-/* From Andreas Dilger e-mail to png-implement, 26 March 1998:
- *
- * In most cases, the "simple transparency" should be done prior to doing
- * gray-to-RGB, or you will have to test 3x as many bytes to check if a
- * pixel is transparent. You would also need to make sure that the
- * transparency information is upgraded to RGB.
- *
- * To summarize, the current flow is:
- * - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
- * with background "in place" if transparent,
- * convert to RGB if necessary
- * - Gray + alpha -> composite with gray background and remove alpha bytes,
- * convert to RGB if necessary
- *
- * To support RGB backgrounds for gray images we need:
- * - Gray + simple transparency -> convert to RGB + simple transparency,
- * compare 3 or 6 bytes and composite with
- * background "in place" if transparent
- * (3x compare/pixel compared to doing
- * composite with gray bkgrnd)
- * - Gray + alpha -> convert to RGB + alpha, composite with background and
- * remove alpha bytes (3x float
- * operations/pixel compared with composite
- * on gray background)
- *
- * Greg's change will do this. The reason it wasn't done before is for
- * performance, as this increases the per-pixel operations. If we would check
- * in advance if the background was gray or RGB, and position the gray-to-RGB
- * transform appropriately, then it would save a lot of work/time.
- */
-
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
- /* If gray -> RGB, do so now only if background is non-gray; else do later
- * for performance reasons
- */
- if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
- !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
- png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
-#endif
-
-#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
- (defined PNG_READ_ALPHA_MODE_SUPPORTED)
- if (png_ptr->transformations & PNG_COMPOSE)
- png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
-#endif
-
-#ifdef PNG_READ_GAMMA_SUPPORTED
- if ((png_ptr->transformations & PNG_GAMMA) &&
-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
- /* Because RGB_TO_GRAY does the gamma transform. */
- !(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
-#endif
-#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
- (defined PNG_READ_ALPHA_MODE_SUPPORTED)
- /* Because PNG_COMPOSE does the gamma transform if there is something to
- * do (if there is an alpha channel or transparency.)
- */
- !((png_ptr->transformations & PNG_COMPOSE) &&
- ((png_ptr->num_trans != 0) ||
- (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
-#endif
- /* Because png_init_read_transformations transforms the palette, unless
- * RGB_TO_GRAY will do the transform.
- */
- (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
- png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
-#endif
-
-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
- if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
- (png_ptr->transformations & PNG_COMPOSE) &&
- (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
- row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
- png_do_strip_channel(row_info, png_ptr->row_buf + 1,
- 0 /* at_start == false, because SWAP_ALPHA happens later */);
-#endif
-
-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
- if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
- (row_info->color_type & PNG_COLOR_MASK_ALPHA))
- png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
-#endif
-
-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
- if (png_ptr->transformations & PNG_SCALE_16_TO_8)
- png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
- /* There is no harm in doing both of these because only one has any effect,
- * by putting the 'scale' option first if the app asks for scale (either by
- * calling the API or in a TRANSFORM flag) this is what happens.
- */
- if (png_ptr->transformations & PNG_16_TO_8)
- png_do_chop(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_QUANTIZE_SUPPORTED
- if (png_ptr->transformations & PNG_QUANTIZE)
- {
- png_do_quantize(row_info, png_ptr->row_buf + 1,
- png_ptr->palette_lookup, png_ptr->quantize_index);
-
- if (row_info->rowbytes == 0)
- png_error(png_ptr, "png_do_quantize returned rowbytes=0");
- }
-#endif /* PNG_READ_QUANTIZE_SUPPORTED */
-
-#ifdef PNG_READ_EXPAND_16_SUPPORTED
- /* Do the expansion now, after all the arithmetic has been done. Notice
- * that previous transformations can handle the PNG_EXPAND_16 flag if this
- * is efficient (particularly true in the case of gamma correction, where
- * better accuracy results faster!)
- */
- if (png_ptr->transformations & PNG_EXPAND_16)
- png_do_expand_16(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
- /*NOTE: moved here in 1.5.4 (from much later in this list.) */
- if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
- (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
- png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_INVERT_SUPPORTED
- if (png_ptr->transformations & PNG_INVERT_MONO)
- png_do_invert(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_SHIFT_SUPPORTED
- if (png_ptr->transformations & PNG_SHIFT)
- png_do_unshift(row_info, png_ptr->row_buf + 1,
- &(png_ptr->shift));
-#endif
-
-#ifdef PNG_READ_PACK_SUPPORTED
- if (png_ptr->transformations & PNG_PACK)
- png_do_unpack(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_BGR_SUPPORTED
- if (png_ptr->transformations & PNG_BGR)
- png_do_bgr(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
- if (png_ptr->transformations & PNG_PACKSWAP)
- png_do_packswap(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_FILLER_SUPPORTED
- if (png_ptr->transformations & PNG_FILLER)
- png_do_read_filler(row_info, png_ptr->row_buf + 1,
- (png_uint_32)png_ptr->filler, png_ptr->flags);
-#endif
-
-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
- if (png_ptr->transformations & PNG_INVERT_ALPHA)
- png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
- if (png_ptr->transformations & PNG_SWAP_ALPHA)
- png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_16BIT_SUPPORTED
-#ifdef PNG_READ_SWAP_SUPPORTED
- if (png_ptr->transformations & PNG_SWAP_BYTES)
- png_do_swap(row_info, png_ptr->row_buf + 1);
-#endif
-#endif
-
-#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
- if (png_ptr->transformations & PNG_USER_TRANSFORM)
- {
- if (png_ptr->read_user_transform_fn != NULL)
- (*(png_ptr->read_user_transform_fn)) /* User read transform function */
- (png_ptr, /* png_ptr */
- row_info, /* row_info: */
- /* png_uint_32 width; width of row */
- /* png_size_t rowbytes; number of bytes in row */
- /* png_byte color_type; color type of pixels */
- /* png_byte bit_depth; bit depth of samples */
- /* png_byte channels; number of channels (1-4) */
- /* png_byte pixel_depth; bits per pixel (depth*channels) */
- png_ptr->row_buf + 1); /* start of pixel data for row */
-#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
- if (png_ptr->user_transform_depth)
- row_info->bit_depth = png_ptr->user_transform_depth;
-
- if (png_ptr->user_transform_channels)
- row_info->channels = png_ptr->user_transform_channels;
-#endif
- row_info->pixel_depth = (png_byte)(row_info->bit_depth *
- row_info->channels);
-
- row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
- }
-#endif
-}
-
-#ifdef PNG_READ_PACK_SUPPORTED
-/* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
- * without changing the actual values. Thus, if you had a row with
- * a bit depth of 1, you would end up with bytes that only contained
- * the numbers 0 or 1. If you would rather they contain 0 and 255, use
- * png_do_shift() after this.
- */
-void /* PRIVATE */
-png_do_unpack(png_row_infop row_info, png_bytep row)
-{
- png_debug(1, "in png_do_unpack");
-
- if (row_info->bit_depth < 8)
- {
- png_uint_32 i;
- png_uint_32 row_width=row_info->width;
-
- switch (row_info->bit_depth)
- {
- case 1:
- {
- png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
- png_bytep dp = row + (png_size_t)row_width - 1;
- png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
- for (i = 0; i < row_width; i++)
- {
- *dp = (png_byte)((*sp >> shift) & 0x01);
-
- if (shift == 7)
- {
- shift = 0;
- sp--;
- }
-
- else
- shift++;
-
- dp--;
- }
- break;
- }
-
- case 2:
- {
-
- png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
- png_bytep dp = row + (png_size_t)row_width - 1;
- png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
- for (i = 0; i < row_width; i++)
- {
- *dp = (png_byte)((*sp >> shift) & 0x03);
-
- if (shift == 6)
- {
- shift = 0;
- sp--;
- }
-
- else
- shift += 2;
-
- dp--;
- }
- break;
- }
-
- case 4:
- {
- png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
- png_bytep dp = row + (png_size_t)row_width - 1;
- png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
- for (i = 0; i < row_width; i++)
- {
- *dp = (png_byte)((*sp >> shift) & 0x0f);
-
- if (shift == 4)
- {
- shift = 0;
- sp--;
- }
-
- else
- shift = 4;
-
- dp--;
- }
- break;
- }
-
- default:
- break;
- }
- row_info->bit_depth = 8;
- row_info->pixel_depth = (png_byte)(8 * row_info->channels);
- row_info->rowbytes = row_width * row_info->channels;
- }
-}
-#endif
-
-#ifdef PNG_READ_SHIFT_SUPPORTED
-/* Reverse the effects of png_do_shift. This routine merely shifts the
- * pixels back to their significant bits values. Thus, if you have
- * a row of bit depth 8, but only 5 are significant, this will shift
- * the values back to 0 through 31.
- */
-void /* PRIVATE */
-png_do_unshift(png_row_infop row_info, png_bytep row,
- png_const_color_8p sig_bits)
-{
- int color_type;
-
- png_debug(1, "in png_do_unshift");
-
- /* The palette case has already been handled in the _init routine. */
- color_type = row_info->color_type;
-
- if (color_type != PNG_COLOR_TYPE_PALETTE)
- {
- int shift[4];
- int channels = 0;
- int bit_depth = row_info->bit_depth;
-
- if (color_type & PNG_COLOR_MASK_COLOR)
- {
- shift[channels++] = bit_depth - sig_bits->red;
- shift[channels++] = bit_depth - sig_bits->green;
- shift[channels++] = bit_depth - sig_bits->blue;
- }
-
- else
- {
- shift[channels++] = bit_depth - sig_bits->gray;
- }
-
- if (color_type & PNG_COLOR_MASK_ALPHA)