src/png/pngtrans.c

   1
   2 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
   3  *
   4  * Last changed in libpng 1.5.4 [July 7, 2011]
   5  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
   6  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   7  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   8  *
   9  * This code is released under the libpng license.
  10  * For conditions of distribution and use, see the disclaimer
  11  * and license in png.h
  12  */
  13
  14 #include "pngpriv.h"
  15
  16 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  17
  18 #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
  19 /* Turn on BGR-to-RGB mapping */
  20 void PNGAPI
  21 png_set_bgr(png_structp png_ptr)
  22 {
  23    png_debug(1, "in png_set_bgr");
  24
  25    if (png_ptr == NULL)
  26       return;
  27
  28    png_ptr->transformations |= PNG_BGR;
  29 }
  30 #endif
  31
  32 #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
  33 /* Turn on 16 bit byte swapping */
  34 void PNGAPI
  35 png_set_swap(png_structp png_ptr)
  36 {
  37    png_debug(1, "in png_set_swap");
  38
  39    if (png_ptr == NULL)
  40       return;
  41
  42    if (png_ptr->bit_depth == 16)
  43       png_ptr->transformations |= PNG_SWAP_BYTES;
  44 }
  45 #endif
  46
  47 #if defined(PNG_READ_PACK_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
  48 /* Turn on pixel packing */
  49 void PNGAPI
  50 png_set_packing(png_structp png_ptr)
  51 {
  52    png_debug(1, "in png_set_packing");
  53
  54    if (png_ptr == NULL)
  55       return;
  56
  57    if (png_ptr->bit_depth < 8)
  58    {
  59       png_ptr->transformations |= PNG_PACK;
  60       png_ptr->usr_bit_depth = 8;
  61    }
  62 }
  63 #endif
  64
  65 #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
  66 /* Turn on packed pixel swapping */
  67 void PNGAPI
  68 png_set_packswap(png_structp png_ptr)
  69 {
  70    png_debug(1, "in png_set_packswap");
  71
  72    if (png_ptr == NULL)
  73       return;
  74
  75    if (png_ptr->bit_depth < 8)
  76       png_ptr->transformations |= PNG_PACKSWAP;
  77 }
  78 #endif
  79
  80 #if defined(PNG_READ_SHIFT_SUPPORTED) || defined(PNG_WRITE_SHIFT_SUPPORTED)
  81 void PNGAPI
  82 png_set_shift(png_structp png_ptr, png_const_color_8p true_bits)
  83 {
  84    png_debug(1, "in png_set_shift");
  85
  86    if (png_ptr == NULL)
  87       return;
  88
  89    png_ptr->transformations |= PNG_SHIFT;
  90    png_ptr->shift = *true_bits;
  91 }
  92 #endif
  93
  94 #if defined(PNG_READ_INTERLACING_SUPPORTED) || \
  95     defined(PNG_WRITE_INTERLACING_SUPPORTED)
  96 int PNGAPI
  97 png_set_interlace_handling(png_structp png_ptr)
  98 {
  99    png_debug(1, "in png_set_interlace handling");
 100
 101    if (png_ptr && png_ptr->interlaced)
 102    {
 103       png_ptr->transformations |= PNG_INTERLACE;
 104       return (7);
 105    }
 106
 107    return (1);
 108 }
 109 #endif
 110
 111 #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
 112 /* Add a filler byte on read, or remove a filler or alpha byte on write.
 113  * The filler type has changed in v0.95 to allow future 2-byte fillers
 114  * for 48-bit input data, as well as to avoid problems with some compilers
 115  * that don't like bytes as parameters.
 116  */
 117 void PNGAPI
 118 png_set_filler(png_structp png_ptr, png_uint_32 filler, int filler_loc)
 119 {
 120    png_debug(1, "in png_set_filler");
 121
 122    if (png_ptr == NULL)
 123       return;
 124
 125    png_ptr->transformations |= PNG_FILLER;
 126    png_ptr->filler = (png_uint_16)filler;
 127
 128    if (filler_loc == PNG_FILLER_AFTER)
 129       png_ptr->flags |= PNG_FLAG_FILLER_AFTER;
 130
 131    else
 132       png_ptr->flags &= ~PNG_FLAG_FILLER_AFTER;
 133
 134    /* This should probably go in the "do_read_filler" routine.
 135     * I attempted to do that in libpng-1.0.1a but that caused problems
 136     * so I restored it in libpng-1.0.2a
 137    */
 138
 139    if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
 140    {
 141       png_ptr->usr_channels = 4;
 142    }
 143
 144    /* Also I added this in libpng-1.0.2a (what happens when we expand
 145     * a less-than-8-bit grayscale to GA?) */
 146
 147    if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY && png_ptr->bit_depth >= 8)
 148    {
 149       png_ptr->usr_channels = 2;
 150    }
 151 }
 152
 153 /* Added to libpng-1.2.7 */
 154 void PNGAPI
 155 png_set_add_alpha(png_structp png_ptr, png_uint_32 filler, int filler_loc)
 156 {
 157    png_debug(1, "in png_set_add_alpha");
 158
 159    if (png_ptr == NULL)
 160       return;
 161
 162    png_set_filler(png_ptr, filler, filler_loc);
 163    png_ptr->transformations |= PNG_ADD_ALPHA;
 164 }
 165
 166 #endif
 167
 168 #if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
 169     defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
 170 void PNGAPI
 171 png_set_swap_alpha(png_structp png_ptr)
 172 {
 173    png_debug(1, "in png_set_swap_alpha");
 174
 175    if (png_ptr == NULL)
 176       return;
 177
 178    png_ptr->transformations |= PNG_SWAP_ALPHA;
 179 }
 180 #endif
 181
 182 #if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
 183     defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
 184 void PNGAPI
 185 png_set_invert_alpha(png_structp png_ptr)
 186 {
 187    png_debug(1, "in png_set_invert_alpha");
 188
 189    if (png_ptr == NULL)
 190       return;
 191
 192    png_ptr->transformations |= PNG_INVERT_ALPHA;
 193 }
 194 #endif
 195
 196 #if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
 197 void PNGAPI
 198 png_set_invert_mono(png_structp png_ptr)
 199 {
 200    png_debug(1, "in png_set_invert_mono");
 201
 202    if (png_ptr == NULL)
 203       return;
 204
 205    png_ptr->transformations |= PNG_INVERT_MONO;
 206 }
 207
 208 /* Invert monochrome grayscale data */
 209 void /* PRIVATE */
 210 png_do_invert(png_row_infop row_info, png_bytep row)
 211 {
 212    png_debug(1, "in png_do_invert");
 213
 214   /* This test removed from libpng version 1.0.13 and 1.2.0:
 215    *   if (row_info->bit_depth == 1 &&
 216    */
 217    if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
 218    {
 219       png_bytep rp = row;
 220       png_size_t i;
 221       png_size_t istop = row_info->rowbytes;
 222
 223       for (i = 0; i < istop; i++)
 224       {
 225          *rp = (png_byte)(~(*rp));
 226          rp++;
 227       }
 228    }
 229
 230    else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
 231       row_info->bit_depth == 8)
 232    {
 233       png_bytep rp = row;
 234       png_size_t i;
 235       png_size_t istop = row_info->rowbytes;
 236
 237       for (i = 0; i < istop; i += 2)
 238       {
 239          *rp = (png_byte)(~(*rp));
 240          rp += 2;
 241       }
 242    }
 243
 244 #ifdef PNG_16BIT_SUPPORTED
 245    else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
 246       row_info->bit_depth == 16)
 247    {
 248       png_bytep rp = row;
 249       png_size_t i;
 250       png_size_t istop = row_info->rowbytes;
 251
 252       for (i = 0; i < istop; i += 4)
 253       {
 254          *rp = (png_byte)(~(*rp));
 255          *(rp + 1) = (png_byte)(~(*(rp + 1)));
 256          rp += 4;
 257       }
 258    }
 259 #endif
 260 }
 261 #endif
 262
 263 #ifdef PNG_16BIT_SUPPORTED
 264 #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
 265 /* Swaps byte order on 16 bit depth images */
 266 void /* PRIVATE */
 267 png_do_swap(png_row_infop row_info, png_bytep row)
 268 {
 269    png_debug(1, "in png_do_swap");
 270
 271    if (row_info->bit_depth == 16)
 272    {
 273       png_bytep rp = row;
 274       png_uint_32 i;
 275       png_uint_32 istop= row_info->width * row_info->channels;
 276
 277       for (i = 0; i < istop; i++, rp += 2)
 278       {
 279          png_byte t = *rp;
 280          *rp = *(rp + 1);
 281          *(rp + 1) = t;
 282       }
 283    }
 284 }
 285 #endif
 286 #endif
 287
 288 #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
 289 static PNG_CONST png_byte onebppswaptable[256] = {
 290    0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
 291    0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
 292    0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
 293    0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
 294    0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4,
 295    0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
 296    0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
 297    0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
 298    0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2,
 299    0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
 300    0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
 301    0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
 302    0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6,
 303    0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
 304    0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE,
 305    0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
 306    0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1,
 307    0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
 308    0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9,
 309    0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
 310    0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
 311    0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
 312    0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED,
 313    0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
 314    0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3,
 315    0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
 316    0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB,
 317    0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
 318    0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7,
 319    0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
 320    0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF,
 321    0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
 322 };
 323
 324 static PNG_CONST png_byte twobppswaptable[256] = {
 325    0x00, 0x40, 0x80, 0xC0, 0x10, 0x50, 0x90, 0xD0,
 326    0x20, 0x60, 0xA0, 0xE0, 0x30, 0x70, 0xB0, 0xF0,
 327    0x04, 0x44, 0x84, 0xC4, 0x14, 0x54, 0x94, 0xD4,
 328    0x24, 0x64, 0xA4, 0xE4, 0x34, 0x74, 0xB4, 0xF4,
 329    0x08, 0x48, 0x88, 0xC8, 0x18, 0x58, 0x98, 0xD8,
 330    0x28, 0x68, 0xA8, 0xE8, 0x38, 0x78, 0xB8, 0xF8,
 331    0x0C, 0x4C, 0x8C, 0xCC, 0x1C, 0x5C, 0x9C, 0xDC,
 332    0x2C, 0x6C, 0xAC, 0xEC, 0x3C, 0x7C, 0xBC, 0xFC,
 333    0x01, 0x41, 0x81, 0xC1, 0x11, 0x51, 0x91, 0xD1,
 334    0x21, 0x61, 0xA1, 0xE1, 0x31, 0x71, 0xB1, 0xF1,
 335    0x05, 0x45, 0x85, 0xC5, 0x15, 0x55, 0x95, 0xD5,
 336    0x25, 0x65, 0xA5, 0xE5, 0x35, 0x75, 0xB5, 0xF5,
 337    0x09, 0x49, 0x89, 0xC9, 0x19, 0x59, 0x99, 0xD9,
 338    0x29, 0x69, 0xA9, 0xE9, 0x39, 0x79, 0xB9, 0xF9,
 339    0x0D, 0x4D, 0x8D, 0xCD, 0x1D, 0x5D, 0x9D, 0xDD,
 340    0x2D, 0x6D, 0xAD, 0xED, 0x3D, 0x7D, 0xBD, 0xFD,
 341    0x02, 0x42, 0x82, 0xC2, 0x12, 0x52, 0x92, 0xD2,
 342    0x22, 0x62, 0xA2, 0xE2, 0x32, 0x72, 0xB2, 0xF2,
 343    0x06, 0x46, 0x86, 0xC6, 0x16, 0x56, 0x96, 0xD6,
 344    0x26, 0x66, 0xA6, 0xE6, 0x36, 0x76, 0xB6, 0xF6,
 345    0x0A, 0x4A, 0x8A, 0xCA, 0x1A, 0x5A, 0x9A, 0xDA,
 346    0x2A, 0x6A, 0xAA, 0xEA, 0x3A, 0x7A, 0xBA, 0xFA,
 347    0x0E, 0x4E, 0x8E, 0xCE, 0x1E, 0x5E, 0x9E, 0xDE,
 348    0x2E, 0x6E, 0xAE, 0xEE, 0x3E, 0x7E, 0xBE, 0xFE,
 349    0x03, 0x43, 0x83, 0xC3, 0x13, 0x53, 0x93, 0xD3,
 350    0x23, 0x63, 0xA3, 0xE3, 0x33, 0x73, 0xB3, 0xF3,
 351    0x07, 0x47, 0x87, 0xC7, 0x17, 0x57, 0x97, 0xD7,
 352    0x27, 0x67, 0xA7, 0xE7, 0x37, 0x77, 0xB7, 0xF7,
 353    0x0B, 0x4B, 0x8B, 0xCB, 0x1B, 0x5B, 0x9B, 0xDB,
 354    0x2B, 0x6B, 0xAB, 0xEB, 0x3B, 0x7B, 0xBB, 0xFB,
 355    0x0F, 0x4F, 0x8F, 0xCF, 0x1F, 0x5F, 0x9F, 0xDF,
 356    0x2F, 0x6F, 0xAF, 0xEF, 0x3F, 0x7F, 0xBF, 0xFF
 357 };
 358
 359 static PNG_CONST png_byte fourbppswaptable[256] = {
 360    0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70,
 361    0x80, 0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0,
 362    0x01, 0x11, 0x21, 0x31, 0x41, 0x51, 0x61, 0x71,
 363    0x81, 0x91, 0xA1, 0xB1, 0xC1, 0xD1, 0xE1, 0xF1,
 364    0x02, 0x12, 0x22, 0x32, 0x42, 0x52, 0x62, 0x72,
 365    0x82, 0x92, 0xA2, 0xB2, 0xC2, 0xD2, 0xE2, 0xF2,
 366    0x03, 0x13, 0x23, 0x33, 0x43, 0x53, 0x63, 0x73,
 367    0x83, 0x93, 0xA3, 0xB3, 0xC3, 0xD3, 0xE3, 0xF3,
 368    0x04, 0x14, 0x24, 0x34, 0x44, 0x54, 0x64, 0x74,
 369    0x84, 0x94, 0xA4, 0xB4, 0xC4, 0xD4, 0xE4, 0xF4,
 370    0x05, 0x15, 0x25, 0x35, 0x45, 0x55, 0x65, 0x75,
 371    0x85, 0x95, 0xA5, 0xB5, 0xC5, 0xD5, 0xE5, 0xF5,
 372    0x06, 0x16, 0x26, 0x36, 0x46, 0x56, 0x66, 0x76,
 373    0x86, 0x96, 0xA6, 0xB6, 0xC6, 0xD6, 0xE6, 0xF6,
 374    0x07, 0x17, 0x27, 0x37, 0x47, 0x57, 0x67, 0x77,
 375    0x87, 0x97, 0xA7, 0xB7, 0xC7, 0xD7, 0xE7, 0xF7,
 376    0x08, 0x18, 0x28, 0x38, 0x48, 0x58, 0x68, 0x78,
 377    0x88, 0x98, 0xA8, 0xB8, 0xC8, 0xD8, 0xE8, 0xF8,
 378    0x09, 0x19, 0x29, 0x39, 0x49, 0x59, 0x69, 0x79,
 379    0x89, 0x99, 0xA9, 0xB9, 0xC9, 0xD9, 0xE9, 0xF9,
 380    0x0A, 0x1A, 0x2A, 0x3A, 0x4A, 0x5A, 0x6A, 0x7A,
 381    0x8A, 0x9A, 0xAA, 0xBA, 0xCA, 0xDA, 0xEA, 0xFA,
 382    0x0B, 0x1B, 0x2B, 0x3B, 0x4B, 0x5B, 0x6B, 0x7B,
 383    0x8B, 0x9B, 0xAB, 0xBB, 0xCB, 0xDB, 0xEB, 0xFB,
 384    0x0C, 0x1C, 0x2C, 0x3C, 0x4C, 0x5C, 0x6C, 0x7C,
 385    0x8C, 0x9C, 0xAC, 0xBC, 0xCC, 0xDC, 0xEC, 0xFC,
 386    0x0D, 0x1D, 0x2D, 0x3D, 0x4D, 0x5D, 0x6D, 0x7D,
 387    0x8D, 0x9D, 0xAD, 0xBD, 0xCD, 0xDD, 0xED, 0xFD,
 388    0x0E, 0x1E, 0x2E, 0x3E, 0x4E, 0x5E, 0x6E, 0x7E,
 389    0x8E, 0x9E, 0xAE, 0xBE, 0xCE, 0xDE, 0xEE, 0xFE,
 390    0x0F, 0x1F, 0x2F, 0x3F, 0x4F, 0x5F, 0x6F, 0x7F,
 391    0x8F, 0x9F, 0xAF, 0xBF, 0xCF, 0xDF, 0xEF, 0xFF
 392 };
 393
 394 /* Swaps pixel packing order within bytes */
 395 void /* PRIVATE */
 396 png_do_packswap(png_row_infop row_info, png_bytep row)
 397 {
 398    png_debug(1, "in png_do_packswap");
 399
 400    if (row_info->bit_depth < 8)
 401    {
 402       png_bytep rp;
 403       png_const_bytep end, table;
 404
 405       end = row + row_info->rowbytes;
 406
 407       if (row_info->bit_depth == 1)
 408          table = onebppswaptable;
 409
 410       else if (row_info->bit_depth == 2)
 411          table = twobppswaptable;
 412
 413       else if (row_info->bit_depth == 4)
 414          table = fourbppswaptable;
 415
 416       else
 417          return;
 418
 419       for (rp = row; rp < end; rp++)
 420          *rp = table[*rp];
 421    }
 422 }
 423 #endif /* PNG_READ_PACKSWAP_SUPPORTED or PNG_WRITE_PACKSWAP_SUPPORTED */
 424
 425 #if defined(PNG_WRITE_FILLER_SUPPORTED) || \
 426     defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
 427 /* Remove a channel - this used to be 'png_do_strip_filler' but it used a
 428  * somewhat weird combination of flags to determine what to do.  All the calls
 429  * to png_do_strip_filler are changed in 1.5.2 to call this instead with the
 430  * correct arguments.
 431  *
 432  * The routine isn't general - the channel must be the channel at the start or
 433  * end (not in the middle) of each pixel.
 434  */
 435 void /* PRIVATE */
 436 png_do_strip_channel(png_row_infop row_info, png_bytep row, int at_start)
 437 {
 438    png_bytep sp = row; /* source pointer */
 439    png_bytep dp = row; /* destination pointer */
 440    png_bytep ep = row + row_info->rowbytes; /* One beyond end of row */
 441
 442    /* At the start sp will point to the first byte to copy and dp to where
 443     * it is copied to.  ep always points just beyond the end of the row, so
 444     * the loop simply copies (channels-1) channels until sp reaches ep.
 445     *
 446     * at_start:        0 -- convert AG, XG, ARGB, XRGB, AAGG, XXGG, etc.
 447     *            nonzero -- convert GA, GX, RGBA, RGBX, GGAA, RRGGBBXX, etc.
 448     */
 449
 450    /* GA, GX, XG cases */
 451    if (row_info->channels == 2)
 452    {
 453       if (row_info->bit_depth == 8)
 454       {
 455          if (at_start) /* Skip initial filler */
 456             ++sp;
 457          else          /* Skip initial channel and, for sp, the filler */
 458             sp += 2, ++dp;
 459
 460          /* For a 1 pixel wide image there is nothing to do */
 461          while (sp < ep)
 462             *dp++ = *sp, sp += 2;
 463
 464          row_info->pixel_depth = 8;
 465       }
 466
 467       else if (row_info->bit_depth == 16)
 468       {
 469          if (at_start) /* Skip initial filler */
 470             sp += 2;
 471          else          /* Skip initial channel and, for sp, the filler */
 472             sp += 4, dp += 2;
 473
 474          while (sp < ep)
 475             *dp++ = *sp++, *dp++ = *sp, sp += 3;
 476
 477          row_info->pixel_depth = 16;
 478       }
 479
 480       else
 481          return; /* bad bit depth */
 482
 483       row_info->channels = 1;
 484
 485       /* Finally fix the color type if it records an alpha channel */
 486       if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 487          row_info->color_type = PNG_COLOR_TYPE_GRAY;
 488    }
 489
 490    /* RGBA, RGBX, XRGB cases */
 491    else if (row_info->channels == 4)
 492    {
 493       if (row_info->bit_depth == 8)
 494       {
 495          if (at_start) /* Skip initial filler */
 496             ++sp;
 497          else          /* Skip initial channels and, for sp, the filler */
 498             sp += 4, dp += 3;
 499
 500          /* Note that the loop adds 3 to dp and 4 to sp each time. */
 501          while (sp < ep)
 502             *dp++ = *sp++, *dp++ = *sp++, *dp++ = *sp, sp += 2;
 503
 504          row_info->pixel_depth = 24;
 505       }
 506
 507       else if (row_info->bit_depth == 16)
 508       {
 509          if (at_start) /* Skip initial filler */
 510             sp += 2;
 511          else          /* Skip initial channels and, for sp, the filler */
 512             sp += 8, dp += 6;
 513
 514          while (sp < ep)
 515          {
 516             /* Copy 6 bytes, skip 2 */
 517             *dp++ = *sp++, *dp++ = *sp++;
 518             *dp++ = *sp++, *dp++ = *sp++;
 519             *dp++ = *sp++, *dp++ = *sp, sp += 3;
 520          }
 521
 522          row_info->pixel_depth = 48;
 523       }
 524
 525       else
 526          return; /* bad bit depth */
 527
 528       row_info->channels = 3;
 529
 530       /* Finally fix the color type if it records an alpha channel */
 531       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 532          row_info->color_type = PNG_COLOR_TYPE_RGB;
 533    }
 534
 535    else
 536       return; /* The filler channel has gone already */
 537
 538    /* Fix the rowbytes value. */
 539    row_info->rowbytes = dp-row;
 540 }
 541 #endif
 542
 543 #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
 544 /* Swaps red and blue bytes within a pixel */
 545 void /* PRIVATE */
 546 png_do_bgr(png_row_infop row_info, png_bytep row)
 547 {
 548    png_debug(1, "in png_do_bgr");
 549
 550    if ((row_info->color_type & PNG_COLOR_MASK_COLOR))
 551    {
 552       png_uint_32 row_width = row_info->width;
 553       if (row_info->bit_depth == 8)
 554       {
 555          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 556          {
 557             png_bytep rp;
 558             png_uint_32 i;
 559
 560             for (i = 0, rp = row; i < row_width; i++, rp += 3)
 561             {
 562                png_byte save = *rp;
 563                *rp = *(rp + 2);
 564                *(rp + 2) = save;
 565             }
 566          }
 567
 568          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 569          {
 570             png_bytep rp;
 571             png_uint_32 i;
 572
 573             for (i = 0, rp = row; i < row_width; i++, rp += 4)
 574             {
 575                png_byte save = *rp;
 576                *rp = *(rp + 2);
 577                *(rp + 2) = save;
 578             }
 579          }
 580       }
 581
 582 #ifdef PNG_16BIT_SUPPORTED
 583       else if (row_info->bit_depth == 16)
 584       {
 585          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 586          {
 587             png_bytep rp;
 588             png_uint_32 i;
 589
 590             for (i = 0, rp = row; i < row_width; i++, rp += 6)
 591             {
 592                png_byte save = *rp;
 593                *rp = *(rp + 4);
 594                *(rp + 4) = save;
 595                save = *(rp + 1);
 596                *(rp + 1) = *(rp + 5);
 597                *(rp + 5) = save;
 598             }
 599          }
 600
 601          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 602          {
 603             png_bytep rp;
 604             png_uint_32 i;
 605
 606             for (i = 0, rp = row; i < row_width; i++, rp += 8)
 607             {
 608                png_byte save = *rp;
 609                *rp = *(rp + 4);
 610                *(rp + 4) = save;
 611                save = *(rp + 1);
 612                *(rp + 1) = *(rp + 5);
 613                *(rp + 5) = save;
 614             }
 615          }
 616       }
 617 #endif
 618    }
 619 }
 620 #endif /* PNG_READ_BGR_SUPPORTED or PNG_WRITE_BGR_SUPPORTED */
 621
 622 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
 623     defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
 624 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
 625 void PNGAPI
 626 png_set_user_transform_info(png_structp png_ptr, png_voidp
 627    user_transform_ptr, int user_transform_depth, int user_transform_channels)
 628 {
 629    png_debug(1, "in png_set_user_transform_info");
 630
 631    if (png_ptr == NULL)
 632       return;
 633    png_ptr->user_transform_ptr = user_transform_ptr;
 634    png_ptr->user_transform_depth = (png_byte)user_transform_depth;
 635    png_ptr->user_transform_channels = (png_byte)user_transform_channels;
 636 }
 637 #endif
 638
 639 /* This function returns a pointer to the user_transform_ptr associated with
 640  * the user transform functions.  The application should free any memory
 641  * associated with this pointer before png_write_destroy and png_read_destroy
 642  * are called.
 643  */
 644 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
 645 png_voidp PNGAPI
 646 png_get_user_transform_ptr(png_const_structp png_ptr)
 647 {
 648    if (png_ptr == NULL)
 649       return (NULL);
 650
 651    return ((png_voidp)png_ptr->user_transform_ptr);
 652 }
 653 #endif
 654
 655 #ifdef PNG_USER_TRANSFORM_INFO_SUPPORTED
 656 png_uint_32 PNGAPI
 657 png_get_current_row_number(png_const_structp png_ptr)
 658 {
 659    /* See the comments in png.h - this is the sub-image row when reading and
 660     * interlaced image.
 661     */
 662    if (png_ptr != NULL)
 663       return png_ptr->row_number;
 664
 665    return PNG_UINT_32_MAX; /* help the app not to fail silently */
 666 }
 667
 668 png_byte PNGAPI
 669 png_get_current_pass_number(png_const_structp png_ptr)
 670 {
 671    if (png_ptr != NULL)
 672       return png_ptr->pass;
 673    return 8; /* invalid */
 674 }
 675 #endif /* PNG_USER_TRANSFORM_INFO_SUPPORTED */
 676 #endif /* PNG_READ_USER_TRANSFORM_SUPPORTED ||
 677           PNG_WRITE_USER_TRANSFORM_SUPPORTED */
 678 #endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */