pngwtran.c

   1
   2 /* pngwtran.c - transforms the data in a row for PNG writers
   3  *
   4  * Last changed in libpng 1.5.0 [January 6, 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 #ifdef PNG_WRITE_SUPPORTED
  17
  18 /* Transform the data according to the user's wishes.  The order of
  19  * transformations is significant.
  20  */
  21 void /* PRIVATE */
  22 png_do_write_transformations(png_structp png_ptr)
  23 {
  24    png_debug(1, "in png_do_write_transformations");
  25
  26    if (png_ptr == NULL)
  27       return;
  28
  29 #ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
  30    if (png_ptr->transformations & PNG_USER_TRANSFORM)
  31       if (png_ptr->write_user_transform_fn != NULL)
  32          (*(png_ptr->write_user_transform_fn)) /* User write transform
  33                                                  function */
  34              (png_ptr,                    /* png_ptr */
  35              &(png_ptr->row_info),           /* row_info: */
  36                 /*  png_uint_32 width;       width of row */
  37                 /*  png_size_t rowbytes;     number of bytes in row */
  38                 /*  png_byte color_type;     color type of pixels */
  39                 /*  png_byte bit_depth;      bit depth of samples */
  40                 /*  png_byte channels;       number of channels (1-4) */
  41                 /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
  42              png_ptr->row_buf + 1);      /* start of pixel data for row */
  43 #endif
  44
  45 #ifdef PNG_WRITE_FILLER_SUPPORTED
  46    if (png_ptr->transformations & PNG_FILLER)
  47       png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
  48           png_ptr->flags);
  49 #endif
  50
  51 #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
  52    if (png_ptr->transformations & PNG_PACKSWAP)
  53       png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
  54 #endif
  55
  56 #ifdef PNG_WRITE_PACK_SUPPORTED
  57    if (png_ptr->transformations & PNG_PACK)
  58       png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
  59           (png_uint_32)png_ptr->bit_depth);
  60 #endif
  61
  62 #ifdef PNG_WRITE_SWAP_SUPPORTED
  63    if (png_ptr->transformations & PNG_SWAP_BYTES)
  64       png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
  65 #endif
  66
  67 #ifdef PNG_WRITE_SHIFT_SUPPORTED
  68    if (png_ptr->transformations & PNG_SHIFT)
  69       png_do_shift(&(png_ptr->row_info), png_ptr->row_buf + 1,
  70           &(png_ptr->shift));
  71 #endif
  72
  73 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
  74    if (png_ptr->transformations & PNG_SWAP_ALPHA)
  75       png_do_write_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
  76 #endif
  77
  78 #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
  79    if (png_ptr->transformations & PNG_INVERT_ALPHA)
  80       png_do_write_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
  81 #endif
  82
  83 #ifdef PNG_WRITE_BGR_SUPPORTED
  84    if (png_ptr->transformations & PNG_BGR)
  85       png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
  86 #endif
  87
  88 #ifdef PNG_WRITE_INVERT_SUPPORTED
  89    if (png_ptr->transformations & PNG_INVERT_MONO)
  90       png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
  91 #endif
  92 }
  93
  94 #ifdef PNG_WRITE_PACK_SUPPORTED
  95 /* Pack pixels into bytes.  Pass the true bit depth in bit_depth.  The
  96  * row_info bit depth should be 8 (one pixel per byte).  The channels
  97  * should be 1 (this only happens on grayscale and paletted images).
  98  */
  99 void /* PRIVATE */
 100 png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
 101 {
 102    png_debug(1, "in png_do_pack");
 103
 104    if (row_info->bit_depth == 8 &&
 105       row_info->channels == 1)
 106    {
 107       switch ((int)bit_depth)
 108       {
 109          case 1:
 110          {
 111             png_bytep sp, dp;
 112             int mask, v;
 113             png_uint_32 i;
 114             png_uint_32 row_width = row_info->width;
 115
 116             sp = row;
 117             dp = row;
 118             mask = 0x80;
 119             v = 0;
 120
 121             for (i = 0; i < row_width; i++)
 122             {
 123                if (*sp != 0)
 124                   v |= mask;
 125
 126                sp++;
 127
 128                if (mask > 1)
 129                   mask >>= 1;
 130
 131                else
 132                {
 133                   mask = 0x80;
 134                   *dp = (png_byte)v;
 135                   dp++;
 136                   v = 0;
 137                }
 138             }
 139
 140             if (mask != 0x80)
 141                *dp = (png_byte)v;
 142
 143             break;
 144          }
 145
 146          case 2:
 147          {
 148             png_bytep sp, dp;
 149             int shift, v;
 150             png_uint_32 i;
 151             png_uint_32 row_width = row_info->width;
 152
 153             sp = row;
 154             dp = row;
 155             shift = 6;
 156             v = 0;
 157
 158             for (i = 0; i < row_width; i++)
 159             {
 160                png_byte value;
 161
 162                value = (png_byte)(*sp & 0x03);
 163                v |= (value << shift);
 164
 165                if (shift == 0)
 166                {
 167                   shift = 6;
 168                   *dp = (png_byte)v;
 169                   dp++;
 170                   v = 0;
 171                }
 172
 173                else
 174                   shift -= 2;
 175
 176                sp++;
 177             }
 178
 179             if (shift != 6)
 180                *dp = (png_byte)v;
 181
 182             break;
 183          }
 184
 185          case 4:
 186          {
 187             png_bytep sp, dp;
 188             int shift, v;
 189             png_uint_32 i;
 190             png_uint_32 row_width = row_info->width;
 191
 192             sp = row;
 193             dp = row;
 194             shift = 4;
 195             v = 0;
 196
 197             for (i = 0; i < row_width; i++)
 198             {
 199                png_byte value;
 200
 201                value = (png_byte)(*sp & 0x0f);
 202                v |= (value << shift);
 203
 204                if (shift == 0)
 205                {
 206                   shift = 4;
 207                   *dp = (png_byte)v;
 208                   dp++;
 209                   v = 0;
 210                }
 211
 212                else
 213                   shift -= 4;
 214
 215                sp++;
 216             }
 217
 218             if (shift != 4)
 219                *dp = (png_byte)v;
 220
 221             break;
 222          }
 223
 224          default:
 225             break;
 226       }
 227
 228       row_info->bit_depth = (png_byte)bit_depth;
 229       row_info->pixel_depth = (png_byte)(bit_depth * row_info->channels);
 230       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
 231           row_info->width);
 232    }
 233 }
 234 #endif
 235
 236 #ifdef PNG_WRITE_SHIFT_SUPPORTED
 237 /* Shift pixel values to take advantage of whole range.  Pass the
 238  * true number of bits in bit_depth.  The row should be packed
 239  * according to row_info->bit_depth.  Thus, if you had a row of
 240  * bit depth 4, but the pixels only had values from 0 to 7, you
 241  * would pass 3 as bit_depth, and this routine would translate the
 242  * data to 0 to 15.
 243  */
 244 void /* PRIVATE */
 245 png_do_shift(png_row_infop row_info, png_bytep row,
 246     png_const_color_8p bit_depth)
 247 {
 248    png_debug(1, "in png_do_shift");
 249
 250    if (row_info->color_type != PNG_COLOR_TYPE_PALETTE)
 251    {
 252       int shift_start[4], shift_dec[4];
 253       int channels = 0;
 254
 255       if (row_info->color_type & PNG_COLOR_MASK_COLOR)
 256       {
 257          shift_start[channels] = row_info->bit_depth - bit_depth->red;
 258          shift_dec[channels] = bit_depth->red;
 259          channels++;
 260
 261          shift_start[channels] = row_info->bit_depth - bit_depth->green;
 262          shift_dec[channels] = bit_depth->green;
 263          channels++;
 264
 265          shift_start[channels] = row_info->bit_depth - bit_depth->blue;
 266          shift_dec[channels] = bit_depth->blue;
 267          channels++;
 268       }
 269
 270       else
 271       {
 272          shift_start[channels] = row_info->bit_depth - bit_depth->gray;
 273          shift_dec[channels] = bit_depth->gray;
 274          channels++;
 275       }
 276
 277       if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
 278       {
 279          shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
 280          shift_dec[channels] = bit_depth->alpha;
 281          channels++;
 282       }
 283
 284       /* With low row depths, could only be grayscale, so one channel */
 285       if (row_info->bit_depth < 8)
 286       {
 287          png_bytep bp = row;
 288          png_size_t i;
 289          png_byte mask;
 290          png_size_t row_bytes = row_info->rowbytes;
 291
 292          if (bit_depth->gray == 1 && row_info->bit_depth == 2)
 293             mask = 0x55;
 294
 295          else if (row_info->bit_depth == 4 && bit_depth->gray == 3)
 296             mask = 0x11;
 297
 298          else
 299             mask = 0xff;
 300
 301          for (i = 0; i < row_bytes; i++, bp++)
 302          {
 303             png_uint_16 v;
 304             int j;
 305
 306             v = *bp;
 307             *bp = 0;
 308
 309             for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
 310             {
 311                if (j > 0)
 312                   *bp |= (png_byte)((v << j) & 0xff);
 313
 314                else
 315                   *bp |= (png_byte)((v >> (-j)) & mask);
 316             }
 317          }
 318       }
 319
 320       else if (row_info->bit_depth == 8)
 321       {
 322          png_bytep bp = row;
 323          png_uint_32 i;
 324          png_uint_32 istop = channels * row_info->width;
 325
 326          for (i = 0; i < istop; i++, bp++)
 327          {
 328
 329             png_uint_16 v;
 330             int j;
 331             int c = (int)(i%channels);
 332
 333             v = *bp;
 334             *bp = 0;
 335
 336             for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
 337             {
 338                if (j > 0)
 339                   *bp |= (png_byte)((v << j) & 0xff);
 340
 341                else
 342                   *bp |= (png_byte)((v >> (-j)) & 0xff);
 343             }
 344          }
 345       }
 346
 347       else
 348       {
 349          png_bytep bp;
 350          png_uint_32 i;
 351          png_uint_32 istop = channels * row_info->width;
 352
 353          for (bp = row, i = 0; i < istop; i++)
 354          {
 355             int c = (int)(i%channels);
 356             png_uint_16 value, v;
 357             int j;
 358
 359             v = (png_uint_16)(((png_uint_16)(*bp) << 8) + *(bp + 1));
 360             value = 0;
 361
 362             for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
 363             {
 364                if (j > 0)
 365                   value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
 366
 367                else
 368                   value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
 369             }
 370             *bp++ = (png_byte)(value >> 8);
 371             *bp++ = (png_byte)(value & 0xff);
 372          }
 373       }
 374    }
 375 }
 376 #endif
 377
 378 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
 379 void /* PRIVATE */
 380 png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
 381 {
 382    png_debug(1, "in png_do_write_swap_alpha");
 383
 384    {
 385       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 386       {
 387          if (row_info->bit_depth == 8)
 388          {
 389             /* This converts from ARGB to RGBA */
 390             png_bytep sp, dp;
 391             png_uint_32 i;
 392             png_uint_32 row_width = row_info->width;
 393
 394             for (i = 0, sp = dp = row; i < row_width; i++)
 395             {
 396                png_byte save = *(sp++);
 397                *(dp++) = *(sp++);
 398                *(dp++) = *(sp++);
 399                *(dp++) = *(sp++);
 400                *(dp++) = save;
 401             }
 402          }
 403
 404 #ifdef PNG_WRITE_16BIT_SUPPORTED
 405          else
 406          {
 407             /* This converts from AARRGGBB to RRGGBBAA */
 408             png_bytep sp, dp;
 409             png_uint_32 i;
 410             png_uint_32 row_width = row_info->width;
 411
 412             for (i = 0, sp = dp = row; i < row_width; i++)
 413             {
 414                png_byte save[2];
 415                save[0] = *(sp++);
 416                save[1] = *(sp++);
 417                *(dp++) = *(sp++);
 418                *(dp++) = *(sp++);
 419                *(dp++) = *(sp++);
 420                *(dp++) = *(sp++);
 421                *(dp++) = *(sp++);
 422                *(dp++) = *(sp++);
 423                *(dp++) = save[0];
 424                *(dp++) = save[1];
 425             }
 426          }
 427 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 428       }
 429
 430       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 431       {
 432          if (row_info->bit_depth == 8)
 433          {
 434             /* This converts from AG to GA */
 435             png_bytep sp, dp;
 436             png_uint_32 i;
 437             png_uint_32 row_width = row_info->width;
 438
 439             for (i = 0, sp = dp = row; i < row_width; i++)
 440             {
 441                png_byte save = *(sp++);
 442                *(dp++) = *(sp++);
 443                *(dp++) = save;
 444             }
 445          }
 446
 447 #ifdef PNG_WRITE_16BIT_SUPPORTED
 448          else
 449          {
 450             /* This converts from AAGG to GGAA */
 451             png_bytep sp, dp;
 452             png_uint_32 i;
 453             png_uint_32 row_width = row_info->width;
 454
 455             for (i = 0, sp = dp = row; i < row_width; i++)
 456             {
 457                png_byte save[2];
 458                save[0] = *(sp++);
 459                save[1] = *(sp++);
 460                *(dp++) = *(sp++);
 461                *(dp++) = *(sp++);
 462                *(dp++) = save[0];
 463                *(dp++) = save[1];
 464             }
 465          }
 466 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 467       }
 468    }
 469 }
 470 #endif
 471
 472 #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
 473 void /* PRIVATE */
 474 png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
 475 {
 476    png_debug(1, "in png_do_write_invert_alpha");
 477
 478    {
 479       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 480       {
 481          if (row_info->bit_depth == 8)
 482          {
 483             /* This inverts the alpha channel in RGBA */
 484             png_bytep sp, dp;
 485             png_uint_32 i;
 486             png_uint_32 row_width = row_info->width;
 487
 488             for (i = 0, sp = dp = row; i < row_width; i++)
 489             {
 490                /* Does nothing
 491                *(dp++) = *(sp++);
 492                *(dp++) = *(sp++);
 493                *(dp++) = *(sp++);
 494                */
 495                sp+=3; dp = sp;
 496                *(dp++) = (png_byte)(255 - *(sp++));
 497             }
 498          }
 499
 500 #ifdef PNG_WRITE_16BIT_SUPPORTED
 501          else
 502          {
 503             /* This inverts the alpha channel in RRGGBBAA */
 504             png_bytep sp, dp;
 505             png_uint_32 i;
 506             png_uint_32 row_width = row_info->width;
 507
 508             for (i = 0, sp = dp = row; i < row_width; i++)
 509             {
 510                /* Does nothing
 511                *(dp++) = *(sp++);
 512                *(dp++) = *(sp++);
 513                *(dp++) = *(sp++);
 514                *(dp++) = *(sp++);
 515                *(dp++) = *(sp++);
 516                *(dp++) = *(sp++);
 517                */
 518                sp+=6; dp = sp;
 519                *(dp++) = (png_byte)(255 - *(sp++));
 520                *(dp++) = (png_byte)(255 - *(sp++));
 521             }
 522          }
 523 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 524       }
 525
 526       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 527       {
 528          if (row_info->bit_depth == 8)
 529          {
 530             /* This inverts the alpha channel in GA */
 531             png_bytep sp, dp;
 532             png_uint_32 i;
 533             png_uint_32 row_width = row_info->width;
 534
 535             for (i = 0, sp = dp = row; i < row_width; i++)
 536             {
 537                *(dp++) = *(sp++);
 538                *(dp++) = (png_byte)(255 - *(sp++));
 539             }
 540          }
 541
 542 #ifdef PNG_WRITE_16BIT_SUPPORTED
 543          else
 544          {
 545             /* This inverts the alpha channel in GGAA */
 546             png_bytep sp, dp;
 547             png_uint_32 i;
 548             png_uint_32 row_width = row_info->width;
 549
 550             for (i = 0, sp = dp = row; i < row_width; i++)
 551             {
 552                /* Does nothing
 553                *(dp++) = *(sp++);
 554                *(dp++) = *(sp++);
 555                */
 556                sp+=2; dp = sp;
 557                *(dp++) = (png_byte)(255 - *(sp++));
 558                *(dp++) = (png_byte)(255 - *(sp++));
 559             }
 560          }
 561 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 562       }
 563    }
 564 }
 565 #endif
 566
 567 #ifdef PNG_MNG_FEATURES_SUPPORTED
 568 /* Undoes intrapixel differencing  */
 569 void /* PRIVATE */
 570 png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
 571 {
 572    png_debug(1, "in png_do_write_intrapixel");
 573
 574    if ((row_info->color_type & PNG_COLOR_MASK_COLOR))
 575    {
 576       int bytes_per_pixel;
 577       png_uint_32 row_width = row_info->width;
 578       if (row_info->bit_depth == 8)
 579       {
 580          png_bytep rp;
 581          png_uint_32 i;
 582
 583          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 584             bytes_per_pixel = 3;
 585
 586          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 587             bytes_per_pixel = 4;
 588
 589          else
 590             return;
 591
 592          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
 593          {
 594             *(rp)     = (png_byte)((*rp       - *(rp + 1)) & 0xff);
 595             *(rp + 2) = (png_byte)((*(rp + 2) - *(rp + 1)) & 0xff);
 596          }
 597       }
 598
 599 #ifdef PNG_WRITE_16BIT_SUPPORTED
 600       else if (row_info->bit_depth == 16)
 601       {
 602          png_bytep rp;
 603          png_uint_32 i;
 604
 605          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 606             bytes_per_pixel = 6;
 607
 608          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 609             bytes_per_pixel = 8;
 610
 611          else
 612             return;
 613
 614          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
 615          {
 616             png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);
 617             png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);
 618             png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);
 619             png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);
 620             png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
 621             *(rp    ) = (png_byte)((red >> 8) & 0xff);
 622             *(rp + 1) = (png_byte)(red & 0xff);
 623             *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
 624             *(rp + 5) = (png_byte)(blue & 0xff);
 625          }
 626       }
 627 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 628    }
 629 }
 630 #endif /* PNG_MNG_FEATURES_SUPPORTED */
 631 #endif /* PNG_WRITE_SUPPORTED */