aboutsummaryrefslogtreecommitdiff
path: root/freetype/src/base/ftlcdfil.c
blob: 3ed6d8191d5f4d77db40965658fd5ac044a3fed9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
/***************************************************************************/
/*                                                                         */
/*  ftlcdfil.c                                                             */
/*                                                                         */
/*    FreeType API for color filtering of subpixel bitmap glyphs (body).   */
/*                                                                         */
/*  Copyright 2006, 2008, 2009 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.                                        */
/*                                                                         */
/***************************************************************************/


#include <ft2build.h>
#include FT_LCD_FILTER_H
#include FT_IMAGE_H
#include <freetype/internal/ftobjs.h>


#ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING

/* define USE_LEGACY to implement the legacy filter */
#define  USE_LEGACY

  /* FIR filter used by the default and light filters */
  static void
  _ft_lcd_filter_fir( FT_Bitmap*      bitmap,
                      FT_Render_Mode  mode,
                      FT_Library      library )
  {
    FT_Byte*  weights = library->lcd_weights;
    FT_UInt   width   = (FT_UInt)bitmap->width;
    FT_UInt   height  = (FT_UInt)bitmap->rows;


    /* horizontal in-place FIR filter */
    if ( mode == FT_RENDER_MODE_LCD && width >= 4 )
    {
      FT_Byte*  line = bitmap->buffer;


      for ( ; height > 0; height--, line += bitmap->pitch )
      {
        FT_UInt  fir[5];
        FT_UInt  val1, xx;


        val1   = line[0];
        fir[0] = weights[2] * val1;
        fir[1] = weights[3] * val1;
        fir[2] = weights[4] * val1;
        fir[3] = 0;
        fir[4] = 0;

        val1    = line[1];
        fir[0] += weights[1] * val1;
        fir[1] += weights[2] * val1;
        fir[2] += weights[3] * val1;
        fir[3] += weights[4] * val1;

        for ( xx = 2; xx < width; xx++ )
        {
          FT_UInt  val, pix;


          val    = line[xx];
          pix    = fir[0] + weights[0] * val;
          fir[0] = fir[1] + weights[1] * val;
          fir[1] = fir[2] + weights[2] * val;
          fir[2] = fir[3] + weights[3] * val;
          fir[3] =          weights[4] * val;

          pix        >>= 8;
          pix         |= -( pix >> 8 );
          line[xx - 2] = (FT_Byte)pix;
        }

        {
          FT_UInt  pix;


          pix          = fir[0] >> 8;
          pix         |= -( pix >> 8 );
          line[xx - 2] = (FT_Byte)pix;

          pix          = fir[1] >> 8;
          pix         |= -( pix >> 8 );
          line[xx - 1] = (FT_Byte)pix;
        }
      }
    }

    /* vertical in-place FIR filter */
    else if ( mode == FT_RENDER_MODE_LCD_V && height >= 4 )
    {
      FT_Byte*  column = bitmap->buffer;
      FT_Int    pitch  = bitmap->pitch;


      for ( ; width > 0; width--, column++ )
      {
        FT_Byte*  col = column;
        FT_UInt   fir[5];
        FT_UInt   val1, yy;


        val1   = col[0];
        fir[0] = weights[2] * val1;
        fir[1] = weights[3] * val1;
        fir[2] = weights[4] * val1;
        fir[3] = 0;
        fir[4] = 0;
        col   += pitch;

        val1    = col[0];
        fir[0] += weights[1] * val1;
        fir[1] += weights[2] * val1;
        fir[2] += weights[3] * val1;
        fir[3] += weights[4] * val1;
        col    += pitch;

        for ( yy = 2; yy < height; yy++ )
        {
          FT_UInt  val, pix;


          val    = col[0];
          pix    = fir[0] + weights[0] * val;
          fir[0] = fir[1] + weights[1] * val;
          fir[1] = fir[2] + weights[2] * val;
          fir[2] = fir[3] + weights[3] * val;
          fir[3] =          weights[4] * val;

          pix           >>= 8;
          pix            |= -( pix >> 8 );
          col[-2 * pitch] = (FT_Byte)pix;
          col            += pitch;
        }

        {
          FT_UInt  pix;


          pix             = fir[0] >> 8;
          pix            |= -( pix >> 8 );
          col[-2 * pitch] = (FT_Byte)pix;

          pix         = fir[1] >> 8;
          pix        |= -( pix >> 8 );
          col[-pitch] = (FT_Byte)pix;
        }
      }
    }
  }


#ifdef USE_LEGACY

  /* intra-pixel filter used by the legacy filter */
  static void
  _ft_lcd_filter_legacy( FT_Bitmap*      bitmap,
                         FT_Render_Mode  mode,
                         FT_Library      library )
  {
    FT_UInt  width  = (FT_UInt)bitmap->width;
    FT_UInt  height = (FT_UInt)bitmap->rows;
    FT_Int   pitch  = bitmap->pitch;

    static const int  filters[3][3] =
    {
      { 65538 * 9/13, 65538 * 1/6, 65538 * 1/13 },
      { 65538 * 3/13, 65538 * 4/6, 65538 * 3/13 },
      { 65538 * 1/13, 65538 * 1/6, 65538 * 9/13 }
    };

    FT_UNUSED( library );


    /* horizontal in-place intra-pixel filter */
    if ( mode == FT_RENDER_MODE_LCD && width >= 3 )
    {
      FT_Byte*  line = bitmap->buffer;


      for ( ; height > 0; height--, line += pitch )
      {
        FT_UInt  xx;


        for ( xx = 0; xx < width; xx += 3 )
        {
          FT_UInt  r = 0;
          FT_UInt  g = 0;
          FT_UInt  b = 0;
          FT_UInt  p;


          p  = line[xx];
          r += filters[0][0] * p;
          g += filters[0][1] * p;
          b += filters[0][2] * p;

          p  = line[xx + 1];
          r += filters[1][0] * p;
          g += filters[1][1] * p;
          b += filters[1][2] * p;

          p  = line[xx + 2];
          r += filters[2][0] * p;
          g += filters[2][1] * p;
          b += filters[2][2] * p;

          line[xx]     = (FT_Byte)( r / 65536 );
          line[xx + 1] = (FT_Byte)( g / 65536 );
          line[xx + 2] = (FT_Byte)( b / 65536 );
        }
      }
    }
    else if ( mode == FT_RENDER_MODE_LCD_V && height >= 3 )
    {
      FT_Byte*  column = bitmap->buffer;


      for ( ; width > 0; width--, column++ )
      {
        FT_Byte*  col     = column;
        FT_Byte*  col_end = col + height * pitch;


        for ( ; col < col_end; col += 3 * pitch )
        {
          FT_UInt  r = 0;
          FT_UInt  g = 0;
          FT_UInt  b = 0;
          FT_UInt  p;


          p  = col[0];
          r += filters[0][0] * p;
          g += filters[0][1] * p;
          b += filters[0][2] * p;

          p  = col[pitch];
          r += filters[1][0] * p;
          g += filters[1][1] * p;
          b += filters[1][2] * p;

          p  = col[pitch * 2];
          r += filters[2][0] * p;
          g += filters[2][1] * p;
          b += filters[2][2] * p;

          col[0]         = (FT_Byte)( r / 65536 );
          col[pitch]     = (FT_Byte)( g / 65536 );
          col[2 * pitch] = (FT_Byte)( b / 65536 );
        }
      }
    }
  }

#endif /* USE_LEGACY */


  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdFilter( FT_Library     library,
                           FT_LcdFilter   filter )
  {
    static const FT_Byte  light_filter[5] =
                            { 0, 85, 86, 85, 0 };
    /* the values here sum up to a value larger than 256, */
    /* providing a cheap gamma correction                 */
    static const FT_Byte  default_filter[5] =
                            { 0x10, 0x40, 0x70, 0x40, 0x10 };


    if ( library == NULL )
      return FT_Err_Invalid_Argument;

    switch ( filter )
    {
    case FT_LCD_FILTER_NONE:
      library->lcd_filter_func = NULL;
      library->lcd_extra       = 0;
      break;

    case FT_LCD_FILTER_DEFAULT:
#if defined( FT_FORCE_LEGACY_LCD_FILTER )

      library->lcd_filter_func = _ft_lcd_filter_legacy;
      library->lcd_extra       = 0;

#elif defined( FT_FORCE_LIGHT_LCD_FILTER )

      ft_memcpy( library->lcd_weights, light_filter, 5 );
      library->lcd_filter_func = _ft_lcd_filter_fir;
      library->lcd_extra       = 2;

#else

      ft_memcpy( library->lcd_weights, default_filter, 5 );
      library->lcd_filter_func = _ft_lcd_filter_fir;
      library->lcd_extra       = 2;

#endif

      break;

    case FT_LCD_FILTER_LIGHT:
      ft_memcpy( library->lcd_weights, light_filter, 5 );
      library->lcd_filter_func = _ft_lcd_filter_fir;
      library->lcd_extra       = 2;
      break;

#ifdef USE_LEGACY

    case FT_LCD_FILTER_LEGACY:
      library->lcd_filter_func = _ft_lcd_filter_legacy;
      library->lcd_extra       = 0;
      break;

#endif

    default:
      return FT_Err_Invalid_Argument;
    }

    library->lcd_filter = filter;
    return 0;
  }

#else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */

  FT_EXPORT_DEF( FT_Error )
  FT_Library_SetLcdFilter( FT_Library    library,
                           FT_LcdFilter  filter )
  {
    FT_UNUSED( library );
    FT_UNUSED( filter );

    return FT_Err_Unimplemented_Feature;
  }

#endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */


/* END */