cf2font.c revision 727dee178a392d20eb050d0c446f2fcc29058fa1 
1/***************************************************************************/
2/*                                                                         */
3/*  cf2font.c                                                              */
4/*                                                                         */
5/*    Adobe's code for font instances (body).                              */
6/*                                                                         */
7/*  Copyright 2007-2013 Adobe Systems Incorporated.                        */
8/*                                                                         */
9/*  This software, and all works of authorship, whether in source or       */
10/*  object code form as indicated by the copyright notice(s) included      */
11/*  herein (collectively, the "Work") is made available, and may only be   */
12/*  used, modified, and distributed under the FreeType Project License,    */
13/*  LICENSE.TXT.  Additionally, subject to the terms and conditions of the */
14/*  FreeType Project License, each contributor to the Work hereby grants   */
15/*  to any individual or legal entity exercising permissions granted by    */
16/*  the FreeType Project License and this section (hereafter, "You" or     */
17/*  "Your") a perpetual, worldwide, non-exclusive, no-charge,              */
18/*  royalty-free, irrevocable (except as stated in this section) patent    */
19/*  license to make, have made, use, offer to sell, sell, import, and      */
20/*  otherwise transfer the Work, where such license applies only to those  */
21/*  patent claims licensable by such contributor that are necessarily      */
22/*  infringed by their contribution(s) alone or by combination of their    */
23/*  contribution(s) with the Work to which such contribution(s) was        */
24/*  submitted.  If You institute patent litigation against any entity      */
25/*  (including a cross-claim or counterclaim in a lawsuit) alleging that   */
26/*  the Work or a contribution incorporated within the Work constitutes    */
27/*  direct or contributory patent infringement, then any patent licenses   */
28/*  granted to You under this License for that Work shall terminate as of  */
29/*  the date such litigation is filed.                                     */
30/*                                                                         */
31/*  By using, modifying, or distributing the Work you indicate that you    */
32/*  have read and understood the terms and conditions of the               */
33/*  FreeType Project License as well as those provided in this section,    */
34/*  and you accept them fully.                                             */
35/*                                                                         */
36/***************************************************************************/
37
38
39#include "cf2ft.h"
40
41#include "cf2glue.h"
42#include "cf2font.h"
43#include "cf2error.h"
44#include "cf2intrp.h"
45
46
47  /* Compute a stem darkening amount in character space. */
48  static void
49  cf2_computeDarkening( CF2_Fixed   emRatio,
50                        CF2_Fixed   ppem,
51                        CF2_Fixed   stemWidth,
52                        CF2_Fixed*  darkenAmount,
53                        CF2_Fixed   boldenAmount,
54                        FT_Bool     stemDarkened )
55  {
56    /* Internal calculations are done in units per thousand for */
57    /* convenience.                                             */
58    CF2_Fixed  stemWidthPer1000, scaledStem;
59
60
61    *darkenAmount = 0;
62
63    if ( boldenAmount == 0 && !stemDarkened )
64      return;
65
66    /* protect against range problems and divide by zero */
67    if ( emRatio < cf2_floatToFixed( .01 ) )
68      return;
69
70    if ( stemDarkened )
71    {
72      /* convert from true character space to 1000 unit character space; */
73      /* add synthetic emboldening effect                                */
74
75      /* we have to assure that the computation of `scaledStem' */
76      /* and `stemWidthPer1000' don't overflow                  */
77
78      stemWidthPer1000 = FT_MulFix( stemWidth + boldenAmount, emRatio );
79
80      if ( emRatio > CF2_FIXED_ONE                          &&
81           stemWidthPer1000 <= ( stemWidth + boldenAmount ) )
82      {
83        stemWidthPer1000 = 0;                      /* to pacify compiler */
84        scaledStem       = cf2_intToFixed( 2333 );
85      }
86      else
87      {
88        scaledStem = FT_MulFix( stemWidthPer1000, ppem );
89
90        if ( ppem > CF2_FIXED_ONE           &&
91             scaledStem <= stemWidthPer1000 )
92          scaledStem = cf2_intToFixed( 2333 );
93      }
94
95      /*
96       * Total darkening amount is computed in 1000 unit character space
97       * using the modified 5 part curve as Avalon rasterizer.
98       * The darkening amount is smaller for thicker stems.
99       * It becomes zero when the stem is thicker than 2.333 pixels.
100       *
101       * In Avalon rasterizer,
102       *
103       *   darkenAmount = 0.5 pixels   if scaledStem <= 0.5 pixels,
104       *   darkenAmount = 0.333 pixels if 1 <= scaledStem <= 1.667 pixels,
105       *   darkenAmount = 0 pixel      if scaledStem >= 2.333 pixels,
106       *
107       * and piecewise linear in-between.
108       *
109       */
110      if ( scaledStem < cf2_intToFixed( 500 ) )
111        *darkenAmount = FT_DivFix( cf2_intToFixed( 400 ), ppem );
112
113      else if ( scaledStem < cf2_intToFixed( 1000 ) )
114        *darkenAmount = FT_DivFix( cf2_intToFixed( 525 ), ppem ) -
115                          FT_MulFix( stemWidthPer1000,
116                                     cf2_floatToFixed( .25 ) );
117
118      else if ( scaledStem < cf2_intToFixed( 1667 ) )
119        *darkenAmount = FT_DivFix( cf2_intToFixed( 275 ), ppem );
120
121      else if ( scaledStem < cf2_intToFixed( 2333 ) )
122        *darkenAmount = FT_DivFix( cf2_intToFixed( 963 ), ppem ) -
123                          FT_MulFix( stemWidthPer1000,
124                                     cf2_floatToFixed( .413 ) );
125
126      /* use half the amount on each side and convert back to true */
127      /* character space                                           */
128      *darkenAmount = FT_DivFix( *darkenAmount, 2 * emRatio );
129    }
130
131    /* add synthetic emboldening effect in character space */
132    *darkenAmount += boldenAmount / 2;
133  }
134
135
136  /* set up values for the current FontDict and matrix */
137
138  /* caller's transform is adjusted for subpixel positioning */
139  static void
140  cf2_font_setup( CF2_Font           font,
141                  const CF2_Matrix*  transform )
142  {
143    /* pointer to parsed font object */
144    CFF_Decoder*  decoder = font->decoder;
145
146    FT_Bool  needExtraSetup;
147
148    /* character space units */
149    CF2_Fixed  boldenX = font->syntheticEmboldeningAmountX;
150    CF2_Fixed  boldenY = font->syntheticEmboldeningAmountY;
151
152    CF2_Fixed  ppem;
153
154
155    /* clear previous error */
156    font->error = FT_Err_Ok;
157
158    /* if a CID fontDict has changed, we need to recompute some cached */
159    /* data                                                            */
160    needExtraSetup = font->lastSubfont != cf2_getSubfont( decoder );
161
162    /* if ppem has changed, we need to recompute some cached data         */
163    /* note: because of CID font matrix concatenation, ppem and transform */
164    /*       do not necessarily track.                                    */
165    ppem = cf2_getPpemY( decoder );
166    if ( font->ppem != ppem )
167    {
168      font->ppem     = ppem;
169      needExtraSetup = TRUE;
170    }
171
172    /* copy hinted flag on each call */
173    font->hinted = font->renderingFlags & CF2_FlagsHinted;
174
175    /* determine if transform has changed;       */
176    /* include Fontmatrix but ignore translation */
177    if ( ft_memcmp( transform,
178                    &font->currentTransform,
179                    4 * sizeof ( CF2_Fixed ) ) != 0 )
180    {
181      /* save `key' information for `cache of one' matrix data; */
182      /* save client transform, without the translation         */
183      font->currentTransform    = *transform;
184      font->currentTransform.tx =
185      font->currentTransform.ty = cf2_intToFixed( 0 );
186
187      /* TODO: FreeType transform is simple scalar; for now, use identity */
188      /*       for outer                                                  */
189      font->innerTransform   = *transform;
190      font->outerTransform.a =
191      font->outerTransform.d = cf2_intToFixed( 1 );
192      font->outerTransform.b =
193      font->outerTransform.c = cf2_intToFixed( 0 );
194
195      needExtraSetup = TRUE;
196    }
197
198    /*
199     * font->darkened is set to true if there is a stem darkening request or
200     * the font is synthetic emboldened.
201     * font->darkened controls whether to adjust blue zones, winding order,
202     * and hinting.
203     *
204     */
205    if ( font->stemDarkened != ( font->renderingFlags & CF2_FlagsDarkened ) )
206    {
207      font->stemDarkened = font->renderingFlags & CF2_FlagsDarkened;
208
209      /* blue zones depend on darkened flag */
210      needExtraSetup = TRUE;
211    }
212
213    /* recompute variables that are dependent on transform or FontDict or */
214    /* darken flag                                                        */
215    if ( needExtraSetup )
216    {
217      /* StdVW is found in the private dictionary;                       */
218      /* recompute darkening amounts whenever private dictionary or      */
219      /* transform change                                                */
220      /* Note: a rendering flag turns darkening on or off, so we want to */
221      /*       store the `on' amounts;                                   */
222      /*       darkening amount is computed in character space           */
223      /* TODO: testing size-dependent darkening here;                    */
224      /*       what to do for rotations?                                 */
225
226      CF2_Fixed  emRatio;
227      CF2_Fixed  stdHW;
228      CF2_Int    unitsPerEm = font->unitsPerEm;
229
230
231      if ( unitsPerEm == 0 )
232        unitsPerEm = 1000;
233
234      ppem = FT_MAX( cf2_intToFixed( 4 ),
235                     font->ppem ); /* use minimum ppem of 4 */
236
237#if 0
238      /* since vstem is measured in the x-direction, we use the `a' member */
239      /* of the fontMatrix                                                 */
240      emRatio = cf2_fixedFracMul( cf2_intToFixed( 1000 ), fontMatrix->a );
241#endif
242
243      /* Freetype does not preserve the fontMatrix when parsing; use */
244      /* unitsPerEm instead.                                         */
245      /* TODO: check precision of this                               */
246      emRatio     = cf2_intToFixed( 1000 ) / unitsPerEm;
247      font->stdVW = cf2_getStdVW( decoder );
248
249      if ( font->stdVW <= 0 )
250        font->stdVW = FT_DivFix( cf2_intToFixed( 75 ), emRatio );
251
252      if ( boldenX > 0 )
253      {
254        /* Ensure that boldenX is at least 1 pixel for synthetic bold font */
255        /* (similar to what Avalon does)                                   */
256        boldenX = FT_MAX( boldenX,
257                          FT_DivFix( cf2_intToFixed( unitsPerEm ), ppem ) );
258
259        /* Synthetic emboldening adds at least 1 pixel to darkenX, while */
260        /* stem darkening adds at most half pixel.  Since the purpose of */
261        /* stem darkening (readability at small sizes) is met with       */
262        /* synthetic emboldening, no need to add stem darkening for a    */
263        /* synthetic bold font.                                          */
264        cf2_computeDarkening( emRatio,
265                              ppem,
266                              font->stdVW,
267                              &font->darkenX,
268                              boldenX,
269                              FALSE );
270      }
271      else
272        cf2_computeDarkening( emRatio,
273                              ppem,
274                              font->stdVW,
275                              &font->darkenX,
276                              0,
277                              font->stemDarkened );
278
279#if 0
280      /* since hstem is measured in the y-direction, we use the `d' member */
281      /* of the fontMatrix                                                 */
282      /* TODO: use the same units per em as above; check this              */
283      emRatio = cf2_fixedFracMul( cf2_intToFixed( 1000 ), fontMatrix->d );
284#endif
285
286      /* set the default stem width, because it must be the same for all */
287      /* family members;                                                 */
288      /* choose a constant for StdHW that depends on font contrast       */
289      stdHW = cf2_getStdHW( decoder );
290
291      if ( stdHW > 0 && font->stdVW > 2 * stdHW )
292        font->stdHW = FT_DivFix( cf2_intToFixed( 75 ), emRatio );
293      else
294      {
295        /* low contrast font gets less hstem darkening */
296        font->stdHW = FT_DivFix( cf2_intToFixed( 110 ), emRatio );
297      }
298
299      cf2_computeDarkening( emRatio,
300                            ppem,
301                            font->stdHW,
302                            &font->darkenY,
303                            boldenY,
304                            font->stemDarkened );
305
306      if ( font->darkenX != 0 || font->darkenY != 0 )
307        font->darkened = TRUE;
308      else
309        font->darkened = FALSE;
310
311      font->reverseWinding = FALSE; /* initial expectation is CCW */
312
313      /* compute blue zones for this instance */
314      cf2_blues_init( &font->blues, font );
315    }
316  }
317
318
319  /* equivalent to AdobeGetOutline */
320  FT_LOCAL_DEF( FT_Error )
321  cf2_getGlyphOutline( CF2_Font           font,
322                       CF2_Buffer         charstring,
323                       const CF2_Matrix*  transform,
324                       CF2_F16Dot16*      glyphWidth )
325  {
326    FT_Error  lastError = FT_Err_Ok;
327
328    FT_Vector  translation;
329
330#if 0
331    FT_Vector  advancePoint;
332#endif
333
334    CF2_Fixed  advWidth = 0;
335    FT_Bool    needWinding;
336
337
338    /* Note: use both integer and fraction for outlines.  This allows bbox */
339    /*       to come out directly.                                         */
340
341    translation.x = transform->tx;
342    translation.y = transform->ty;
343
344    /* set up values based on transform */
345    cf2_font_setup( font, transform );
346    if ( font->error )
347      goto exit;                      /* setup encountered an error */
348
349    /* reset darken direction */
350    font->reverseWinding = FALSE;
351
352    /* winding order only affects darkening */
353    needWinding = font->darkened;
354
355    while ( 1 )
356    {
357      /* reset output buffer */
358      cf2_outline_reset( &font->outline );
359
360      /* build the outline, passing the full translation */
361      cf2_interpT2CharString( font,
362                              charstring,
363                              (CF2_OutlineCallbacks)&font->outline,
364                              &translation,
365                              FALSE,
366                              0,
367                              0,
368                              &advWidth );
369
370      if ( font->error )
371        goto exit;
372
373      if ( !needWinding )
374        break;
375
376      /* check winding order */
377      if ( font->outline.root.windingMomentum >= 0 ) /* CFF is CCW */
378        break;
379
380      /* invert darkening and render again                            */
381      /* TODO: this should be a parameter to getOutline-computeOffset */
382      font->reverseWinding = TRUE;
383
384      needWinding = FALSE;    /* exit after next iteration */
385    }
386
387    /* finish storing client outline */
388    cf2_outline_close( &font->outline );
389
390  exit:
391    /* FreeType just wants the advance width; there is no translation */
392    *glyphWidth = advWidth;
393
394    /* free resources and collect errors from objects we've used */
395    cf2_setError( &font->error, lastError );
396
397    return font->error;
398  }
399
400
401/* END */
402