1/***************************************************************************/
2/*                                                                         */
3/*  cf2font.c                                                              */
4/*                                                                         */
5/*    Adobe's code for font instances (body).                              */
6/*                                                                         */
7/*  Copyright 2007-2014 Adobe Systems Incorporated.                        */
8/*                                                                         */
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35/*                                                                         */
36/***************************************************************************/
37
38
39#include <ft2build.h>
40#include FT_INTERNAL_CALC_H
41
42#include "cf2ft.h"
43
44#include "cf2glue.h"
45#include "cf2font.h"
46#include "cf2error.h"
47#include "cf2intrp.h"
48
49
50  /* Compute a stem darkening amount in character space. */
51  static void
52  cf2_computeDarkening( CF2_Fixed   emRatio,
53                        CF2_Fixed   ppem,
54                        CF2_Fixed   stemWidth,
55                        CF2_Fixed*  darkenAmount,
56                        CF2_Fixed   boldenAmount,
57                        FT_Bool     stemDarkened,
58                        FT_Int*     darkenParams )
59  {
60    /*
61     * Total darkening amount is computed in 1000 unit character space
62     * using the modified 5 part curve as Adobe's Avalon rasterizer.
63     * The darkening amount is smaller for thicker stems.
64     * It becomes zero when the stem is thicker than 2.333 pixels.
65     *
66     * By default, we use
67     *
68     *   darkenAmount = 0.4 pixels   if scaledStem <= 0.5 pixels,
69     *   darkenAmount = 0.275 pixels if 1 <= scaledStem <= 1.667 pixels,
70     *   darkenAmount = 0 pixel      if scaledStem >= 2.333 pixels,
71     *
72     * and piecewise linear in-between:
73     *
74     *
75     *   darkening
76     *       ^
77     *       |
78     *       |      (x1,y1)
79     *       |--------+
80     *       |         \
81     *       |          \
82     *       |           \          (x3,y3)
83     *       |            +----------+
84     *       |        (x2,y2)         \
85     *       |                         \
86     *       |                          \
87     *       |                           +-----------------
88     *       |                         (x4,y4)
89     *       +--------------------------------------------->   stem
90     *                                                       thickness
91     *
92     *
93     * This corresponds to the following values for the
94     * `darkening-parameters' property:
95     *
96     *   (x1, y1) = (500, 400)
97     *   (x2, y2) = (1000, 275)
98     *   (x3, y3) = (1667, 275)
99     *   (x4, y4) = (2333, 0)
100     *
101     */
102
103    /* Internal calculations are done in units per thousand for */
104    /* convenience. The x axis is scaled stem width in          */
105    /* thousandths of a pixel. That is, 1000 is 1 pixel.        */
106    /* The y axis is darkening amount in thousandths of a pixel.*/
107    /* In the code, below, dividing by ppem and                 */
108    /* adjusting for emRatio converts darkenAmount to character */
109    /* space (font units).                                      */
110    CF2_Fixed  stemWidthPer1000, scaledStem;
111    FT_Int     logBase2;
112
113
114    *darkenAmount = 0;
115
116    if ( boldenAmount == 0 && !stemDarkened )
117      return;
118
119    /* protect against range problems and divide by zero */
120    if ( emRatio < cf2_floatToFixed( .01 ) )
121      return;
122
123    if ( stemDarkened )
124    {
125      FT_Int  x1 = darkenParams[0];
126      FT_Int  y1 = darkenParams[1];
127      FT_Int  x2 = darkenParams[2];
128      FT_Int  y2 = darkenParams[3];
129      FT_Int  x3 = darkenParams[4];
130      FT_Int  y3 = darkenParams[5];
131      FT_Int  x4 = darkenParams[6];
132      FT_Int  y4 = darkenParams[7];
133
134
135      /* convert from true character space to 1000 unit character space; */
136      /* add synthetic emboldening effect                                */
137
138      /* `stemWidthPer1000' will not overflow for a legitimate font      */
139
140      stemWidthPer1000 = FT_MulFix( stemWidth + boldenAmount, emRatio );
141
142      /* `scaledStem' can easily overflow, so we must clamp its maximum  */
143      /* value; the test doesn't need to be precise, but must be         */
144      /* conservative.  The clamp value (default 2333) where             */
145      /* `darkenAmount' is zero is well below the overflow value of      */
146      /* 32767.                                                          */
147      /*                                                                 */
148      /* FT_MSB computes the integer part of the base 2 logarithm.  The  */
149      /* number of bits for the product is 1 or 2 more than the sum of   */
150      /* logarithms; remembering that the 16 lowest bits of the fraction */
151      /* are dropped this is correct to within a factor of almost 4.     */
152      /* For example, 0x80.0000 * 0x80.0000 = 0x4000.0000 is 23+23 and   */
153      /* is flagged as possible overflow because 0xff.ffff * 0xff.ffff = */
154      /* 0xffff.fe00 is also 23+23.                                      */
155
156      logBase2 = FT_MSB( (FT_UInt32)stemWidthPer1000 ) +
157                   FT_MSB( (FT_UInt32)ppem );
158
159      if ( logBase2 >= 46 )
160        /* possible overflow */
161        scaledStem = cf2_intToFixed( x4 );
162      else
163        scaledStem = FT_MulFix( stemWidthPer1000, ppem );
164
165      /* now apply the darkening parameters */
166
167      if ( scaledStem < cf2_intToFixed( x1 ) )
168        *darkenAmount = FT_DivFix( cf2_intToFixed( y1 ), ppem );
169
170      else if ( scaledStem < cf2_intToFixed( x2 ) )
171      {
172        FT_Int  xdelta = x2 - x1;
173        FT_Int  ydelta = y2 - y1;
174        FT_Int  x      = stemWidthPer1000 -
175                           FT_DivFix( cf2_intToFixed( x1 ), ppem );
176
177
178        if ( !xdelta )
179          goto Try_x3;
180
181        *darkenAmount = FT_MulDiv( x, ydelta, xdelta ) +
182                          FT_DivFix( cf2_intToFixed( y1 ), ppem );
183      }
184
185      else if ( scaledStem < cf2_intToFixed( x3 ) )
186      {
187      Try_x3:
188        {
189          FT_Int  xdelta = x3 - x2;
190          FT_Int  ydelta = y3 - y2;
191          FT_Int  x      = stemWidthPer1000 -
192                             FT_DivFix( cf2_intToFixed( x2 ), ppem );
193
194
195          if ( !xdelta )
196            goto Try_x4;
197
198          *darkenAmount = FT_MulDiv( x, ydelta, xdelta ) +
199                            FT_DivFix( cf2_intToFixed( y2 ), ppem );
200        }
201      }
202
203      else if ( scaledStem < cf2_intToFixed( x4 ) )
204      {
205      Try_x4:
206        {
207          FT_Int  xdelta = x4 - x3;
208          FT_Int  ydelta = y4 - y3;
209          FT_Int  x      = stemWidthPer1000 -
210                             FT_DivFix( cf2_intToFixed( x3 ), ppem );
211
212
213          if ( !xdelta )
214            goto Use_y4;
215
216          *darkenAmount = FT_MulDiv( x, ydelta, xdelta ) +
217                            FT_DivFix( cf2_intToFixed( y3 ), ppem );
218        }
219      }
220
221      else
222      {
223      Use_y4:
224        *darkenAmount = FT_DivFix( cf2_intToFixed( y4 ), ppem );
225      }
226
227      /* use half the amount on each side and convert back to true */
228      /* character space                                           */
229      *darkenAmount = FT_DivFix( *darkenAmount, 2 * emRatio );
230    }
231
232    /* add synthetic emboldening effect in character space */
233    *darkenAmount += boldenAmount / 2;
234  }
235
236
237  /* set up values for the current FontDict and matrix */
238
239  /* caller's transform is adjusted for subpixel positioning */
240  static void
241  cf2_font_setup( CF2_Font           font,
242                  const CF2_Matrix*  transform )
243  {
244    /* pointer to parsed font object */
245    CFF_Decoder*  decoder = font->decoder;
246
247    FT_Bool  needExtraSetup = FALSE;
248
249    /* character space units */
250    CF2_Fixed  boldenX = font->syntheticEmboldeningAmountX;
251    CF2_Fixed  boldenY = font->syntheticEmboldeningAmountY;
252
253    CFF_SubFont  subFont;
254    CF2_Fixed    ppem;
255
256
257    /* clear previous error */
258    font->error = FT_Err_Ok;
259
260    /* if a CID fontDict has changed, we need to recompute some cached */
261    /* data                                                            */
262    subFont = cf2_getSubfont( decoder );
263    if ( font->lastSubfont != subFont )
264    {
265      font->lastSubfont = subFont;
266      needExtraSetup    = TRUE;
267    }
268
269    /* if ppem has changed, we need to recompute some cached data         */
270    /* note: because of CID font matrix concatenation, ppem and transform */
271    /*       do not necessarily track.                                    */
272    ppem = cf2_getPpemY( decoder );
273    if ( font->ppem != ppem )
274    {
275      font->ppem     = ppem;
276      needExtraSetup = TRUE;
277    }
278
279    /* copy hinted flag on each call */
280    font->hinted = (FT_Bool)( font->renderingFlags & CF2_FlagsHinted );
281
282    /* determine if transform has changed;       */
283    /* include Fontmatrix but ignore translation */
284    if ( ft_memcmp( transform,
285                    &font->currentTransform,
286                    4 * sizeof ( CF2_Fixed ) ) != 0 )
287    {
288      /* save `key' information for `cache of one' matrix data; */
289      /* save client transform, without the translation         */
290      font->currentTransform    = *transform;
291      font->currentTransform.tx =
292      font->currentTransform.ty = cf2_intToFixed( 0 );
293
294      /* TODO: FreeType transform is simple scalar; for now, use identity */
295      /*       for outer                                                  */
296      font->innerTransform   = *transform;
297      font->outerTransform.a =
298      font->outerTransform.d = cf2_intToFixed( 1 );
299      font->outerTransform.b =
300      font->outerTransform.c = cf2_intToFixed( 0 );
301
302      needExtraSetup = TRUE;
303    }
304
305    /*
306     * font->darkened is set to true if there is a stem darkening request or
307     * the font is synthetic emboldened.
308     * font->darkened controls whether to adjust blue zones, winding order,
309     * and hinting.
310     *
311     */
312    if ( font->stemDarkened != ( font->renderingFlags & CF2_FlagsDarkened ) )
313    {
314      font->stemDarkened =
315        (FT_Bool)( font->renderingFlags & CF2_FlagsDarkened );
316
317      /* blue zones depend on darkened flag */
318      needExtraSetup = TRUE;
319    }
320
321    /* recompute variables that are dependent on transform or FontDict or */
322    /* darken flag                                                        */
323    if ( needExtraSetup )
324    {
325      /* StdVW is found in the private dictionary;                       */
326      /* recompute darkening amounts whenever private dictionary or      */
327      /* transform change                                                */
328      /* Note: a rendering flag turns darkening on or off, so we want to */
329      /*       store the `on' amounts;                                   */
330      /*       darkening amount is computed in character space           */
331      /* TODO: testing size-dependent darkening here;                    */
332      /*       what to do for rotations?                                 */
333
334      CF2_Fixed  emRatio;
335      CF2_Fixed  stdHW;
336      CF2_Int    unitsPerEm = font->unitsPerEm;
337
338
339      if ( unitsPerEm == 0 )
340        unitsPerEm = 1000;
341
342      ppem = FT_MAX( cf2_intToFixed( 4 ),
343                     font->ppem ); /* use minimum ppem of 4 */
344
345#if 0
346      /* since vstem is measured in the x-direction, we use the `a' member */
347      /* of the fontMatrix                                                 */
348      emRatio = cf2_fixedFracMul( cf2_intToFixed( 1000 ), fontMatrix->a );
349#endif
350
351      /* Freetype does not preserve the fontMatrix when parsing; use */
352      /* unitsPerEm instead.                                         */
353      /* TODO: check precision of this                               */
354      emRatio     = cf2_intToFixed( 1000 ) / unitsPerEm;
355      font->stdVW = cf2_getStdVW( decoder );
356
357      if ( font->stdVW <= 0 )
358        font->stdVW = FT_DivFix( cf2_intToFixed( 75 ), emRatio );
359
360      if ( boldenX > 0 )
361      {
362        /* Ensure that boldenX is at least 1 pixel for synthetic bold font */
363        /* (similar to what Avalon does)                                   */
364        boldenX = FT_MAX( boldenX,
365                          FT_DivFix( cf2_intToFixed( unitsPerEm ), ppem ) );
366
367        /* Synthetic emboldening adds at least 1 pixel to darkenX, while */
368        /* stem darkening adds at most half pixel.  Since the purpose of */
369        /* stem darkening (readability at small sizes) is met with       */
370        /* synthetic emboldening, no need to add stem darkening for a    */
371        /* synthetic bold font.                                          */
372        cf2_computeDarkening( emRatio,
373                              ppem,
374                              font->stdVW,
375                              &font->darkenX,
376                              boldenX,
377                              FALSE,
378                              font->darkenParams );
379      }
380      else
381        cf2_computeDarkening( emRatio,
382                              ppem,
383                              font->stdVW,
384                              &font->darkenX,
385                              0,
386                              font->stemDarkened,
387                              font->darkenParams );
388
389#if 0
390      /* since hstem is measured in the y-direction, we use the `d' member */
391      /* of the fontMatrix                                                 */
392      /* TODO: use the same units per em as above; check this              */
393      emRatio = cf2_fixedFracMul( cf2_intToFixed( 1000 ), fontMatrix->d );
394#endif
395
396      /* set the default stem width, because it must be the same for all */
397      /* family members;                                                 */
398      /* choose a constant for StdHW that depends on font contrast       */
399      stdHW = cf2_getStdHW( decoder );
400
401      if ( stdHW > 0 && font->stdVW > 2 * stdHW )
402        font->stdHW = FT_DivFix( cf2_intToFixed( 75 ), emRatio );
403      else
404      {
405        /* low contrast font gets less hstem darkening */
406        font->stdHW = FT_DivFix( cf2_intToFixed( 110 ), emRatio );
407      }
408
409      cf2_computeDarkening( emRatio,
410                            ppem,
411                            font->stdHW,
412                            &font->darkenY,
413                            boldenY,
414                            font->stemDarkened,
415                            font->darkenParams );
416
417      if ( font->darkenX != 0 || font->darkenY != 0 )
418        font->darkened = TRUE;
419      else
420        font->darkened = FALSE;
421
422      font->reverseWinding = FALSE; /* initial expectation is CCW */
423
424      /* compute blue zones for this instance */
425      cf2_blues_init( &font->blues, font );
426    }
427  }
428
429
430  /* equivalent to AdobeGetOutline */
431  FT_LOCAL_DEF( FT_Error )
432  cf2_getGlyphOutline( CF2_Font           font,
433                       CF2_Buffer         charstring,
434                       const CF2_Matrix*  transform,
435                       CF2_F16Dot16*      glyphWidth )
436  {
437    FT_Error  lastError = FT_Err_Ok;
438
439    FT_Vector  translation;
440
441#if 0
442    FT_Vector  advancePoint;
443#endif
444
445    CF2_Fixed  advWidth = 0;
446    FT_Bool    needWinding;
447
448
449    /* Note: use both integer and fraction for outlines.  This allows bbox */
450    /*       to come out directly.                                         */
451
452    translation.x = transform->tx;
453    translation.y = transform->ty;
454
455    /* set up values based on transform */
456    cf2_font_setup( font, transform );
457    if ( font->error )
458      goto exit;                      /* setup encountered an error */
459
460    /* reset darken direction */
461    font->reverseWinding = FALSE;
462
463    /* winding order only affects darkening */
464    needWinding = font->darkened;
465
466    while ( 1 )
467    {
468      /* reset output buffer */
469      cf2_outline_reset( &font->outline );
470
471      /* build the outline, passing the full translation */
472      cf2_interpT2CharString( font,
473                              charstring,
474                              (CF2_OutlineCallbacks)&font->outline,
475                              &translation,
476                              FALSE,
477                              0,
478                              0,
479                              &advWidth );
480
481      if ( font->error )
482        goto exit;
483
484      if ( !needWinding )
485        break;
486
487      /* check winding order */
488      if ( font->outline.root.windingMomentum >= 0 ) /* CFF is CCW */
489        break;
490
491      /* invert darkening and render again                            */
492      /* TODO: this should be a parameter to getOutline-computeOffset */
493      font->reverseWinding = TRUE;
494
495      needWinding = FALSE;    /* exit after next iteration */
496    }
497
498    /* finish storing client outline */
499    cf2_outline_close( &font->outline );
500
501  exit:
502    /* FreeType just wants the advance width; there is no translation */
503    *glyphWidth = advWidth;
504
505    /* free resources and collect errors from objects we've used */
506    cf2_setError( &font->error, lastError );
507
508    return font->error;
509  }
510
511
512/* END */
513