+++ /dev/null
-/***************************************************************************/
-/* */
-/* ftcffdrv.h */
-/* */
-/* FreeType API for controlling the CFF driver (specification only). */
-/* */
-/* Copyright 2013-2017 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 FTCFFDRV_H_
-#define FTCFFDRV_H_
-
-#include <ft2build.h>
-#include FT_FREETYPE_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:
- * 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 list below gives the available properties
- * together with the necessary macros and structures.
- *
- * The CFF driver's module name is `cff'.
- *
- * *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 sub-pixels 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 sub-pixels 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.
- *
- * @order:
- * hinting-engine[cff]
- * no-stem-darkening[cff]
- * darkening-parameters[cff]
- * random-seed
- *
- */
-
-
- /**************************************************************************
- *
- * @property:
- * hinting-engine[cff]
- *
- * @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 default engine is `freetype' if CFF_CONFIG_OPTION_OLD_ENGINE is
- * defined, and `adobe' otherwise.
- *
- * The following example code demonstrates how to select Adobe's hinting
- * engine (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').
- */
-
-
- /**************************************************************************
- *
- * @enum:
- * FT_CFF_HINTING_XXX
- *
- * @description:
- * A list of constants used for the @hinting-engine[cff] property to
- * select the hinting engine for CFF fonts.
- *
- * @values:
- * FT_CFF_HINTING_FREETYPE ::
- * Use the old FreeType hinting engine.
- *
- * FT_CFF_HINTING_ADOBE ::
- * Use the hinting engine contributed by Adobe.
- *
- */
-#define FT_CFF_HINTING_FREETYPE 0
-#define FT_CFF_HINTING_ADOBE 1
-
-
- /**************************************************************************
- *
- * @property:
- * no-stem-darkening[cff]
- *
- * @description:
- * By default, the Adobe CFF engine darkens stems at smaller sizes,
- * regardless of hinting, to enhance contrast. This feature requires
- * a rendering system with proper gamma correction. Setting this
- * property, stem darkening gets switched off.
- *
- * 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.
- *
- */
-
-
- /**************************************************************************
- *
- * @property:
- * darkening-parameters[cff]
- *
- * @description:
- * By default, the Adobe CFF engine 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'. At runtime, the control
- * points can be changed using the `darkening-parameters' property, as
- * the following example demonstrates.
- *
- * {
- * 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, "cff",
- * "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).
- *
- * @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=\
- * cff:darkening-parameters=500,300,1000,200,1500,100,2000,0
- * }
- */
-
-
- /**************************************************************************
- *
- * @property:
- * random-seed
- *
- * @description:
- * By default, the seed value for the CFF `random' operator 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.
- *
- */
-
-
- /**************************************************************************
- *
- * @constant:
- * FT_PARAM_TAG_RANDOM_SEED
- *
- * @description:
- * An @FT_Parameter tag to be used with @FT_Face_Properties. The
- * corresponding 32bit signed integer argument overrides the CFF
- * module's random seed value with a face-specific one; see
- * @random-seed.
- *
- */
-#define FT_PARAM_TAG_RANDOM_SEED \
- FT_MAKE_TAG( 's', 'e', 'e', 'd' )
-
-
- /* */
-
-
-FT_END_HEADER
-
-
-#endif /* FTCFFDRV_H_ */
-
-
-/* END */
projects / reactos.git / blobdiff