src/png/pngwtran.c

   1
   2 /* pngwtran.c - transforms the data in a row for PNG writers
   3  *
   4  * Last changed in libpng 1.6.0 [February 14, 2013]
   5  * Copyright (c) 1998-2013 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 #ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
  19 /* Transform the data according to the user's wishes.  The order of
  20  * transformations is significant.
  21  */
  22 void /* PRIVATE */
  23 png_do_write_transformations(png_structrp png_ptr, png_row_infop row_info)
  24 {
  25    png_debug(1, "in png_do_write_transformations");
  26
  27    if (png_ptr == NULL)
  28       return;
  29
  30 #ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
  31    if (png_ptr->transformations & PNG_USER_TRANSFORM)
  32       if (png_ptr->write_user_transform_fn != NULL)
  33          (*(png_ptr->write_user_transform_fn)) /* User write transform
  34                                                  function */
  35              (png_ptr,  /* png_ptr */
  36              row_info,  /* row_info: */
  37                 /*  png_uint_32 width;       width of row */
  38                 /*  png_size_t rowbytes;     number of bytes in row */
  39                 /*  png_byte color_type;     color type of pixels */
  40                 /*  png_byte bit_depth;      bit depth of samples */
  41                 /*  png_byte channels;       number of channels (1-4) */
  42                 /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
  43              png_ptr->row_buf + 1);      /* start of pixel data for row */
  44 #endif
  45
  46 #ifdef PNG_WRITE_FILLER_SUPPORTED
  47    if (png_ptr->transformations & PNG_FILLER)
  48       png_do_strip_channel(row_info, png_ptr->row_buf + 1,
  49          !(png_ptr->flags & PNG_FLAG_FILLER_AFTER));
  50 #endif
  51
  52 #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
  53    if (png_ptr->transformations & PNG_PACKSWAP)
  54       png_do_packswap(row_info, png_ptr->row_buf + 1);
  55 #endif
  56
  57 #ifdef PNG_WRITE_PACK_SUPPORTED
  58    if (png_ptr->transformations & PNG_PACK)
  59       png_do_pack(row_info, png_ptr->row_buf + 1,
  60           (png_uint_32)png_ptr->bit_depth);
  61 #endif
  62
  63 #ifdef PNG_WRITE_SWAP_SUPPORTED
  64    if (png_ptr->transformations & PNG_SWAP_BYTES)
  65       png_do_swap(row_info, png_ptr->row_buf + 1);
  66 #endif
  67
  68 #ifdef PNG_WRITE_SHIFT_SUPPORTED
  69    if (png_ptr->transformations & PNG_SHIFT)
  70       png_do_shift(row_info, png_ptr->row_buf + 1,
  71           &(png_ptr->shift));
  72 #endif
  73
  74 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
  75    if (png_ptr->transformations & PNG_SWAP_ALPHA)
  76       png_do_write_swap_alpha(row_info, png_ptr->row_buf + 1);
  77 #endif
  78
  79 #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
  80    if (png_ptr->transformations & PNG_INVERT_ALPHA)
  81       png_do_write_invert_alpha(row_info, png_ptr->row_buf + 1);
  82 #endif
  83
  84 #ifdef PNG_WRITE_BGR_SUPPORTED
  85    if (png_ptr->transformations & PNG_BGR)
  86       png_do_bgr(row_info, png_ptr->row_buf + 1);
  87 #endif
  88
  89 #ifdef PNG_WRITE_INVERT_SUPPORTED
  90    if (png_ptr->transformations & PNG_INVERT_MONO)
  91       png_do_invert(row_info, png_ptr->row_buf + 1);
  92 #endif
  93 }
  94
  95 #ifdef PNG_WRITE_PACK_SUPPORTED
  96 /* Pack pixels into bytes.  Pass the true bit depth in bit_depth.  The
  97  * row_info bit depth should be 8 (one pixel per byte).  The channels
  98  * should be 1 (this only happens on grayscale and paletted images).
  99  */
 100 void /* PRIVATE */
 101 png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
 102 {
 103    png_debug(1, "in png_do_pack");
 104
 105    if (row_info->bit_depth == 8 &&
 106       row_info->channels == 1)
 107    {
 108       switch ((int)bit_depth)
 109       {
 110          case 1:
 111          {
 112             png_bytep sp, dp;
 113             int mask, v;
 114             png_uint_32 i;
 115             png_uint_32 row_width = row_info->width;
 116
 117             sp = row;
 118             dp = row;
 119             mask = 0x80;
 120             v = 0;
 121
 122             for (i = 0; i < row_width; i++)
 123             {
 124                if (*sp != 0)
 125                   v |= mask;
 126
 127                sp++;
 128
 129                if (mask > 1)
 130                   mask >>= 1;
 131
 132                else
 133                {
 134                   mask = 0x80;
 135                   *dp = (png_byte)v;
 136                   dp++;
 137                   v = 0;
 138                }
 139             }
 140
 141             if (mask != 0x80)
 142                *dp = (png_byte)v;
 143
 144             break;
 145          }
 146
 147          case 2:
 148          {
 149             png_bytep sp, dp;
 150             int shift, v;
 151             png_uint_32 i;
 152             png_uint_32 row_width = row_info->width;
 153
 154             sp = row;
 155             dp = row;
 156             shift = 6;
 157             v = 0;
 158
 159             for (i = 0; i < row_width; i++)
 160             {
 161                png_byte value;
 162
 163                value = (png_byte)(*sp & 0x03);
 164                v |= (value << shift);
 165
 166                if (shift == 0)
 167                {
 168                   shift = 6;
 169                   *dp = (png_byte)v;
 170                   dp++;
 171                   v = 0;
 172                }
 173
 174                else
 175                   shift -= 2;
 176
 177                sp++;
 178             }
 179
 180             if (shift != 6)
 181                *dp = (png_byte)v;
 182
 183             break;
 184          }
 185
 186          case 4:
 187          {
 188             png_bytep sp, dp;
 189             int shift, v;
 190             png_uint_32 i;
 191             png_uint_32 row_width = row_info->width;
 192
 193             sp = row;
 194             dp = row;
 195             shift = 4;
 196             v = 0;
 197
 198             for (i = 0; i < row_width; i++)
 199             {
 200                png_byte value;
 201
 202                value = (png_byte)(*sp & 0x0f);
 203                v |= (value << shift);
 204
 205                if (shift == 0)
 206                {
 207                   shift = 4;
 208                   *dp = (png_byte)v;
 209                   dp++;
 210                   v = 0;
 211                }
 212
 213                else
 214                   shift -= 4;
 215
 216                sp++;
 217             }
 218
 219             if (shift != 4)
 220                *dp = (png_byte)v;
 221
 222             break;
 223          }
 224
 225          default:
 226             break;
 227       }
 228
 229       row_info->bit_depth = (png_byte)bit_depth;
 230       row_info->pixel_depth = (png_byte)(bit_depth * row_info->channels);
 231       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
 232           row_info->width);
 233    }
 234 }
 235 #endif
 236
 237 #ifdef PNG_WRITE_SHIFT_SUPPORTED
 238 /* Shift pixel values to take advantage of whole range.  Pass the
 239  * true number of bits in bit_depth.  The row should be packed
 240  * according to row_info->bit_depth.  Thus, if you had a row of
 241  * bit depth 4, but the pixels only had values from 0 to 7, you
 242  * would pass 3 as bit_depth, and this routine would translate the
 243  * data to 0 to 15.
 244  */
 245 void /* PRIVATE */
 246 png_do_shift(png_row_infop row_info, png_bytep row,
 247     png_const_color_8p bit_depth)
 248 {
 249    png_debug(1, "in png_do_shift");
 250
 251    if (row_info->color_type != PNG_COLOR_TYPE_PALETTE)
 252    {
 253       int shift_start[4], shift_dec[4];
 254       int channels = 0;
 255
 256       if (row_info->color_type & PNG_COLOR_MASK_COLOR)
 257       {
 258          shift_start[channels] = row_info->bit_depth - bit_depth->red;
 259          shift_dec[channels] = bit_depth->red;
 260          channels++;
 261
 262          shift_start[channels] = row_info->bit_depth - bit_depth->green;
 263          shift_dec[channels] = bit_depth->green;
 264          channels++;
 265
 266          shift_start[channels] = row_info->bit_depth - bit_depth->blue;
 267          shift_dec[channels] = bit_depth->blue;
 268          channels++;
 269       }
 270
 271       else
 272       {
 273          shift_start[channels] = row_info->bit_depth - bit_depth->gray;
 274          shift_dec[channels] = bit_depth->gray;
 275          channels++;
 276       }
 277
 278       if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
 279       {
 280          shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
 281          shift_dec[channels] = bit_depth->alpha;
 282          channels++;
 283       }
 284
 285       /* With low row depths, could only be grayscale, so one channel */
 286       if (row_info->bit_depth < 8)
 287       {
 288          png_bytep bp = row;
 289          png_size_t i;
 290          unsigned int mask;
 291          png_size_t row_bytes = row_info->rowbytes;
 292
 293          if (bit_depth->gray == 1 && row_info->bit_depth == 2)
 294             mask = 0x55;
 295
 296          else if (row_info->bit_depth == 4 && bit_depth->gray == 3)
 297             mask = 0x11;
 298
 299          else
 300             mask = 0xff;
 301
 302          for (i = 0; i < row_bytes; i++, bp++)
 303          {
 304             int j;
 305             unsigned int v, out;
 306
 307             v = *bp;
 308             out = 0;
 309
 310             for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
 311             {
 312                if (j > 0)
 313                   out |= v << j;
 314
 315                else
 316                   out |= (v >> (-j)) & mask;
 317             }
 318
 319             *bp = (png_byte)(out & 0xff);
 320          }
 321       }
 322
 323       else if (row_info->bit_depth == 8)
 324       {
 325          png_bytep bp = row;
 326          png_uint_32 i;
 327          png_uint_32 istop = channels * row_info->width;
 328
 329          for (i = 0; i < istop; i++, bp++)
 330          {
 331
 332             const unsigned int c = i%channels;
 333             int j;
 334             unsigned int v, out;
 335
 336             v = *bp;
 337             out = 0;
 338
 339             for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
 340             {
 341                if (j > 0)
 342                   out |= v << j;
 343
 344                else
 345                   out |= v >> (-j);
 346             }
 347
 348             *bp = (png_byte)(out & 0xff);
 349          }
 350       }
 351
 352       else
 353       {
 354          png_bytep bp;
 355          png_uint_32 i;
 356          png_uint_32 istop = channels * row_info->width;
 357
 358          for (bp = row, i = 0; i < istop; i++)
 359          {
 360             const unsigned int c = i%channels;
 361             int j;
 362             unsigned int value, v;
 363
 364             v = png_get_uint_16(bp);
 365             value = 0;
 366
 367             for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
 368             {
 369                if (j > 0)
 370                   value |= v << j;
 371
 372                else
 373                   value |= v >> (-j);
 374             }
 375             *bp++ = (png_byte)((value >> 8) & 0xff);
 376             *bp++ = (png_byte)(value & 0xff);
 377          }
 378       }
 379    }
 380 }
 381 #endif
 382
 383 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
 384 void /* PRIVATE */
 385 png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
 386 {
 387    png_debug(1, "in png_do_write_swap_alpha");
 388
 389    {
 390       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 391       {
 392          if (row_info->bit_depth == 8)
 393          {
 394             /* This converts from ARGB to RGBA */
 395             png_bytep sp, dp;
 396             png_uint_32 i;
 397             png_uint_32 row_width = row_info->width;
 398
 399             for (i = 0, sp = dp = row; i < row_width; i++)
 400             {
 401                png_byte save = *(sp++);
 402                *(dp++) = *(sp++);
 403                *(dp++) = *(sp++);
 404                *(dp++) = *(sp++);
 405                *(dp++) = save;
 406             }
 407          }
 408
 409 #ifdef PNG_WRITE_16BIT_SUPPORTED
 410          else
 411          {
 412             /* This converts from AARRGGBB to RRGGBBAA */
 413             png_bytep sp, dp;
 414             png_uint_32 i;
 415             png_uint_32 row_width = row_info->width;
 416
 417             for (i = 0, sp = dp = row; i < row_width; i++)
 418             {
 419                png_byte save[2];
 420                save[0] = *(sp++);
 421                save[1] = *(sp++);
 422                *(dp++) = *(sp++);
 423                *(dp++) = *(sp++);
 424                *(dp++) = *(sp++);
 425                *(dp++) = *(sp++);
 426                *(dp++) = *(sp++);
 427                *(dp++) = *(sp++);
 428                *(dp++) = save[0];
 429                *(dp++) = save[1];
 430             }
 431          }
 432 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 433       }
 434
 435       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 436       {
 437          if (row_info->bit_depth == 8)
 438          {
 439             /* This converts from AG to GA */
 440             png_bytep sp, dp;
 441             png_uint_32 i;
 442             png_uint_32 row_width = row_info->width;
 443
 444             for (i = 0, sp = dp = row; i < row_width; i++)
 445             {
 446                png_byte save = *(sp++);
 447                *(dp++) = *(sp++);
 448                *(dp++) = save;
 449             }
 450          }
 451
 452 #ifdef PNG_WRITE_16BIT_SUPPORTED
 453          else
 454          {
 455             /* This converts from AAGG to GGAA */
 456             png_bytep sp, dp;
 457             png_uint_32 i;
 458             png_uint_32 row_width = row_info->width;
 459
 460             for (i = 0, sp = dp = row; i < row_width; i++)
 461             {
 462                png_byte save[2];
 463                save[0] = *(sp++);
 464                save[1] = *(sp++);
 465                *(dp++) = *(sp++);
 466                *(dp++) = *(sp++);
 467                *(dp++) = save[0];
 468                *(dp++) = save[1];
 469             }
 470          }
 471 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 472       }
 473    }
 474 }
 475 #endif
 476
 477 #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
 478 void /* PRIVATE */
 479 png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
 480 {
 481    png_debug(1, "in png_do_write_invert_alpha");
 482
 483    {
 484       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 485       {
 486          if (row_info->bit_depth == 8)
 487          {
 488             /* This inverts the alpha channel in RGBA */
 489             png_bytep sp, dp;
 490             png_uint_32 i;
 491             png_uint_32 row_width = row_info->width;
 492
 493             for (i = 0, sp = dp = row; i < row_width; i++)
 494             {
 495                /* Does nothing
 496                *(dp++) = *(sp++);
 497                *(dp++) = *(sp++);
 498                *(dp++) = *(sp++);
 499                */
 500                sp+=3; dp = sp;
 501                *(dp++) = (png_byte)(255 - *(sp++));
 502             }
 503          }
 504
 505 #ifdef PNG_WRITE_16BIT_SUPPORTED
 506          else
 507          {
 508             /* This inverts the alpha channel in RRGGBBAA */
 509             png_bytep sp, dp;
 510             png_uint_32 i;
 511             png_uint_32 row_width = row_info->width;
 512
 513             for (i = 0, sp = dp = row; i < row_width; i++)
 514             {
 515                /* Does nothing
 516                *(dp++) = *(sp++);
 517                *(dp++) = *(sp++);
 518                *(dp++) = *(sp++);
 519                *(dp++) = *(sp++);
 520                *(dp++) = *(sp++);
 521                *(dp++) = *(sp++);
 522                */
 523                sp+=6; dp = sp;
 524                *(dp++) = (png_byte)(255 - *(sp++));
 525                *(dp++) = (png_byte)(255 - *(sp++));
 526             }
 527          }
 528 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 529       }
 530
 531       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 532       {
 533          if (row_info->bit_depth == 8)
 534          {
 535             /* This inverts the alpha channel in GA */
 536             png_bytep sp, dp;
 537             png_uint_32 i;
 538             png_uint_32 row_width = row_info->width;
 539
 540             for (i = 0, sp = dp = row; i < row_width; i++)
 541             {
 542                *(dp++) = *(sp++);
 543                *(dp++) = (png_byte)(255 - *(sp++));
 544             }
 545          }
 546
 547 #ifdef PNG_WRITE_16BIT_SUPPORTED
 548          else
 549          {
 550             /* This inverts the alpha channel in GGAA */
 551             png_bytep sp, dp;
 552             png_uint_32 i;
 553             png_uint_32 row_width = row_info->width;
 554
 555             for (i = 0, sp = dp = row; i < row_width; i++)
 556             {
 557                /* Does nothing
 558                *(dp++) = *(sp++);
 559                *(dp++) = *(sp++);
 560                */
 561                sp+=2; dp = sp;
 562                *(dp++) = (png_byte)(255 - *(sp++));
 563                *(dp++) = (png_byte)(255 - *(sp++));
 564             }
 565          }
 566 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 567       }
 568    }
 569 }
 570 #endif
 571 #endif /* PNG_WRITE_TRANSFORMS_SUPPORTED */
 572
 573 #ifdef PNG_MNG_FEATURES_SUPPORTED
 574 /* Undoes intrapixel differencing  */
 575 void /* PRIVATE */
 576 png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
 577 {
 578    png_debug(1, "in png_do_write_intrapixel");
 579
 580    if ((row_info->color_type & PNG_COLOR_MASK_COLOR))
 581    {
 582       int bytes_per_pixel;
 583       png_uint_32 row_width = row_info->width;
 584       if (row_info->bit_depth == 8)
 585       {
 586          png_bytep rp;
 587          png_uint_32 i;
 588
 589          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 590             bytes_per_pixel = 3;
 591
 592          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 593             bytes_per_pixel = 4;
 594
 595          else
 596             return;
 597
 598          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
 599          {
 600             *(rp)     = (png_byte)((*rp       - *(rp + 1)) & 0xff);
 601             *(rp + 2) = (png_byte)((*(rp + 2) - *(rp + 1)) & 0xff);
 602          }
 603       }
 604
 605 #ifdef PNG_WRITE_16BIT_SUPPORTED
 606       else if (row_info->bit_depth == 16)
 607       {
 608          png_bytep rp;
 609          png_uint_32 i;
 610
 611          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
 612             bytes_per_pixel = 6;
 613
 614          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
 615             bytes_per_pixel = 8;
 616
 617          else
 618             return;
 619
 620          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
 621          {
 622             png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);
 623             png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);
 624             png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);
 625             png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);
 626             png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
 627             *(rp    ) = (png_byte)((red >> 8) & 0xff);
 628             *(rp + 1) = (png_byte)(red & 0xff);
 629             *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
 630             *(rp + 5) = (png_byte)(blue & 0xff);
 631          }
 632       }
 633 #endif /* PNG_WRITE_16BIT_SUPPORTED */
 634    }
 635 }
 636 #endif /* PNG_MNG_FEATURES_SUPPORTED */
 637 #endif /* PNG_WRITE_SUPPORTED */