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 */ 352
