1 /*
   2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.  Oracle designates this
   7  * particular file as subject to the "Classpath" exception as provided
   8  * by Oracle in the LICENSE file that accompanied this code.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  */
  24 
  25 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  26  *
  27  * This file is available under and governed by the GNU General Public
  28  * License version 2 only, as published by the Free Software Foundation.
  29  * However, the following notice accompanied the original version of this
  30  * file and, per its terms, should not be removed:
  31  *
  32  * Last changed in libpng 1.6.26 [October 20, 2016]
  33  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  34  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  35  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  36  *
  37  * This code is released under the libpng license.
  38  * For conditions of distribution and use, see the disclaimer
  39  * and license in png.h
  40  */
  41 
  42 #include "pngpriv.h"
  43 
  44 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  45 
  46 #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
  47 /* Turn on BGR-to-RGB mapping */
  48 void PNGAPI
  49 png_set_bgr(png_structrp png_ptr)
  50 {
  51    png_debug(1, "in png_set_bgr");
  52 
  53    if (png_ptr == NULL)
  54       return;
  55 
  56    png_ptr->transformations |= PNG_BGR;
  57 }
  58 #endif
  59 
  60 #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
  61 /* Turn on 16-bit byte swapping */
  62 void PNGAPI
  63 png_set_swap(png_structrp png_ptr)
  64 {
  65    png_debug(1, "in png_set_swap");
  66 
  67    if (png_ptr == NULL)
  68       return;
  69 
  70    if (png_ptr->bit_depth == 16)
  71       png_ptr->transformations |= PNG_SWAP_BYTES;
  72 }
  73 #endif
  74 
  75 #if defined(PNG_READ_PACK_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
  76 /* Turn on pixel packing */
  77 void PNGAPI
  78 png_set_packing(png_structrp png_ptr)
  79 {
  80    png_debug(1, "in png_set_packing");
  81 
  82    if (png_ptr == NULL)
  83       return;
  84 
  85    if (png_ptr->bit_depth < 8)
  86    {
  87       png_ptr->transformations |= PNG_PACK;
  88 #     ifdef PNG_WRITE_SUPPORTED
  89          png_ptr->usr_bit_depth = 8;
  90 #     endif
  91    }
  92 }
  93 #endif
  94 
  95 #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
  96 /* Turn on packed pixel swapping */
  97 void PNGAPI
  98 png_set_packswap(png_structrp png_ptr)
  99 {
 100    png_debug(1, "in png_set_packswap");
 101 
 102    if (png_ptr == NULL)
 103       return;
 104 
 105    if (png_ptr->bit_depth < 8)
 106       png_ptr->transformations |= PNG_PACKSWAP;
 107 }
 108 #endif
 109 
 110 #if defined(PNG_READ_SHIFT_SUPPORTED) || defined(PNG_WRITE_SHIFT_SUPPORTED)
 111 void PNGAPI
 112 png_set_shift(png_structrp png_ptr, png_const_color_8p true_bits)
 113 {
 114    png_debug(1, "in png_set_shift");
 115 
 116    if (png_ptr == NULL)
 117       return;
 118 
 119    png_ptr->transformations |= PNG_SHIFT;
 120    png_ptr->shift = *true_bits;
 121 }
 122 #endif
 123 
 124 #if defined(PNG_READ_INTERLACING_SUPPORTED) || \
 125     defined(PNG_WRITE_INTERLACING_SUPPORTED)
 126 int PNGAPI
 127 png_set_interlace_handling(png_structrp png_ptr)
 128 {
 129    png_debug(1, "in png_set_interlace handling");
 130 
 131    if (png_ptr != 0 && png_ptr->interlaced != 0)
 132    {
 133       png_ptr->transformations |= PNG_INTERLACE;
 134       return (7);
 135    }
 136 
 137    return (1);
 138 }
 139 #endif
 140 
 141 #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
 142 /* Add a filler byte on read, or remove a filler or alpha byte on write.
 143  * The filler type has changed in v0.95 to allow future 2-byte fillers
 144  * for 48-bit input data, as well as to avoid problems with some compilers
 145  * that don't like bytes as parameters.
 146  */
 147 void PNGAPI
 148 png_set_filler(png_structrp png_ptr, png_uint_32 filler, int filler_loc)
 149 {
 150    png_debug(1, "in png_set_filler");
 151 
 152    if (png_ptr == NULL)
 153       return;
 154 
 155    /* In libpng 1.6 it is possible to determine whether this is a read or write
 156     * operation and therefore to do more checking here for a valid call.
 157     */
 158    if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
 159    {
 160 #     ifdef PNG_READ_FILLER_SUPPORTED
 161          /* On read png_set_filler is always valid, regardless of the base PNG
 162           * format, because other transformations can give a format where the
 163           * filler code can execute (basically an 8 or 16-bit component RGB or G
 164           * format.)
 165           *
 166           * NOTE: usr_channels is not used by the read code!  (This has led to
 167           * confusion in the past.)  The filler is only used in the read code.
 168           */
 169          png_ptr->filler = (png_uint_16)filler;
 170 #     else
 171          png_app_error(png_ptr, "png_set_filler not supported on read");
 172          PNG_UNUSED(filler) /* not used in the write case */
 173          return;
 174 #     endif
 175    }
 176 
 177    else /* write */
 178    {
 179 #     ifdef PNG_WRITE_FILLER_SUPPORTED
 180          /* On write the usr_channels parameter must be set correctly at the
 181           * start to record the number of channels in the app-supplied data.
 182           */
 183          switch (png_ptr->color_type)
 184          {
 185             case PNG_COLOR_TYPE_RGB:
 186                png_ptr->usr_channels = 4;
 187                break;
 188 
 189             case PNG_COLOR_TYPE_GRAY:
 190                if (png_ptr->bit_depth >= 8)
 191                {
 192                   png_ptr->usr_channels = 2;
 193                   break;
 194                }
 195 
 196                else
 197                {
 198                   /* There simply isn't any code in libpng to strip out bits
 199                    * from bytes when the components are less than a byte in
 200                    * size!
 201                    */
 202                   png_app_error(png_ptr,
 203                       "png_set_filler is invalid for"
 204                       " low bit depth gray output");
 205                   return;
 206                }
 207 
 208             default:
 209                png_app_error(png_ptr,
 210                    "png_set_filler: inappropriate color type");
 211                return;
 212          }
 213 #     else
 214          png_app_error(png_ptr, "png_set_filler not supported on write");
 215          return;
 216 #     endif
 217    }
 218 
 219    /* Here on success - libpng supports the operation, set the transformation
 220     * and the flag to say where the filler channel is.
 221     */
 222    png_ptr->transformations |= PNG_FILLER;
 223 
 224    if (filler_loc == PNG_FILLER_AFTER)
 225       png_ptr->flags |= PNG_FLAG_FILLER_AFTER;
 226 
 227    else
 228       png_ptr->flags &= ~PNG_FLAG_FILLER_AFTER;
 229 }
 230 
 231 /* Added to libpng-1.2.7 */
 232 void PNGAPI
 233 png_set_add_alpha(png_structrp png_ptr, png_uint_32 filler, int filler_loc)
 234 {
 235    png_debug(1, "in png_set_add_alpha");
 236 
 237    if (png_ptr == NULL)
 238       return;
 239 
 240    png_set_filler(png_ptr, filler, filler_loc);
 241    /* The above may fail to do anything. */
 242    if ((png_ptr->transformations & PNG_FILLER) != 0)
 243       png_ptr->transformations |= PNG_ADD_ALPHA;
 244 }
 245 
 246 #endif
 247 
 248 #if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
 249     defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
 250 void PNGAPI
 251 png_set_swap_alpha(png_structrp png_ptr)
 252 {
 253    png_debug(1, "in png_set_swap_alpha");
 254 
 255    if (png_ptr == NULL)
 256       return;
 257 
 258    png_ptr->transformations |= PNG_SWAP_ALPHA;
 259 }
 260 #endif
 261 
 262 #if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
 263     defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
 264 void PNGAPI
 265 png_set_invert_alpha(png_structrp png_ptr)
 266 {
 267    png_debug(1, "in png_set_invert_alpha");
 268 
 269    if (png_ptr == NULL)
 270       return;
 271 
 272    png_ptr->transformations |= PNG_INVERT_ALPHA;
 273 }
 274 #endif
 275 
 276 #if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
 277 void PNGAPI
 278 png_set_invert_mono(png_structrp png_ptr)
 279 {
 280    png_debug(1, "in png_set_invert_mono");
 281 
 282    if (png_ptr == NULL)
 283       return;
 284 
 285    png_ptr->transformations |= PNG_INVERT_MONO;
 286 }
 287 
 288 /* Invert monochrome grayscale data */
 289 void /* PRIVATE */
 290 png_do_invert(png_row_infop row_info, png_bytep row)
 291 {
 292    png_debug(1, "in png_do_invert");
 293 
 294   /* This test removed from libpng version 1.0.13 and 1.2.0:
 295    *   if (row_info->bit_depth == 1 &&
 296    */
 297    if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
 298    {
 299       png_bytep rp = row;
 300       png_size_t i;
 301       png_size_t istop = row_info->rowbytes;
 302 
 303       for (i = 0; i < istop; i++)
 304       {
 305          *rp = (png_byte)(~(*rp));
 306          rp++;
 307       }
 308    }
 309 
 310    else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
 311       row_info->bit_depth == 8)
 312    {
 313       png_bytep rp = row;
 314       png_size_t i;
 315       png_size_t istop = row_info->rowbytes;
 316 
 317       for (i = 0; i < istop; i += 2)
 318       {
 319          *rp = (png_byte)(~(*rp));
 320          rp += 2;
 321       }
 322    }
 323 
 324 #ifdef PNG_16BIT_SUPPORTED
 325    else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
 326       row_info->bit_depth == 16)
 327    {
 328       png_bytep rp = row;
 329       png_size_t i;
 330       png_size_t istop = row_info->rowbytes;
 331 
 332       for (i = 0; i < istop; i += 4)
 333       {
 334          *rp = (png_byte)(~(*rp));
 335          *(rp + 1) = (png_byte)(~(*(rp + 1)));
 336          rp += 4;
 337       }
 338    }
 339 #endif
 340 }
 341 #endif
 342 
 343 #ifdef PNG_16BIT_SUPPORTED
 344 #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
 345 /* Swaps byte order on 16-bit depth images */
 346 void /* PRIVATE */
 347 png_do_swap(png_row_infop row_info, png_bytep row)
 348 {
 349    png_debug(1, "in png_do_swap");
 350 
 351    if (row_info->bit_depth == 16)
 352    {
 353       png_bytep rp = row;
 354       png_uint_32 i;
 355       png_uint_32 istop= row_info->width * row_info->channels;
 356 
 357       for (i = 0; i < istop; i++, rp += 2)
 358       {
 359 #ifdef PNG_BUILTIN_BSWAP16_SUPPORTED
 360          /* Feature added to libpng-1.6.11 for testing purposes, not
 361           * enabled by default.
 362           */
 363          *(png_uint_16*)rp = __builtin_bswap16(*(png_uint_16*)rp);
 364 #else
 365          png_byte t = *rp;
 366          *rp = *(rp + 1);
 367          *(rp + 1) = t;
 368 #endif
 369       }
 370    }
 371 }
 372 #endif
 373 #endif
 374 
 375 #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
 376 static PNG_CONST png_byte onebppswaptable[256] = {
 377    0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
 378    0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
 379    0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
 380    0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
 381    0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4,
 382    0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
 383    0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
 384    0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
 385    0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2,
 386    0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
 387    0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
 388    0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
 389    0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6,
 390    0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
 391    0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE,
 392    0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
 393    0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1,
 394    0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
 395    0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9,
 396    0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
 397    0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
 398    0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
 399    0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED,
 400    0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
 401    0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3,
 402    0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
 403    0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB,
 404    0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
 405    0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7,
 406    0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
 407    0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF,
 408    0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
 409 };
 410 
 411 static PNG_CONST png_byte twobppswaptable[256] = {
 412    0x00, 0x40, 0x80, 0xC0, 0x10, 0x50, 0x90, 0xD0,
 413    0x20, 0x60, 0xA0, 0xE0, 0x30, 0x70, 0xB0, 0xF0,
 414    0x04, 0x44, 0x84, 0xC4, 0x14, 0x54, 0x94, 0xD4,
 415    0x24, 0x64, 0xA4, 0xE4, 0x34, 0x74, 0xB4, 0xF4,
 416    0x08, 0x48, 0x88, 0xC8, 0x18, 0x58, 0x98, 0xD8,
 417    0x28, 0x68, 0xA8, 0xE8, 0x38, 0x78, 0xB8, 0xF8,
 418    0x0C, 0x4C, 0x8C, 0xCC, 0x1C, 0x5C, 0x9C, 0xDC,
 419    0x2C, 0x6C, 0xAC, 0xEC, 0x3C, 0x7C, 0xBC, 0xFC,
 420    0x01, 0x41, 0x81, 0xC1, 0x11, 0x51, 0x91, 0xD1,
 421    0x21, 0x61, 0xA1, 0xE1, 0x31, 0x71, 0xB1, 0xF1,
 422    0x05, 0x45, 0x85, 0xC5, 0x15, 0x55, 0x95, 0xD5,
 423    0x25, 0x65, 0xA5, 0xE5, 0x35, 0x75, 0xB5, 0xF5,
 424    0x09, 0x49, 0x89, 0xC9, 0x19, 0x59, 0x99, 0xD9,
 425    0x29, 0x69, 0xA9, 0xE9, 0x39, 0x79, 0xB9, 0xF9,
 426    0x0D, 0x4D, 0x8D, 0xCD, 0x1D, 0x5D, 0x9D, 0xDD,
 427    0x2D, 0x6D, 0xAD, 0xED, 0x3D, 0x7D, 0xBD, 0xFD,
 428    0x02, 0x42, 0x82, 0xC2, 0x12, 0x52, 0x92, 0xD2,
 429    0x22, 0x62, 0xA2, 0xE2, 0x32, 0x72, 0xB2, 0xF2,
 430    0x06, 0x46, 0x86, 0xC6, 0x16, 0x56, 0x96, 0xD6,
 431    0x26, 0x66, 0xA6, 0xE6, 0x36, 0x76, 0xB6, 0xF6,
 432    0x0A, 0x4A, 0x8A, 0xCA, 0x1A, 0x5A, 0x9A, 0xDA,
 433    0x2A, 0x6A, 0xAA, 0xEA, 0x3A, 0x7A, 0xBA, 0xFA,
 434    0x0E, 0x4E, 0x8E, 0xCE, 0x1E, 0x5E, 0x9E, 0xDE,
 435    0x2E, 0x6E, 0xAE, 0xEE, 0x3E, 0x7E, 0xBE, 0xFE,
 436    0x03, 0x43, 0x83, 0xC3, 0x13, 0x53, 0x93, 0xD3,
 437    0x23, 0x63, 0xA3, 0xE3, 0x33, 0x73, 0xB3, 0xF3,
 438    0x07, 0x47, 0x87, 0xC7, 0x17, 0x57, 0x97, 0xD7,
 439    0x27, 0x67, 0xA7, 0xE7, 0x37, 0x77, 0xB7, 0xF7,
 440    0x0B, 0x4B, 0x8B, 0xCB, 0x1B, 0x5B, 0x9B, 0xDB,
 441    0x2B, 0x6B, 0xAB, 0xEB, 0x3B, 0x7B, 0xBB, 0xFB,
 442    0x0F, 0x4F, 0x8F, 0xCF, 0x1F, 0x5F, 0x9F, 0xDF,
 443    0x2F, 0x6F, 0xAF, 0xEF, 0x3F, 0x7F, 0xBF, 0xFF
 444 };
 445 
 446 static PNG_CONST png_byte fourbppswaptable[256] = {
 447    0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70,
 448    0x80, 0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0,
 449    0x01, 0x11, 0x21, 0x31, 0x41, 0x51, 0x61, 0x71,
 450    0x81, 0x91, 0xA1, 0xB1, 0xC1, 0xD1, 0xE1, 0xF1,
 451    0x02, 0x12, 0x22, 0x32, 0x42, 0x52, 0x62, 0x72,
 452    0x82, 0x92, 0xA2, 0xB2, 0xC2, 0xD2, 0xE2, 0xF2,
 453    0x03, 0x13, 0x23, 0x33, 0x43, 0x53, 0x63, 0x73,
 454    0x83, 0x93, 0xA3, 0xB3, 0xC3, 0xD3, 0xE3, 0xF3,
 455    0x04, 0x14, 0x24, 0x34, 0x44, 0x54, 0x64, 0x74,
 456    0x84, 0x94, 0xA4, 0xB4, 0xC4, 0xD4, 0xE4, 0xF4,
 457    0x05, 0x15, 0x25, 0x35, 0x45, 0x55, 0x65, 0x75,
 458    0x85, 0x95, 0xA5, 0xB5, 0xC5, 0xD5, 0xE5, 0xF5,
 459    0x06, 0x16, 0x26, 0x36, 0x46, 0x56, 0x66, 0x76,
 460    0x86, 0x96, 0xA6, 0xB6, 0xC6, 0xD6, 0xE6, 0xF6,
 461    0x07, 0x17, 0x27, 0x37, 0x47, 0x57, 0x67, 0x77,
 462    0x87, 0x97, 0xA7, 0xB7, 0xC7, 0xD7, 0xE7, 0xF7,
 463    0x08, 0x18, 0x28, 0x38, 0x48, 0x58, 0x68, 0x78,
 464    0x88, 0x98, 0xA8, 0xB8, 0xC8, 0xD8, 0xE8, 0xF8,
 465    0x09, 0x19, 0x29, 0x39, 0x49, 0x59, 0x69, 0x79,
 466    0x89, 0x99, 0xA9, 0xB9, 0xC9, 0xD9, 0xE9, 0xF9,
 467    0x0A, 0x1A, 0x2A, 0x3A, 0x4A, 0x5A, 0x6A, 0x7A,
 468    0x8A, 0x9A, 0xAA, 0xBA, 0xCA, 0xDA, 0xEA, 0xFA,
 469    0x0B, 0x1B, 0x2B, 0x3B, 0x4B, 0x5B, 0x6B, 0x7B,
 470    0x8B, 0x9B, 0xAB, 0xBB, 0xCB, 0xDB, 0xEB, 0xFB,
 471    0x0C, 0x1C, 0x2C, 0x3C, 0x4C, 0x5C, 0x6C, 0x7C,
 472    0x8C, 0x9C, 0xAC, 0xBC, 0xCC, 0xDC, 0xEC, 0xFC,
 473    0x0D, 0x1D, 0x2D, 0x3D, 0x4D, 0x5D, 0x6D, 0x7D,
 474    0x8D, 0x9D, 0xAD, 0xBD, 0xCD, 0xDD, 0xED, 0xFD,
 475    0x0E, 0x1E, 0x2E, 0x3E, 0x4E, 0x5E, 0x6E, 0x7E,
 476    0x8E, 0x9E, 0xAE, 0xBE, 0xCE, 0xDE, 0xEE, 0xFE,
 477    0x0F, 0x1F, 0x2F, 0x3F, 0x4F, 0x5F, 0x6F, 0x7F,
 478    0x8F, 0x9F, 0xAF, 0xBF, 0xCF, 0xDF, 0xEF, 0xFF
 479 };
 480 
 481 /* Swaps pixel packing order within bytes */
 482 void /* PRIVATE */
 483 png_do_packswap(png_row_infop row_info, png_bytep row)
 484 {
 485    png_debug(1, "in png_do_packswap");
 486 
 487    if (row_info->bit_depth < 8)
 488    {
 489       png_bytep rp;
 490       png_const_bytep end, table;
 491 
 492       end = row + row_info->rowbytes;
 493 
 494       if (row_info->bit_depth == 1)
 495          table = onebppswaptable;
 496 
 497       else if (row_info->bit_depth == 2)
 498          table = twobppswaptable;
 499 
 500       else if (row_info->bit_depth == 4)
 501          table = fourbppswaptable;
 502 
 503       else
 504          return;
 505 
 506       for (rp = row; rp < end; rp++)
 507          *rp = table[*rp];
 508    }
 509 }
 510 #endif /* PACKSWAP || WRITE_PACKSWAP */
 511 
 512 #if defined(PNG_WRITE_FILLER_SUPPORTED) || \
 513     defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
 514 /* Remove a channel - this used to be 'png_do_strip_filler' but it used a
 515  * somewhat weird combination of flags to determine what to do.  All the calls
 516  * to png_do_strip_filler are changed in 1.5.2 to call this instead with the
 517  * correct arguments.
 518  *
 519  * The routine isn't general - the channel must be the channel at the start or
 520  * end (not in the middle) of each pixel.
 521  */
 522 void /* PRIVATE */
 523 png_do_strip_channel(png_row_infop row_info, png_bytep row, int at_start)
 524 {
 525    png_bytep sp = row; /* source pointer */
 526    png_bytep dp = row; /* destination pointer */
 527    png_bytep ep = row + row_info->rowbytes; /* One beyond end of row */
 528 
 529    /* At the start sp will point to the first byte to copy and dp to where
 530     * it is copied to.  ep always points just beyond the end of the row, so
 531     * the loop simply copies (channels-1) channels until sp reaches ep.
 532     *
 533     * at_start:        0 -- convert AG, XG, ARGB, XRGB, AAGG, XXGG, etc.
 534     *            nonzero -- convert GA, GX, RGBA, RGBX, GGAA, RRGGBBXX, etc.
 535     */
 536 
 537    /* GA, GX, XG cases */
 538    if (row_info->channels == 2)
 539    {
 540       if (row_info->bit_depth == 8)
 541       {
 542          if (at_start != 0) /* Skip initial filler */
 543             ++sp;
 544          else          /* Skip initial channel and, for sp, the filler */
 545             sp += 2, ++dp;
 546 
 547          /* For a 1 pixel wide image there is nothing to do */
 548          while (sp < ep)
 549             *dp++ = *sp, sp += 2;
 550 
 551          row_info->pixel_depth = 8;
 552       }
 553 
 554       else if (row_info->bit_depth == 16)
 555       {
 556          if (at_start != 0) /* Skip initial filler */
 557             sp += 2;
 558          else          /* Skip initial channel and, for sp, the filler */
 559             sp += 4, dp += 2;
 560 
 561          while (sp < ep)
 562             *dp++ = *sp++, *dp++ = *sp, sp += 3;
 563 
 564          row_info->pixel_depth = 16;
 565       }
 566 
 567       else
 568          return; /* bad bit depth */
 569 
 570       row_info->channels = 1;
 571 
 572       /* Finally fix the color type if it records an alpha channel */
 573       if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 574          row_info->color_type = PNG_COLOR_TYPE_GRAY;
 575    }
 576 
 577    /* RGBA, RGBX, XRGB cases */
 578    else if (row_info->channels == 4)
 579    {
 580       if (row_info->bit_depth == 8)
 581       {
 582          if (at_start != 0) /* Skip initial filler */
 583             ++sp;
 584          else          /* Skip initial channels and, for sp, the filler */
 585             sp += 4, dp += 3;
 586 
 587          /* Note that the loop adds 3 to dp and 4 to sp each time. */
 588          while (sp < ep)
 589             *dp++ = *sp++, *dp++ = *sp++, *dp++ = *sp, sp += 2;
 590 
 591          row_info->pixel_depth = 24;
 592       }
 593 
 594       else if (row_info->bit_depth == 16)
 595       {
 596          if (at_start != 0) /* Skip initial filler */
 597             sp += 2;
 598          else          /* Skip initial channels and, for sp, the filler */
 599             sp += 8, dp += 6;
 600 
 601          while (sp < ep)
 602          {
 603             /* Copy 6 bytes, skip 2 */
 604             *dp++ = *sp++, *dp++ = *sp++;
 605             *dp++ = *sp++, *dp++ = *sp++;
 606             *dp++ = *sp++, *dp++ = *sp, sp += 3;
 607          }
 608 
 609          row_info->pixel_depth = 48;
 610       }
 611 
 612       else
 613          return; /* bad bit depth */
 614 
 615       row_info->channels = 3;
 616 
 617       /* Finally fix the color type if it records an alpha channel */
 618       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 619          row_info->color_type = PNG_COLOR_TYPE_RGB;
 620    }
 621 
 622    else
 623       return; /* The filler channel has gone already */
 624 
 625    /* Fix the rowbytes value. */
 626    row_info->rowbytes = (unsigned int)(dp-row);
 627 }
 628 #endif
 629 
 630 #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
 631 /* Swaps red and blue bytes within a pixel */
 632 void /* PRIVATE */
 633 png_do_bgr(png_row_infop row_info, png_bytep row)
 634 {
 635    png_debug(1, "in png_do_bgr");
 636 
 637    if ((row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
 638    {
 639       png_uint_32 row_width = row_info->width;
 640       if (row_info->bit_depth == 8)
 641       {
 642          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 643          {
 644             png_bytep rp;
 645             png_uint_32 i;
 646 
 647             for (i = 0, rp = row; i < row_width; i++, rp += 3)
 648             {
 649                png_byte save = *rp;
 650                *rp = *(rp + 2);
 651                *(rp + 2) = save;
 652             }
 653          }
 654 
 655          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 656          {
 657             png_bytep rp;
 658             png_uint_32 i;
 659 
 660             for (i = 0, rp = row; i < row_width; i++, rp += 4)
 661             {
 662                png_byte save = *rp;
 663                *rp = *(rp + 2);
 664                *(rp + 2) = save;
 665             }
 666          }
 667       }
 668 
 669 #ifdef PNG_16BIT_SUPPORTED
 670       else if (row_info->bit_depth == 16)
 671       {
 672          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 673          {
 674             png_bytep rp;
 675             png_uint_32 i;
 676 
 677             for (i = 0, rp = row; i < row_width; i++, rp += 6)
 678             {
 679                png_byte save = *rp;
 680                *rp = *(rp + 4);
 681                *(rp + 4) = save;
 682                save = *(rp + 1);
 683                *(rp + 1) = *(rp + 5);
 684                *(rp + 5) = save;
 685             }
 686          }
 687 
 688          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 689          {
 690             png_bytep rp;
 691             png_uint_32 i;
 692 
 693             for (i = 0, rp = row; i < row_width; i++, rp += 8)
 694             {
 695                png_byte save = *rp;
 696                *rp = *(rp + 4);
 697                *(rp + 4) = save;
 698                save = *(rp + 1);
 699                *(rp + 1) = *(rp + 5);
 700                *(rp + 5) = save;
 701             }
 702          }
 703       }
 704 #endif
 705    }
 706 }
 707 #endif /* READ_BGR || WRITE_BGR */
 708 
 709 #if defined(PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED) || \
 710     defined(PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED)
 711 /* Added at libpng-1.5.10 */
 712 void /* PRIVATE */
 713 png_do_check_palette_indexes(png_structrp png_ptr, png_row_infop row_info)
 714 {
 715    if (png_ptr->num_palette < (1 << row_info->bit_depth) &&
 716       png_ptr->num_palette > 0) /* num_palette can be 0 in MNG files */
 717    {
 718       /* Calculations moved outside switch in an attempt to stop different
 719        * compiler warnings.  'padding' is in *bits* within the last byte, it is
 720        * an 'int' because pixel_depth becomes an 'int' in the expression below,
 721        * and this calculation is used because it avoids warnings that other
 722        * forms produced on either GCC or MSVC.
 723        */
 724       int padding = PNG_PADBITS(row_info->pixel_depth, row_info->width);
 725       png_bytep rp = png_ptr->row_buf + row_info->rowbytes;
 726 
 727       switch (row_info->bit_depth)
 728       {
 729          case 1:
 730          {
 731             /* in this case, all bytes must be 0 so we don't need
 732              * to unpack the pixels except for the rightmost one.
 733              */
 734             for (; rp > png_ptr->row_buf; rp--)
 735             {
 736               if ((*rp >> padding) != 0)
 737                  png_ptr->num_palette_max = 1;
 738               padding = 0;
 739             }
 740 
 741             break;
 742          }
 743 
 744          case 2:
 745          {
 746             for (; rp > png_ptr->row_buf; rp--)
 747             {
 748               int i = ((*rp >> padding) & 0x03);
 749 
 750               if (i > png_ptr->num_palette_max)
 751                  png_ptr->num_palette_max = i;
 752 
 753               i = (((*rp >> padding) >> 2) & 0x03);
 754 
 755               if (i > png_ptr->num_palette_max)
 756                  png_ptr->num_palette_max = i;
 757 
 758               i = (((*rp >> padding) >> 4) & 0x03);
 759 
 760               if (i > png_ptr->num_palette_max)
 761                  png_ptr->num_palette_max = i;
 762 
 763               i = (((*rp >> padding) >> 6) & 0x03);
 764 
 765               if (i > png_ptr->num_palette_max)
 766                  png_ptr->num_palette_max = i;
 767 
 768               padding = 0;
 769             }
 770 
 771             break;
 772          }
 773 
 774          case 4:
 775          {
 776             for (; rp > png_ptr->row_buf; rp--)
 777             {
 778               int i = ((*rp >> padding) & 0x0f);
 779 
 780               if (i > png_ptr->num_palette_max)
 781                  png_ptr->num_palette_max = i;
 782 
 783               i = (((*rp >> padding) >> 4) & 0x0f);
 784 
 785               if (i > png_ptr->num_palette_max)
 786                  png_ptr->num_palette_max = i;
 787 
 788               padding = 0;
 789             }
 790 
 791             break;
 792          }
 793 
 794          case 8:
 795          {
 796             for (; rp > png_ptr->row_buf; rp--)
 797             {
 798                if (*rp > png_ptr->num_palette_max)
 799                   png_ptr->num_palette_max = (int) *rp;
 800             }
 801 
 802             break;
 803          }
 804 
 805          default:
 806             break;
 807       }
 808    }
 809 }
 810 #endif /* CHECK_FOR_INVALID_INDEX */
 811 
 812 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
 813     defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
 814 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
 815 void PNGAPI
 816 png_set_user_transform_info(png_structrp png_ptr, png_voidp
 817    user_transform_ptr, int user_transform_depth, int user_transform_channels)
 818 {
 819    png_debug(1, "in png_set_user_transform_info");
 820 
 821    if (png_ptr == NULL)
 822       return;
 823 
 824 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
 825    if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
 826       (png_ptr->flags & PNG_FLAG_ROW_INIT) != 0)
 827    {
 828       png_app_error(png_ptr,
 829           "info change after png_start_read_image or png_read_update_info");
 830       return;
 831    }
 832 #endif
 833 
 834    png_ptr->user_transform_ptr = user_transform_ptr;
 835    png_ptr->user_transform_depth = (png_byte)user_transform_depth;
 836    png_ptr->user_transform_channels = (png_byte)user_transform_channels;
 837 }
 838 #endif
 839 
 840 /* This function returns a pointer to the user_transform_ptr associated with
 841  * the user transform functions.  The application should free any memory
 842  * associated with this pointer before png_write_destroy and png_read_destroy
 843  * are called.
 844  */
 845 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
 846 png_voidp PNGAPI
 847 png_get_user_transform_ptr(png_const_structrp png_ptr)
 848 {
 849    if (png_ptr == NULL)
 850       return (NULL);
 851 
 852    return png_ptr->user_transform_ptr;
 853 }
 854 #endif
 855 
 856 #ifdef PNG_USER_TRANSFORM_INFO_SUPPORTED
 857 png_uint_32 PNGAPI
 858 png_get_current_row_number(png_const_structrp png_ptr)
 859 {
 860    /* See the comments in png.h - this is the sub-image row when reading an
 861     * interlaced image.
 862     */
 863    if (png_ptr != NULL)
 864       return png_ptr->row_number;
 865 
 866    return PNG_UINT_32_MAX; /* help the app not to fail silently */
 867 }
 868 
 869 png_byte PNGAPI
 870 png_get_current_pass_number(png_const_structrp png_ptr)
 871 {
 872    if (png_ptr != NULL)
 873       return png_ptr->pass;
 874    return 8; /* invalid */
 875 }
 876 #endif /* USER_TRANSFORM_INFO */
 877 #endif /* READ_USER_TRANSFORM || WRITE_USER_TRANSFORM */
 878 #endif /* READ || WRITE */