType |
| * } |
| * |
| * Color and Gray ClearType are the two available variants of |
| * `Y-direction ClearType', meaning grayscale rasterization along the |
| * Y-direction; the name used in the TrueType specification for this |
| * feature is `symmetric smoothing'. `Classic ClearType' is the |
| * original algorithm used before introducing a modified version in |
| * Win~XP. Another name for v1.6's grayscale rendering is `font |
| * smoothing', and `Color ClearType' is sometimes also called `DWrite |
| * ClearType'. To differentiate between today's Color ClearType and the |
| * earlier ClearType variant with B/W rendering along the vertical axis, |
| * the latter is sometimes called `GDI ClearType'. |
| * |
| * `Normal' and `high' sampling describe the (virtual) resolution to |
| * access the rasterized outline after the hinting process. `Normal' |
| * means 1 sample per grid line (i.e., B/W). In the current Microsoft |
| * implementation, `high' means an extra virtual resolution of 16x16 (or |
| * 16x1) grid lines per pixel for bytecode instructions like `MIRP'. |
| * After hinting, these 16 grid lines are mapped to 6x5 (or 6x1) grid |
| * lines for color filtering if Color ClearType is activated. |
| * |
| * Note that `Gray ClearType' is essentially the same as v1.6's |
| * grayscale rendering. However, the GETINFO instruction handles it |
| * differently: v1.6 returns bit~12 (hinting for grayscale), while v2.1 |
| * returns bits~13 (hinting for ClearType), 18 (symmetrical smoothing), |
| * and~19 (Gray ClearType). Also, this mode respects bits 2 and~3 for |
| * the version~1 gasp table exclusively (like Color ClearType), while |
| * v1.6 only respects the values of version~0 (bits 0 and~1). |
| * |
| * Keep in mind that the features of the above interpreter versions |
| * might not map exactly to FreeType features or behavior because it is |
| * a fundamentally different library with different internals. |
| * |
| */ |
| #define TT_INTERPRETER_VERSION_35 35 |
| #define TT_INTERPRETER_VERSION_38 38 |
| #define TT_INTERPRETER_VERSION_40 40 |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * interpreter-version |
| * |
| * @description: |
| * Currently, three versions are available, two representing the |
| * bytecode interpreter with subpixel hinting support (old `Infinality' |
| * code and new stripped-down and higher performance `minimal' code) and |
| * one without, respectively. The default is subpixel support if |
| * TT_CONFIG_OPTION_SUBPIXEL_HINTING is defined, and no subpixel support |
| * otherwise (since it isn't available then). |
| * |
| * If subpixel hinting is on, many TrueType bytecode instructions behave |
| * differently compared to B/W or grayscale rendering (except if `native |
| * ClearType' is selected by the font). Microsoft's main idea is to |
| * render at a much increased horizontal resolution, then sampling down |
| * the created output to subpixel precision. However, many older fonts |
| * are not suited to this and must be specially taken care of by |
| * applying (hardcoded) tweaks in Microsoft's interpreter. |
| * |
| * Details on subpixel hinting and some of the necessary tweaks can be |
| * found in Greg Hitchcock's whitepaper at |
| * `https://www.microsoft.com/typography/cleartype/truetypecleartype.aspx'. |
| * Note that FreeType currently doesn't really `subpixel hint' (6x1, 6x2, |
| * or 6x5 supersampling) like discussed in the paper. Depending on the |
| * chosen interpreter, it simply ignores instructions on vertical stems |
| * to arrive at very similar results. |
| * |
| * The following example code demonstrates how to deactivate subpixel |
| * hinting (omitting the error handling). |
| * |
| * { |
| * FT_Library library; |
| * FT_Face face; |
| * FT_UInt interpreter_version = TT_INTERPRETER_VERSION_35; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "truetype", |
| * "interpreter-version", |
| * &interpreter_version ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * This property can be set via the `FREETYPE_PROPERTIES' environment |
| * variable (using values `35', `38', or `40'). |
| * |
| * @since: |
| * 2.5 |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * glyph-to-script-map |
| * |
| * @description: |
| * *Experimental* *only* |
| * |
| * The auto-hinter provides various script modules to hint glyphs. |
| * Examples of supported scripts are Latin or CJK. Before a glyph is |
| * auto-hinted, the Unicode character map of the font gets examined, and |
| * the script is then determined based on Unicode character ranges, see |
| * below. |
| * |
| * OpenType fonts, however, often provide much more glyphs than |
| * character codes (small caps, superscripts, ligatures, swashes, etc.), |
| * to be controlled by so-called `features'. Handling OpenType features |
| * can be quite complicated and thus needs a separate library on top of |
| * FreeType. |
| * |
| * The mapping between glyph indices and scripts (in the auto-hinter |
| * sense, see the @FT_AUTOHINTER_SCRIPT_XXX values) is stored as an |
| * array with `num_glyphs' elements, as found in the font's @FT_Face |
| * structure. The `glyph-to-script-map' property returns a pointer to |
| * this array, which can be modified as needed. Note that the |
| * modification should happen before the first glyph gets processed by |
| * the auto-hinter so that the global analysis of the font shapes |
| * actually uses the modified mapping. |
| * |
| * The following example code demonstrates how to access it (omitting |
| * the error handling). |
| * |
| * { |
| * FT_Library library; |
| * FT_Face face; |
| * FT_Prop_GlyphToScriptMap prop; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * FT_New_Face( library, "foo.ttf", 0, &face ); |
| * |
| * prop.face = face; |
| * |
| * FT_Property_Get( library, "autofitter", |
| * "glyph-to-script-map", &prop ); |
| * |
| * // adjust `prop.map' as needed right here |
| * |
| * FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT ); |
| * } |
| * |
| * @since: |
| * 2.4.11 |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @enum: |
| * FT_AUTOHINTER_SCRIPT_XXX |
| * |
| * @description: |
| * *Experimental* *only* |
| * |
| * A list of constants used for the @glyph-to-script-map property to |
| * specify the script submodule the auto-hinter should use for hinting a |
| * particular glyph. |
| * |
| * @values: |
| * FT_AUTOHINTER_SCRIPT_NONE :: |
| * Don't auto-hint this glyph. |
| * |
| * FT_AUTOHINTER_SCRIPT_LATIN :: |
| * Apply the latin auto-hinter. For the auto-hinter, `latin' is a |
| * very broad term, including Cyrillic and Greek also since characters |
| * from those scripts share the same design constraints. |
| * |
| * By default, characters from the following Unicode ranges are |
| * assigned to this submodule. |
| * |
| * { |
| * U+0020 - U+007F // Basic Latin (no control characters) |
| * U+00A0 - U+00FF // Latin-1 Supplement (no control characters) |
| * U+0100 - U+017F // Latin Extended-A |
| * U+0180 - U+024F // Latin Extended-B |
| * U+0250 - U+02AF // IPA Extensions |
| * U+02B0 - U+02FF // Spacing Modifier Letters |
| * U+0300 - U+036F // Combining Diacritical Marks |
| * U+0370 - U+03FF // Greek and Coptic |
| * U+0400 - U+04FF // Cyrillic |
| * U+0500 - U+052F // Cyrillic Supplement |
| * U+1D00 - U+1D7F // Phonetic Extensions |
| * U+1D80 - U+1DBF // Phonetic Extensions Supplement |
| * U+1DC0 - U+1DFF // Combining Diacritical Marks Supplement |
| * U+1E00 - U+1EFF // Latin Extended Additional |
| * U+1F00 - U+1FFF // Greek Extended |
| * U+2000 - U+206F // General Punctuation |
| * U+2070 - U+209F // Superscripts and Subscripts |
| * U+20A0 - U+20CF // Currency Symbols |
| * U+2150 - U+218F // Number Forms |
| * U+2460 - U+24FF // Enclosed Alphanumerics |
| * U+2C60 - U+2C7F // Latin Extended-C |
| * U+2DE0 - U+2DFF // Cyrillic Extended-A |
| * U+2E00 - U+2E7F // Supplemental Punctuation |
| * U+A640 - U+A69F // Cyrillic Extended-B |
| * U+A720 - U+A7FF // Latin Extended-D |
| * U+FB00 - U+FB06 // Alphab. Present. Forms (Latin Ligatures) |
| * U+1D400 - U+1D7FF // Mathematical Alphanumeric Symbols |
| * U+1F100 - U+1F1FF // Enclosed Alphanumeric Supplement |
| * } |
| * |
| * FT_AUTOHINTER_SCRIPT_CJK :: |
| * Apply the CJK auto-hinter, covering Chinese, Japanese, Korean, old |
| * Vietnamese, and some other scripts. |
| * |
| * By default, characters from the following Unicode ranges are |
| * assigned to this submodule. |
| * |
| * { |
| * U+1100 - U+11FF // Hangul Jamo |
| * U+2E80 - U+2EFF // CJK Radicals Supplement |
| * U+2F00 - U+2FDF // Kangxi Radicals |
| * U+2FF0 - U+2FFF // Ideographic Description Characters |
| * U+3000 - U+303F // CJK Symbols and Punctuation |
| * U+3040 - U+309F // Hiragana |
| * U+30A0 - U+30FF // Katakana |
| * U+3100 - U+312F // Bopomofo |
| * U+3130 - U+318F // Hangul Compatibility Jamo |
| * U+3190 - U+319F // Kanbun |
| * U+31A0 - U+31BF // Bopomofo Extended |
| * U+31C0 - U+31EF // CJK Strokes |
| * U+31F0 - U+31FF // Katakana Phonetic Extensions |
| * U+3200 - U+32FF // Enclosed CJK Letters and Months |
| * U+3300 - U+33FF // CJK Compatibility |
| * U+3400 - U+4DBF // CJK Unified Ideographs Extension A |
| * U+4DC0 - U+4DFF // Yijing Hexagram Symbols |
| * U+4E00 - U+9FFF // CJK Unified Ideographs |
| * U+A960 - U+A97F // Hangul Jamo Extended-A |
| * U+AC00 - U+D7AF // Hangul Syllables |
| * U+D7B0 - U+D7FF // Hangul Jamo Extended-B |
| * U+F900 - U+FAFF // CJK Compatibility Ideographs |
| * U+FE10 - U+FE1F // Vertical forms |
| * U+FE30 - U+FE4F // CJK Compatibility Forms |
| * U+FF00 - U+FFEF // Halfwidth and Fullwidth Forms |
| * U+1B000 - U+1B0FF // Kana Supplement |
| * U+1D300 - U+1D35F // Tai Xuan Hing Symbols |
| * U+1F200 - U+1F2FF // Enclosed Ideographic Supplement |
| * U+20000 - U+2A6DF // CJK Unified Ideographs Extension B |
| * U+2A700 - U+2B73F // CJK Unified Ideographs Extension C |
| * U+2B740 - U+2B81F // CJK Unified Ideographs Extension D |
| * U+2F800 - U+2FA1F // CJK Compatibility Ideographs Supplement |
| * } |
| * |
| * FT_AUTOHINTER_SCRIPT_INDIC :: |
| * Apply the indic auto-hinter, covering all major scripts from the |
| * Indian sub-continent and some other related scripts like Thai, Lao, |
| * or Tibetan. |
| * |
| * By default, characters from the following Unicode ranges are |
| * assigned to this submodule. |
| * |
| * { |
| * U+0900 - U+0DFF // Indic Range |
| * U+0F00 - U+0FFF // Tibetan |
| * U+1900 - U+194F // Limbu |
| * U+1B80 - U+1BBF // Sundanese |
| * U+A800 - U+A82F // Syloti Nagri |
| * U+ABC0 - U+ABFF // Meetei Mayek |
| * U+11800 - U+118DF // Sharada |
| * } |
| * |
| * Note that currently Indic support is rudimentary only, missing blue |
| * zone support. |
| * |
| * @since: |
| * 2.4.11 |
| * |
| */ |
| #define FT_AUTOHINTER_SCRIPT_NONE 0 |
| #define FT_AUTOHINTER_SCRIPT_LATIN 1 |
| #define FT_AUTOHINTER_SCRIPT_CJK 2 |
| #define FT_AUTOHINTER_SCRIPT_INDIC 3 |
| |
| |
| /************************************************************************** |
| * |
| * @struct: |
| * FT_Prop_GlyphToScriptMap |
| * |
| * @description: |
| * *Experimental* *only* |
| * |
| * The data exchange structure for the @glyph-to-script-map property. |
| * |
| * @since: |
| * 2.4.11 |
| * |
| */ |
| typedef struct FT_Prop_GlyphToScriptMap_ |
| { |
| FT_Face face; |
| FT_UShort* map; |
| |
| } FT_Prop_GlyphToScriptMap; |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * fallback-script |
| * |
| * @description: |
| * *Experimental* *only* |
| * |
| * If no auto-hinter script module can be assigned to a glyph, a |
| * fallback script gets assigned to it (see also the |
| * @glyph-to-script-map property). By default, this is |
| * @FT_AUTOHINTER_SCRIPT_CJK. Using the `fallback-script' property, |
| * this fallback value can be changed. |
| * |
| * { |
| * FT_Library library; |
| * FT_UInt fallback_script = FT_AUTOHINTER_SCRIPT_NONE; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "autofitter", |
| * "fallback-script", &fallback_script ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * It's important to use the right timing for changing this value: The |
| * creation of the glyph-to-script map that eventually uses the |
| * fallback script value gets triggered either by setting or reading a |
| * face-specific property like @glyph-to-script-map, or by auto-hinting |
| * any glyph from that face. In particular, if you have already created |
| * an @FT_Face structure but not loaded any glyph (using the |
| * auto-hinter), a change of the fallback script will affect this face. |
| * |
| * @since: |
| * 2.4.11 |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * default-script |
| * |
| * @description: |
| * *Experimental* *only* |
| * |
| * If FreeType gets compiled with FT_CONFIG_OPTION_USE_HARFBUZZ to make |
| * the HarfBuzz library access OpenType features for getting better |
| * glyph coverages, this property sets the (auto-fitter) script to be |
| * used for the default (OpenType) script data of a font's GSUB table. |
| * Features for the default script are intended for all scripts not |
| * explicitly handled in GSUB; an example is a `dlig' feature, |
| * containing the combination of the characters `T', `E', and `L' to |
| * form a `TEL' ligature. |
| * |
| * By default, this is @FT_AUTOHINTER_SCRIPT_LATIN. Using the |
| * `default-script' property, this default value can be changed. |
| * |
| * { |
| * FT_Library library; |
| * FT_UInt default_script = FT_AUTOHINTER_SCRIPT_NONE; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "autofitter", |
| * "default-script", &default_script ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * It's important to use the right timing for changing this value: The |
| * creation of the glyph-to-script map that eventually uses the |
| * default script value gets triggered either by setting or reading a |
| * face-specific property like @glyph-to-script-map, or by auto-hinting |
| * any glyph from that face. In particular, if you have already created |
| * an @FT_Face structure but not loaded any glyph (using the |
| * auto-hinter), a change of the default script will affect this face. |
| * |
| * @since: |
| * 2.5.3 |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * increase-x-height |
| * |
| * @description: |
| * For ppem values in the range 6~<= ppem <= `increase-x-height', round |
| * up the font's x~height much more often than normally. If the value |
| * is set to~0, which is the default, this feature is switched off. Use |
| * this property to improve the legibility of small font sizes if |
| * necessary. |
| * |
| * { |
| * FT_Library library; |
| * FT_Face face; |
| * FT_Prop_IncreaseXHeight prop; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * FT_New_Face( library, "foo.ttf", 0, &face ); |
| * FT_Set_Char_Size( face, 10 * 64, 0, 72, 0 ); |
| * |
| * prop.face = face; |
| * prop.limit = 14; |
| * |
| * FT_Property_Set( library, "autofitter", |
| * "increase-x-height", &prop ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * Set this value right after calling @FT_Set_Char_Size, but before |
| * loading any glyph (using the auto-hinter). |
| * |
| * @since: |
| * 2.4.11 |
| * |
| */ |
| |
| |
| /************************************************************************** |
| * |
| * @struct: |
| * FT_Prop_IncreaseXHeight |
| * |
| * @description: |
| * The data exchange structure for the @increase-x-height property. |
| * |
| */ |
| typedef struct FT_Prop_IncreaseXHeight_ |
| { |
| FT_Face face; |
| FT_UInt limit; |
| |
| } FT_Prop_IncreaseXHeight; |
| |
| |
| /************************************************************************** |
| * |
| * @property: |
| * warping |
| * |
| * @description: |
| * *Experimental* *only* |
| * |
| * If FreeType gets compiled with option AF_CONFIG_OPTION_USE_WARPER to |
| * activate the warp hinting code in the auto-hinter, this property |
| * switches warping on and off. |
| * |
| * Warping only works in `normal' auto-hinting mode replacing it. |
| * The idea of the code is to slightly scale and shift a glyph along |
| * the non-hinted dimension (which is usually the horizontal axis) so |
| * that as much of its segments are aligned (more or less) to the grid. |
| * To find out a glyph's optimal scaling and shifting value, various |
| * parameter combinations are tried and scored. |
| * |
| * By default, warping is off. The example below shows how to switch on |
| * warping (omitting the error handling). |
| * |
| * { |
| * FT_Library library; |
| * FT_Bool warping = 1; |
| * |
| * |
| * FT_Init_FreeType( &library ); |
| * |
| * FT_Property_Set( library, "autofitter", |
| * "warping", &warping ); |
| * } |
| * |
| * @note: |
| * This property can be used with @FT_Property_Get also. |
| * |
| * This property can be set via the `FREETYPE_PROPERTIES' environment |
| * variable (using values 1 and 0 for `on' and `off', respectively). |
| * |
| * The warping code can also change advance widths. Have a look at the |
| * `lsb_delta' and `rsb_delta' fields in the @FT_GlyphSlotRec structure |
| * for details on improving inter-glyph distances while rendering. |
| * |
| * Since warping is a global property of the auto-hinter it is best to |
| * change its value before rendering any face. Otherwise, you should |
| * reload all faces that get auto-hinted in `normal' hinting mode. |
| * |
| * @since: |
| * 2.6 |
| * |
| */ |
| |
| |
| /* */ |
| |
| |
| FT_END_HEADER |
| |
| |
| #endif /* FTDRIVER_H_ */ |
| |
| |
| /* END */ |
