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ftautoh.h
1/***************************************************************************/
2/* */
3/* ftautoh.h */
4/* */
5/* FreeType API for controlling the auto-hinter (specification only). */
6/* */
7/* Copyright 2012-2016 by */
8/* David Turner, Robert Wilhelm, and Werner Lemberg. */
9/* */
10/* This file is part of the FreeType project, and may only be used, */
11/* modified, and distributed under the terms of the FreeType project */
12/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
13/* this file you indicate that you have read the license and */
14/* understand and accept it fully. */
15/* */
16/***************************************************************************/
17
18
19#ifndef FTAUTOH_H_
20#define FTAUTOH_H_
21
22#include <ft2build.h>
23#include FT_FREETYPE_H
24
25#ifdef FREETYPE_H
26#error "freetype.h of FreeType 1 has been loaded!"
27#error "Please fix the directory search order for header files"
28#error "so that freetype.h of FreeType 2 is found first."
29#endif
30
31
32FT_BEGIN_HEADER
33
34
35 /**************************************************************************
36 *
37 * @section:
38 * auto_hinter
39 *
40 * @title:
41 * The auto-hinter
42 *
43 * @abstract:
44 * Controlling the auto-hinting module.
45 *
46 * @description:
47 * While FreeType's auto-hinter doesn't expose API functions by itself,
48 * it is possible to control its behaviour with @FT_Property_Set and
49 * @FT_Property_Get. The following lists the available properties
50 * together with the necessary macros and structures.
51 *
52 * Note that the auto-hinter's module name is `autofitter' for
53 * historical reasons.
54 *
55 */
56
57
58 /**************************************************************************
59 *
60 * @property:
61 * glyph-to-script-map
62 *
63 * @description:
64 * *Experimental* *only*
65 *
66 * The auto-hinter provides various script modules to hint glyphs.
67 * Examples of supported scripts are Latin or CJK. Before a glyph is
68 * auto-hinted, the Unicode character map of the font gets examined, and
69 * the script is then determined based on Unicode character ranges, see
70 * below.
71 *
72 * OpenType fonts, however, often provide much more glyphs than
73 * character codes (small caps, superscripts, ligatures, swashes, etc.),
74 * to be controlled by so-called `features'. Handling OpenType features
75 * can be quite complicated and thus needs a separate library on top of
76 * FreeType.
77 *
78 * The mapping between glyph indices and scripts (in the auto-hinter
79 * sense, see the @FT_AUTOHINTER_SCRIPT_XXX values) is stored as an
80 * array with `num_glyphs' elements, as found in the font's @FT_Face
81 * structure. The `glyph-to-script-map' property returns a pointer to
82 * this array, which can be modified as needed. Note that the
83 * modification should happen before the first glyph gets processed by
84 * the auto-hinter so that the global analysis of the font shapes
85 * actually uses the modified mapping.
86 *
87 * The following example code demonstrates how to access it (omitting
88 * the error handling).
89 *
90 * {
91 * FT_Library library;
92 * FT_Face face;
93 * FT_Prop_GlyphToScriptMap prop;
94 *
95 *
96 * FT_Init_FreeType( &library );
97 * FT_New_Face( library, "foo.ttf", 0, &face );
98 *
99 * prop.face = face;
100 *
101 * FT_Property_Get( library, "autofitter",
102 * "glyph-to-script-map", &prop );
103 *
104 * // adjust `prop.map' as needed right here
105 *
106 * FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT );
107 * }
108 *
109 */
110
111
112 /**************************************************************************
113 *
114 * @enum:
115 * FT_AUTOHINTER_SCRIPT_XXX
116 *
117 * @description:
118 * *Experimental* *only*
119 *
120 * A list of constants used for the @glyph-to-script-map property to
121 * specify the script submodule the auto-hinter should use for hinting a
122 * particular glyph.
123 *
124 * @values:
125 * FT_AUTOHINTER_SCRIPT_NONE ::
126 * Don't auto-hint this glyph.
127 *
128 * FT_AUTOHINTER_SCRIPT_LATIN ::
129 * Apply the latin auto-hinter. For the auto-hinter, `latin' is a
130 * very broad term, including Cyrillic and Greek also since characters
131 * from those scripts share the same design constraints.
132 *
133 * By default, characters from the following Unicode ranges are
134 * assigned to this submodule.
135 *
136 * {
137 * U+0020 - U+007F // Basic Latin (no control characters)
138 * U+00A0 - U+00FF // Latin-1 Supplement (no control characters)
139 * U+0100 - U+017F // Latin Extended-A
140 * U+0180 - U+024F // Latin Extended-B
141 * U+0250 - U+02AF // IPA Extensions
142 * U+02B0 - U+02FF // Spacing Modifier Letters
143 * U+0300 - U+036F // Combining Diacritical Marks
144 * U+0370 - U+03FF // Greek and Coptic
145 * U+0400 - U+04FF // Cyrillic
146 * U+0500 - U+052F // Cyrillic Supplement
147 * U+1D00 - U+1D7F // Phonetic Extensions
148 * U+1D80 - U+1DBF // Phonetic Extensions Supplement
149 * U+1DC0 - U+1DFF // Combining Diacritical Marks Supplement
150 * U+1E00 - U+1EFF // Latin Extended Additional
151 * U+1F00 - U+1FFF // Greek Extended
152 * U+2000 - U+206F // General Punctuation
153 * U+2070 - U+209F // Superscripts and Subscripts
154 * U+20A0 - U+20CF // Currency Symbols
155 * U+2150 - U+218F // Number Forms
156 * U+2460 - U+24FF // Enclosed Alphanumerics
157 * U+2C60 - U+2C7F // Latin Extended-C
158 * U+2DE0 - U+2DFF // Cyrillic Extended-A
159 * U+2E00 - U+2E7F // Supplemental Punctuation
160 * U+A640 - U+A69F // Cyrillic Extended-B
161 * U+A720 - U+A7FF // Latin Extended-D
162 * U+FB00 - U+FB06 // Alphab. Present. Forms (Latin Ligatures)
163 * U+1D400 - U+1D7FF // Mathematical Alphanumeric Symbols
164 * U+1F100 - U+1F1FF // Enclosed Alphanumeric Supplement
165 * }
166 *
167 * FT_AUTOHINTER_SCRIPT_CJK ::
168 * Apply the CJK auto-hinter, covering Chinese, Japanese, Korean, old
169 * Vietnamese, and some other scripts.
170 *
171 * By default, characters from the following Unicode ranges are
172 * assigned to this submodule.
173 *
174 * {
175 * U+1100 - U+11FF // Hangul Jamo
176 * U+2E80 - U+2EFF // CJK Radicals Supplement
177 * U+2F00 - U+2FDF // Kangxi Radicals
178 * U+2FF0 - U+2FFF // Ideographic Description Characters
179 * U+3000 - U+303F // CJK Symbols and Punctuation
180 * U+3040 - U+309F // Hiragana
181 * U+30A0 - U+30FF // Katakana
182 * U+3100 - U+312F // Bopomofo
183 * U+3130 - U+318F // Hangul Compatibility Jamo
184 * U+3190 - U+319F // Kanbun
185 * U+31A0 - U+31BF // Bopomofo Extended
186 * U+31C0 - U+31EF // CJK Strokes
187 * U+31F0 - U+31FF // Katakana Phonetic Extensions
188 * U+3200 - U+32FF // Enclosed CJK Letters and Months
189 * U+3300 - U+33FF // CJK Compatibility
190 * U+3400 - U+4DBF // CJK Unified Ideographs Extension A
191 * U+4DC0 - U+4DFF // Yijing Hexagram Symbols
192 * U+4E00 - U+9FFF // CJK Unified Ideographs
193 * U+A960 - U+A97F // Hangul Jamo Extended-A
194 * U+AC00 - U+D7AF // Hangul Syllables
195 * U+D7B0 - U+D7FF // Hangul Jamo Extended-B
196 * U+F900 - U+FAFF // CJK Compatibility Ideographs
197 * U+FE10 - U+FE1F // Vertical forms
198 * U+FE30 - U+FE4F // CJK Compatibility Forms
199 * U+FF00 - U+FFEF // Halfwidth and Fullwidth Forms
200 * U+1B000 - U+1B0FF // Kana Supplement
201 * U+1D300 - U+1D35F // Tai Xuan Hing Symbols
202 * U+1F200 - U+1F2FF // Enclosed Ideographic Supplement
203 * U+20000 - U+2A6DF // CJK Unified Ideographs Extension B
204 * U+2A700 - U+2B73F // CJK Unified Ideographs Extension C
205 * U+2B740 - U+2B81F // CJK Unified Ideographs Extension D
206 * U+2F800 - U+2FA1F // CJK Compatibility Ideographs Supplement
207 * }
208 *
209 * FT_AUTOHINTER_SCRIPT_INDIC ::
210 * Apply the indic auto-hinter, covering all major scripts from the
211 * Indian sub-continent and some other related scripts like Thai, Lao,
212 * or Tibetan.
213 *
214 * By default, characters from the following Unicode ranges are
215 * assigned to this submodule.
216 *
217 * {
218 * U+0900 - U+0DFF // Indic Range
219 * U+0F00 - U+0FFF // Tibetan
220 * U+1900 - U+194F // Limbu
221 * U+1B80 - U+1BBF // Sundanese
222 * U+1C80 - U+1CDF // Meetei Mayak
223 * U+A800 - U+A82F // Syloti Nagri
224 * U+11800 - U+118DF // Sharada
225 * }
226 *
227 * Note that currently Indic support is rudimentary only, missing blue
228 * zone support.
229 *
230 */
231#define FT_AUTOHINTER_SCRIPT_NONE 0
232#define FT_AUTOHINTER_SCRIPT_LATIN 1
233#define FT_AUTOHINTER_SCRIPT_CJK 2
234#define FT_AUTOHINTER_SCRIPT_INDIC 3
235
236
237 /**************************************************************************
238 *
239 * @struct:
240 * FT_Prop_GlyphToScriptMap
241 *
242 * @description:
243 * *Experimental* *only*
244 *
245 * The data exchange structure for the @glyph-to-script-map property.
246 *
247 */
248 typedef struct FT_Prop_GlyphToScriptMap_
249 {
250 FT_Face face;
251 FT_UShort* map;
252
253 } FT_Prop_GlyphToScriptMap;
254
255
256 /**************************************************************************
257 *
258 * @property:
259 * fallback-script
260 *
261 * @description:
262 * *Experimental* *only*
263 *
264 * If no auto-hinter script module can be assigned to a glyph, a
265 * fallback script gets assigned to it (see also the
266 * @glyph-to-script-map property). By default, this is
267 * @FT_AUTOHINTER_SCRIPT_CJK. Using the `fallback-script' property,
268 * this fallback value can be changed.
269 *
270 * {
271 * FT_Library library;
272 * FT_UInt fallback_script = FT_AUTOHINTER_SCRIPT_NONE;
273 *
274 *
275 * FT_Init_FreeType( &library );
276 *
277 * FT_Property_Set( library, "autofitter",
278 * "fallback-script", &fallback_script );
279 * }
280 *
281 * @note:
282 * This property can be used with @FT_Property_Get also.
283 *
284 * It's important to use the right timing for changing this value: The
285 * creation of the glyph-to-script map that eventually uses the
286 * fallback script value gets triggered either by setting or reading a
287 * face-specific property like @glyph-to-script-map, or by auto-hinting
288 * any glyph from that face. In particular, if you have already created
289 * an @FT_Face structure but not loaded any glyph (using the
290 * auto-hinter), a change of the fallback script will affect this face.
291 *
292 */
293
294
295 /**************************************************************************
296 *
297 * @property:
298 * default-script
299 *
300 * @description:
301 * *Experimental* *only*
302 *
303 * If FreeType gets compiled with FT_CONFIG_OPTION_USE_HARFBUZZ to make
304 * the HarfBuzz library access OpenType features for getting better
305 * glyph coverages, this property sets the (auto-fitter) script to be
306 * used for the default (OpenType) script data of a font's GSUB table.
307 * Features for the default script are intended for all scripts not
308 * explicitly handled in GSUB; an example is a `dlig' feature,
309 * containing the combination of the characters `T', `E', and `L' to
310 * form a `TEL' ligature.
311 *
312 * By default, this is @FT_AUTOHINTER_SCRIPT_LATIN. Using the
313 * `default-script' property, this default value can be changed.
314 *
315 * {
316 * FT_Library library;
317 * FT_UInt default_script = FT_AUTOHINTER_SCRIPT_NONE;
318 *
319 *
320 * FT_Init_FreeType( &library );
321 *
322 * FT_Property_Set( library, "autofitter",
323 * "default-script", &default_script );
324 * }
325 *
326 * @note:
327 * This property can be used with @FT_Property_Get also.
328 *
329 * It's important to use the right timing for changing this value: The
330 * creation of the glyph-to-script map that eventually uses the
331 * default script value gets triggered either by setting or reading a
332 * face-specific property like @glyph-to-script-map, or by auto-hinting
333 * any glyph from that face. In particular, if you have already created
334 * an @FT_Face structure but not loaded any glyph (using the
335 * auto-hinter), a change of the default script will affect this face.
336 *
337 */
338
339
340 /**************************************************************************
341 *
342 * @property:
343 * increase-x-height
344 *
345 * @description:
346 * For ppem values in the range 6~<= ppem <= `increase-x-height', round
347 * up the font's x~height much more often than normally. If the value
348 * is set to~0, which is the default, this feature is switched off. Use
349 * this property to improve the legibility of small font sizes if
350 * necessary.
351 *
352 * {
353 * FT_Library library;
354 * FT_Face face;
355 * FT_Prop_IncreaseXHeight prop;
356 *
357 *
358 * FT_Init_FreeType( &library );
359 * FT_New_Face( library, "foo.ttf", 0, &face );
360 * FT_Set_Char_Size( face, 10 * 64, 0, 72, 0 );
361 *
362 * prop.face = face;
363 * prop.limit = 14;
364 *
365 * FT_Property_Set( library, "autofitter",
366 * "increase-x-height", &prop );
367 * }
368 *
369 * @note:
370 * This property can be used with @FT_Property_Get also.
371 *
372 * Set this value right after calling @FT_Set_Char_Size, but before
373 * loading any glyph (using the auto-hinter).
374 *
375 */
376
377
378 /**************************************************************************
379 *
380 * @struct:
381 * FT_Prop_IncreaseXHeight
382 *
383 * @description:
384 * The data exchange structure for the @increase-x-height property.
385 *
386 */
387 typedef struct FT_Prop_IncreaseXHeight_
388 {
389 FT_Face face;
390 FT_UInt limit;
391
392 } FT_Prop_IncreaseXHeight;
393
394
395 /**************************************************************************
396 *
397 * @property:
398 * warping
399 *
400 * @description:
401 * *Experimental* *only*
402 *
403 * If FreeType gets compiled with option AF_CONFIG_OPTION_USE_WARPER to
404 * activate the warp hinting code in the auto-hinter, this property
405 * switches warping on and off.
406 *
407 * Warping only works in `light' auto-hinting mode. The idea of the
408 * code is to slightly scale and shift a glyph along the non-hinted
409 * dimension (which is usually the horizontal axis) so that as much of
410 * its segments are aligned (more or less) to the grid. To find out a
411 * glyph's optimal scaling and shifting value, various parameter
412 * combinations are tried and scored.
413 *
414 * By default, warping is off. The example below shows how to switch on
415 * warping (omitting the error handling).
416 *
417 * {
418 * FT_Library library;
419 * FT_Bool warping = 1;
420 *
421 *
422 * FT_Init_FreeType( &library );
423 *
424 * FT_Property_Set( library, "autofitter",
425 * "warping", &warping );
426 * }
427 *
428 * @note:
429 * This property can be used with @FT_Property_Get also.
430 *
431 * The warping code can also change advance widths. Have a look at the
432 * `lsb_delta' and `rsb_delta' fields in the @FT_GlyphSlotRec structure
433 * for details on improving inter-glyph distances while rendering.
434 *
435 * Since warping is a global property of the auto-hinter it is best to
436 * change its value before rendering any face. Otherwise, you should
437 * reload all faces that get auto-hinted in `light' hinting mode.
438 *
439 */
440
441
442 /**************************************************************************
443 *
444 * @property:
445 * no-stem-darkening[autofit]
446 *
447 * @description:
448 * *Experimental* *only,* *requires* *linear* *alpha* *blending* *and*
449 * *gamma* *correction*
450 *
451 * Stem darkening emboldens glyphs at smaller sizes to make them more
452 * readable on common low-DPI screens when using linear alpha blending
453 * and gamma correction, see @FT_Render_Glyph. When not using linear
454 * alpha blending and gamma correction, glyphs will appear heavy and
455 * fuzzy!
456 *
457 * Gamma correction essentially lightens fonts since shades of grey are
458 * shifted to higher pixel values (=~higher brightness) to match the
459 * original intention to the reality of our screens. The side-effect is
460 * that glyphs `thin out'. Mac OS~X and Adobe's proprietary font
461 * rendering library implement a counter-measure: stem darkening at
462 * smaller sizes where shades of gray dominate. By emboldening a glyph
463 * slightly in relation to its pixel size, individual pixels get higher
464 * coverage of filled-in outlines and are therefore `blacker'. This
465 * counteracts the `thinning out' of glyphs, making text remain readable
466 * at smaller sizes. All glyphs that pass through the auto-hinter will
467 * be emboldened unless this property is set to TRUE.
468 *
469 * See the description of the CFF driver for algorithmic details. Total
470 * consistency with the CFF driver is currently not achieved because the
471 * emboldening method differs and glyphs must be scaled down on the
472 * Y-axis to keep outline points inside their precomputed blue zones.
473 * The smaller the size (especially 9ppem and down), the higher the loss
474 * of emboldening versus the CFF driver.
475 *
476 */
477
478
479 /**************************************************************************
480 *
481 * @property:
482 * darkening-parameters[autofit]
483 *
484 * @description:
485 * *Experimental* *only*
486 *
487 * See the description of the CFF driver for details. This
488 * implementation appropriates the
489 * CFF_CONFIG_OPTION_DARKENING_PARAMETER_* #defines for consistency.
490 * Note the differences described in @no-stem-darkening[autofit].
491 *
492 */
493
494
495 /* */
496
497
498FT_END_HEADER
499
500#endif /* FTAUTOH_H_ */
501
502
503/* END */
FT_FaceRec_
Definition freetype.h:1034
FT_Prop_GlyphToScriptMap_
Definition ftautoh.h:249
FT_Prop_IncreaseXHeight_
Definition ftautoh.h:388
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