2 /* pngwtran.c - transforms the data in a row for PNG writers
4 * Last changed in libpng 1.5.6 [November 3, 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.)
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
16 #ifdef PNG_WRITE_SUPPORTED
18 #ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
19 /* Transform the data according to the user's wishes. The order of
20 * transformations is significant.
23 png_do_write_transformations(png_structp png_ptr, png_row_infop row_info)
25 png_debug(1, "in png_do_write_transformations");
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
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 */
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));
52 #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
53 if (png_ptr->transformations & PNG_PACKSWAP)
54 png_do_packswap(row_info, png_ptr->row_buf + 1);
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);
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);
68 #ifdef PNG_WRITE_SHIFT_SUPPORTED
69 if (png_ptr->transformations & PNG_SHIFT)
70 png_do_shift(row_info, png_ptr->row_buf + 1,
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);
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);
84 #ifdef PNG_WRITE_BGR_SUPPORTED
85 if (png_ptr->transformations & PNG_BGR)
86 png_do_bgr(row_info, png_ptr->row_buf + 1);
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);
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).
101 png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
103 png_debug(1, "in png_do_pack");
105 if (row_info->bit_depth == 8 &&
106 row_info->channels == 1)
108 switch ((int)bit_depth)
115 png_uint_32 row_width = row_info->width;
122 for (i = 0; i < row_width; i++)
152 png_uint_32 row_width = row_info->width;
159 for (i = 0; i < row_width; i++)
163 value = (png_byte)(*sp & 0x03);
164 v |= (value << shift);
191 png_uint_32 row_width = row_info->width;
198 for (i = 0; i < row_width; i++)
202 value = (png_byte)(*sp & 0x0f);
203 v |= (value << shift);
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,
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
246 png_do_shift(png_row_infop row_info, png_bytep row,
247 png_const_color_8p bit_depth)
249 png_debug(1, "in png_do_shift");
251 if (row_info->color_type != PNG_COLOR_TYPE_PALETTE)
253 int shift_start[4], shift_dec[4];
256 if (row_info->color_type & PNG_COLOR_MASK_COLOR)
258 shift_start[channels] = row_info->bit_depth - bit_depth->red;
259 shift_dec[channels] = bit_depth->red;
262 shift_start[channels] = row_info->bit_depth - bit_depth->green;
263 shift_dec[channels] = bit_depth->green;
266 shift_start[channels] = row_info->bit_depth - bit_depth->blue;
267 shift_dec[channels] = bit_depth->blue;
273 shift_start[channels] = row_info->bit_depth - bit_depth->gray;
274 shift_dec[channels] = bit_depth->gray;
278 if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
280 shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
281 shift_dec[channels] = bit_depth->alpha;
285 /* With low row depths, could only be grayscale, so one channel */
286 if (row_info->bit_depth < 8)
291 png_size_t row_bytes = row_info->rowbytes;
293 if (bit_depth->gray == 1 && row_info->bit_depth == 2)
296 else if (row_info->bit_depth == 4 && bit_depth->gray == 3)
302 for (i = 0; i < row_bytes; i++, bp++)
310 for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
313 *bp |= (png_byte)((v << j) & 0xff);
316 *bp |= (png_byte)((v >> (-j)) & mask);
321 else if (row_info->bit_depth == 8)
325 png_uint_32 istop = channels * row_info->width;
327 for (i = 0; i < istop; i++, bp++)
332 int c = (int)(i%channels);
337 for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
340 *bp |= (png_byte)((v << j) & 0xff);
343 *bp |= (png_byte)((v >> (-j)) & 0xff);
352 png_uint_32 istop = channels * row_info->width;
354 for (bp = row, i = 0; i < istop; i++)
356 int c = (int)(i%channels);
357 png_uint_16 value, v;
360 v = (png_uint_16)(((png_uint_16)(*bp) << 8) + *(bp + 1));
363 for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
366 value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
369 value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
371 *bp++ = (png_byte)(value >> 8);
372 *bp++ = (png_byte)(value & 0xff);
379 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
381 png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
383 png_debug(1, "in png_do_write_swap_alpha");
386 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
388 if (row_info->bit_depth == 8)
390 /* This converts from ARGB to RGBA */
393 png_uint_32 row_width = row_info->width;
395 for (i = 0, sp = dp = row; i < row_width; i++)
397 png_byte save = *(sp++);
405 #ifdef PNG_WRITE_16BIT_SUPPORTED
408 /* This converts from AARRGGBB to RRGGBBAA */
411 png_uint_32 row_width = row_info->width;
413 for (i = 0, sp = dp = row; i < row_width; i++)
428 #endif /* PNG_WRITE_16BIT_SUPPORTED */
431 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
433 if (row_info->bit_depth == 8)
435 /* This converts from AG to GA */
438 png_uint_32 row_width = row_info->width;
440 for (i = 0, sp = dp = row; i < row_width; i++)
442 png_byte save = *(sp++);
448 #ifdef PNG_WRITE_16BIT_SUPPORTED
451 /* This converts from AAGG to GGAA */
454 png_uint_32 row_width = row_info->width;
456 for (i = 0, sp = dp = row; i < row_width; i++)
467 #endif /* PNG_WRITE_16BIT_SUPPORTED */
473 #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
475 png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
477 png_debug(1, "in png_do_write_invert_alpha");
480 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
482 if (row_info->bit_depth == 8)
484 /* This inverts the alpha channel in RGBA */
487 png_uint_32 row_width = row_info->width;
489 for (i = 0, sp = dp = row; i < row_width; i++)
497 *(dp++) = (png_byte)(255 - *(sp++));
501 #ifdef PNG_WRITE_16BIT_SUPPORTED
504 /* This inverts the alpha channel in RRGGBBAA */
507 png_uint_32 row_width = row_info->width;
509 for (i = 0, sp = dp = row; i < row_width; i++)
520 *(dp++) = (png_byte)(255 - *(sp++));
521 *(dp++) = (png_byte)(255 - *(sp++));
524 #endif /* PNG_WRITE_16BIT_SUPPORTED */
527 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
529 if (row_info->bit_depth == 8)
531 /* This inverts the alpha channel in GA */
534 png_uint_32 row_width = row_info->width;
536 for (i = 0, sp = dp = row; i < row_width; i++)
539 *(dp++) = (png_byte)(255 - *(sp++));
543 #ifdef PNG_WRITE_16BIT_SUPPORTED
546 /* This inverts the alpha channel in GGAA */
549 png_uint_32 row_width = row_info->width;
551 for (i = 0, sp = dp = row; i < row_width; i++)
558 *(dp++) = (png_byte)(255 - *(sp++));
559 *(dp++) = (png_byte)(255 - *(sp++));
562 #endif /* PNG_WRITE_16BIT_SUPPORTED */
567 #endif /* PNG_WRITE_TRANSFORMS_SUPPORTED */
569 #ifdef PNG_MNG_FEATURES_SUPPORTED
570 /* Undoes intrapixel differencing */
572 png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
574 png_debug(1, "in png_do_write_intrapixel");
576 if ((row_info->color_type & PNG_COLOR_MASK_COLOR))
579 png_uint_32 row_width = row_info->width;
580 if (row_info->bit_depth == 8)
585 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
588 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
594 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
596 *(rp) = (png_byte)((*rp - *(rp + 1)) & 0xff);
597 *(rp + 2) = (png_byte)((*(rp + 2) - *(rp + 1)) & 0xff);
601 #ifdef PNG_WRITE_16BIT_SUPPORTED
602 else if (row_info->bit_depth == 16)
607 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
610 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
616 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
618 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1);
619 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
620 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
621 png_uint_32 red = (png_uint_32)((s0 - s1) & 0xffffL);
622 png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
623 *(rp ) = (png_byte)((red >> 8) & 0xff);
624 *(rp + 1) = (png_byte)(red & 0xff);
625 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
626 *(rp + 5) = (png_byte)(blue & 0xff);
629 #endif /* PNG_WRITE_16BIT_SUPPORTED */
632 #endif /* PNG_MNG_FEATURES_SUPPORTED */
633 #endif /* PNG_WRITE_SUPPORTED */