thirdparty/freetype-2.3.12/src/base/ftlcdfil.c

   1 /***************************************************************************/
   2 /*                                                                         */
   3 /*  ftlcdfil.c                                                             */
   4 /*                                                                         */
   5 /*    FreeType API for color filtering of subpixel bitmap glyphs (body).   */
   6 /*                                                                         */
   7 /*  Copyright 2006, 2008, 2009 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 #include <ft2build.h>
  20 #include FT_LCD_FILTER_H
  21 #include FT_IMAGE_H
  22 #include FT_INTERNAL_OBJECTS_H
  23
  24
  25 #ifdef FT_CONFIG_OPTION_SUBPIXEL_RENDERING
  26
  27 /* define USE_LEGACY to implement the legacy filter */
  28 #define  USE_LEGACY
  29
  30   /* FIR filter used by the default and light filters */
  31   static void
  32   _ft_lcd_filter_fir( FT_Bitmap*      bitmap,
  33                       FT_Render_Mode  mode,
  34                       FT_Library      library )
  35   {
  36     FT_Byte*  weights = library->lcd_weights;
  37     FT_UInt   width   = (FT_UInt)bitmap->width;
  38     FT_UInt   height  = (FT_UInt)bitmap->rows;
  39
  40
  41     /* horizontal in-place FIR filter */
  42     if ( mode == FT_RENDER_MODE_LCD && width >= 4 )
  43     {
  44       FT_Byte*  line = bitmap->buffer;
  45
  46
  47       for ( ; height > 0; height--, line += bitmap->pitch )
  48       {
  49         FT_UInt  fir[5];
  50         FT_UInt  val1, xx;
  51
  52
  53         val1   = line[0];
  54         fir[0] = weights[2] * val1;
  55         fir[1] = weights[3] * val1;
  56         fir[2] = weights[4] * val1;
  57         fir[3] = 0;
  58         fir[4] = 0;
  59
  60         val1    = line[1];
  61         fir[0] += weights[1] * val1;
  62         fir[1] += weights[2] * val1;
  63         fir[2] += weights[3] * val1;
  64         fir[3] += weights[4] * val1;
  65
  66         for ( xx = 2; xx < width; xx++ )
  67         {
  68           FT_UInt  val, pix;
  69
  70
  71           val    = line[xx];
  72           pix    = fir[0] + weights[0] * val;
  73           fir[0] = fir[1] + weights[1] * val;
  74           fir[1] = fir[2] + weights[2] * val;
  75           fir[2] = fir[3] + weights[3] * val;
  76           fir[3] =          weights[4] * val;
  77
  78           pix        >>= 8;
  79           pix         |= -( pix >> 8 );
  80           line[xx - 2] = (FT_Byte)pix;
  81         }
  82
  83         {
  84           FT_UInt  pix;
  85
  86
  87           pix          = fir[0] >> 8;
  88           pix         |= -( pix >> 8 );
  89           line[xx - 2] = (FT_Byte)pix;
  90
  91           pix          = fir[1] >> 8;
  92           pix         |= -( pix >> 8 );
  93           line[xx - 1] = (FT_Byte)pix;
  94         }
  95       }
  96     }
  97
  98     /* vertical in-place FIR filter */
  99     else if ( mode == FT_RENDER_MODE_LCD_V && height >= 4 )
 100     {
 101       FT_Byte*  column = bitmap->buffer;
 102       FT_Int    pitch  = bitmap->pitch;
 103
 104
 105       for ( ; width > 0; width--, column++ )
 106       {
 107         FT_Byte*  col = column;
 108         FT_UInt   fir[5];
 109         FT_UInt   val1, yy;
 110
 111
 112         val1   = col[0];
 113         fir[0] = weights[2] * val1;
 114         fir[1] = weights[3] * val1;
 115         fir[2] = weights[4] * val1;
 116         fir[3] = 0;
 117         fir[4] = 0;
 118         col   += pitch;
 119
 120         val1    = col[0];
 121         fir[0] += weights[1] * val1;
 122         fir[1] += weights[2] * val1;
 123         fir[2] += weights[3] * val1;
 124         fir[3] += weights[4] * val1;
 125         col    += pitch;
 126
 127         for ( yy = 2; yy < height; yy++ )
 128         {
 129           FT_UInt  val, pix;
 130
 131
 132           val    = col[0];
 133           pix    = fir[0] + weights[0] * val;
 134           fir[0] = fir[1] + weights[1] * val;
 135           fir[1] = fir[2] + weights[2] * val;
 136           fir[2] = fir[3] + weights[3] * val;
 137           fir[3] =          weights[4] * val;
 138
 139           pix           >>= 8;
 140           pix            |= -( pix >> 8 );
 141           col[-2 * pitch] = (FT_Byte)pix;
 142           col            += pitch;
 143         }
 144
 145         {
 146           FT_UInt  pix;
 147
 148
 149           pix             = fir[0] >> 8;
 150           pix            |= -( pix >> 8 );
 151           col[-2 * pitch] = (FT_Byte)pix;
 152
 153           pix         = fir[1] >> 8;
 154           pix        |= -( pix >> 8 );
 155           col[-pitch] = (FT_Byte)pix;
 156         }
 157       }
 158     }
 159   }
 160
 161
 162 #ifdef USE_LEGACY
 163
 164   /* intra-pixel filter used by the legacy filter */
 165   static void
 166   _ft_lcd_filter_legacy( FT_Bitmap*      bitmap,
 167                          FT_Render_Mode  mode,
 168                          FT_Library      library )
 169   {
 170     FT_UInt  width  = (FT_UInt)bitmap->width;
 171     FT_UInt  height = (FT_UInt)bitmap->rows;
 172     FT_Int   pitch  = bitmap->pitch;
 173
 174     static const int  filters[3][3] =
 175     {
 176       { 65538 * 9/13, 65538 * 1/6, 65538 * 1/13 },
 177       { 65538 * 3/13, 65538 * 4/6, 65538 * 3/13 },
 178       { 65538 * 1/13, 65538 * 1/6, 65538 * 9/13 }
 179     };
 180
 181     FT_UNUSED( library );
 182
 183
 184     /* horizontal in-place intra-pixel filter */
 185     if ( mode == FT_RENDER_MODE_LCD && width >= 3 )
 186     {
 187       FT_Byte*  line = bitmap->buffer;
 188
 189
 190       for ( ; height > 0; height--, line += pitch )
 191       {
 192         FT_UInt  xx;
 193
 194
 195         for ( xx = 0; xx < width; xx += 3 )
 196         {
 197           FT_UInt  r = 0;
 198           FT_UInt  g = 0;
 199           FT_UInt  b = 0;
 200           FT_UInt  p;
 201
 202
 203           p  = line[xx];
 204           r += filters[0][0] * p;
 205           g += filters[0][1] * p;
 206           b += filters[0][2] * p;
 207
 208           p  = line[xx + 1];
 209           r += filters[1][0] * p;
 210           g += filters[1][1] * p;
 211           b += filters[1][2] * p;
 212
 213           p  = line[xx + 2];
 214           r += filters[2][0] * p;
 215           g += filters[2][1] * p;
 216           b += filters[2][2] * p;
 217
 218           line[xx]     = (FT_Byte)( r / 65536 );
 219           line[xx + 1] = (FT_Byte)( g / 65536 );
 220           line[xx + 2] = (FT_Byte)( b / 65536 );
 221         }
 222       }
 223     }
 224     else if ( mode == FT_RENDER_MODE_LCD_V && height >= 3 )
 225     {
 226       FT_Byte*  column = bitmap->buffer;
 227
 228
 229       for ( ; width > 0; width--, column++ )
 230       {
 231         FT_Byte*  col     = column;
 232         FT_Byte*  col_end = col + height * pitch;
 233
 234
 235         for ( ; col < col_end; col += 3 * pitch )
 236         {
 237           FT_UInt  r = 0;
 238           FT_UInt  g = 0;
 239           FT_UInt  b = 0;
 240           FT_UInt  p;
 241
 242
 243           p  = col[0];
 244           r += filters[0][0] * p;
 245           g += filters[0][1] * p;
 246           b += filters[0][2] * p;
 247
 248           p  = col[pitch];
 249           r += filters[1][0] * p;
 250           g += filters[1][1] * p;
 251           b += filters[1][2] * p;
 252
 253           p  = col[pitch * 2];
 254           r += filters[2][0] * p;
 255           g += filters[2][1] * p;
 256           b += filters[2][2] * p;
 257
 258           col[0]         = (FT_Byte)( r / 65536 );
 259           col[pitch]     = (FT_Byte)( g / 65536 );
 260           col[2 * pitch] = (FT_Byte)( b / 65536 );
 261         }
 262       }
 263     }
 264   }
 265
 266 #endif /* USE_LEGACY */
 267
 268
 269   FT_EXPORT_DEF( FT_Error )
 270   FT_Library_SetLcdFilter( FT_Library     library,
 271                            FT_LcdFilter   filter )
 272   {
 273     static const FT_Byte  light_filter[5] =
 274                             { 0, 85, 86, 85, 0 };
 275     /* the values here sum up to a value larger than 256, */
 276     /* providing a cheap gamma correction                 */
 277     static const FT_Byte  default_filter[5] =
 278                             { 0x10, 0x40, 0x70, 0x40, 0x10 };
 279
 280
 281     if ( library == NULL )
 282       return FT_Err_Invalid_Argument;
 283
 284     switch ( filter )
 285     {
 286     case FT_LCD_FILTER_NONE:
 287       library->lcd_filter_func = NULL;
 288       library->lcd_extra       = 0;
 289       break;
 290
 291     case FT_LCD_FILTER_DEFAULT:
 292 #if defined( FT_FORCE_LEGACY_LCD_FILTER )
 293
 294       library->lcd_filter_func = _ft_lcd_filter_legacy;
 295       library->lcd_extra       = 0;
 296
 297 #elif defined( FT_FORCE_LIGHT_LCD_FILTER )
 298
 299       ft_memcpy( library->lcd_weights, light_filter, 5 );
 300       library->lcd_filter_func = _ft_lcd_filter_fir;
 301       library->lcd_extra       = 2;
 302
 303 #else
 304
 305       ft_memcpy( library->lcd_weights, default_filter, 5 );
 306       library->lcd_filter_func = _ft_lcd_filter_fir;
 307       library->lcd_extra       = 2;
 308
 309 #endif
 310
 311       break;
 312
 313     case FT_LCD_FILTER_LIGHT:
 314       ft_memcpy( library->lcd_weights, light_filter, 5 );
 315       library->lcd_filter_func = _ft_lcd_filter_fir;
 316       library->lcd_extra       = 2;
 317       break;
 318
 319 #ifdef USE_LEGACY
 320
 321     case FT_LCD_FILTER_LEGACY:
 322       library->lcd_filter_func = _ft_lcd_filter_legacy;
 323       library->lcd_extra       = 0;
 324       break;
 325
 326 #endif
 327
 328     default:
 329       return FT_Err_Invalid_Argument;
 330     }
 331
 332     library->lcd_filter = filter;
 333     return 0;
 334   }
 335
 336 #else /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
 337
 338   FT_EXPORT_DEF( FT_Error )
 339   FT_Library_SetLcdFilter( FT_Library    library,
 340                            FT_LcdFilter  filter )
 341   {
 342     FT_UNUSED( library );
 343     FT_UNUSED( filter );
 344
 345     return FT_Err_Unimplemented_Feature;
 346   }
 347
 348 #endif /* !FT_CONFIG_OPTION_SUBPIXEL_RENDERING */
 349
 350
 351 /* END */