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[devel] Clean up ALPHA flags and transformations
This commit is contained in:
John Bowler
committed by
Glenn Randers-Pehrson
Glenn Randers-Pehrson
parent
5432c01ffd
commit
9b872f4cf9
243
pngtrans.c
243
pngtrans.c
@@ -424,170 +424,115 @@ png_do_packswap(png_row_infop row_info, png_bytep row)
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#if defined(PNG_WRITE_FILLER_SUPPORTED) || \
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defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
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/* Remove filler or alpha byte(s) */
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/* Remove a channel - this used to be 'png_do_strip_filler' but it used a
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* somewhat weird combination of flags to determine what to do. All the calls
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* to png_do_strip_filler are changed in 1.5.2 to call this instead with the
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* correct arguments.
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*
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* The routine isn't general - the channel must be the channel at the start or
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* end (not in the middle) of each pixel.
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*/
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void /* PRIVATE */
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png_do_strip_filler(png_row_infop row_info, png_bytep row, png_uint_32 flags)
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png_do_strip_channel(png_row_infop row_info, png_bytep row, int at_start)
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{
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png_debug(1, "in png_do_strip_filler");
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png_bytep sp = row; /* source pointer */
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png_bytep dp = row; /* destination pointer */
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png_bytep ep = row + row_info->rowbytes; /* One beyond end of row */
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/* At the start sp will point to the first byte to copy and dp to where
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* it is copied to. ep always points just beyond the end of the row, so
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* the loop simply copies (channels-1) channels until sp reaches ep.
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*/
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/* GA, GX, XG cases */
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if (row_info->channels == 2)
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{
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png_bytep sp = row;
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png_bytep dp = row;
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png_uint_32 row_width = row_info->width;
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png_uint_32 i;
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if ((row_info->color_type == PNG_COLOR_TYPE_RGB ||
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(row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
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(flags & PNG_FLAG_STRIP_ALPHA))) &&
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row_info->channels == 4)
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if (row_info->bit_depth == 8)
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{
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if (row_info->bit_depth == 8)
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{
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/* This converts from RGBX or RGBA to RGB */
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if (flags & PNG_FLAG_FILLER_AFTER)
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{
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dp += 3; sp += 4;
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for (i = 1; i < row_width; i++)
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{
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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sp++;
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}
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}
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if (at_start) /* Skip initial filler */
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++sp;
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else /* Skip initial channels and, for sp, the filler */
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sp += 2, ++dp;
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/* This converts from XRGB or ARGB to RGB */
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else
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{
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for (i = 0; i < row_width; i++)
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{
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sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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}
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}
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row_info->pixel_depth = 24;
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row_info->rowbytes = row_width * 3;
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}
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/* For a 1 pixel wide image there is nothing to do */
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while (sp < ep)
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*dp++ = *sp, sp += 2;
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else /* if (row_info->bit_depth == 16) */
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{
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if (flags & PNG_FLAG_FILLER_AFTER)
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{
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/* This converts from RRGGBBXX or RRGGBBAA to RRGGBB */
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sp += 8; dp += 6;
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for (i = 1; i < row_width; i++)
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{
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/* This could be (although png_memcpy is probably slower):
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png_memcpy(dp, sp, 6);
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sp += 8;
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dp += 6;
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*/
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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sp += 2;
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}
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}
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else
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{
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/* This converts from XXRRGGBB or AARRGGBB to RRGGBB */
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for (i = 0; i < row_width; i++)
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{
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/* This could be (although png_memcpy is probably slower):
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png_memcpy(dp, sp, 6);
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sp += 8;
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dp += 6;
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*/
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sp += 2;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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}
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}
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row_info->pixel_depth = 48;
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row_info->rowbytes = row_width * 6;
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}
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row_info->channels = 3;
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row_info->pixel_depth = 8;
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}
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else if ((row_info->color_type == PNG_COLOR_TYPE_GRAY ||
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(row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
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(flags & PNG_FLAG_STRIP_ALPHA))) &&
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row_info->channels == 2)
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else if (row_info->bit_depth == 16)
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{
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if (row_info->bit_depth == 8)
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{
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if (flags & PNG_FLAG_FILLER_AFTER)
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{
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/* This converts from GX or GA to G */
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for (i = 0; i < row_width; i++)
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{
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*dp++ = *sp++;
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sp++;
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}
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}
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if (at_start)
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sp += 2;
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else
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sp += 4, dp += 2;
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else
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{
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/* This converts from XG or AG to G */
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for (i = 0; i < row_width; i++)
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{
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sp++;
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*dp++ = *sp++;
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}
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}
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while (sp < ep)
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*dp++ = *sp++, *dp++ = *sp, sp += 3;
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row_info->pixel_depth = 8;
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row_info->rowbytes = row_width;
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}
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else /* if (row_info->bit_depth == 16) */
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{
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if (flags & PNG_FLAG_FILLER_AFTER)
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{
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/* This converts from GGXX or GGAA to GG */
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sp += 4; dp += 2;
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for (i = 1; i < row_width; i++)
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{
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*dp++ = *sp++;
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*dp++ = *sp++;
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sp += 2;
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}
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}
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else
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{
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/* This converts from XXGG or AAGG to GG */
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for (i = 0; i < row_width; i++)
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{
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sp += 2;
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*dp++ = *sp++;
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*dp++ = *sp++;
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}
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}
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row_info->pixel_depth = 16;
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row_info->rowbytes = row_width * 2;
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}
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row_info->channels = 1;
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row_info->pixel_depth = 16;
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}
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if (flags & PNG_FLAG_STRIP_ALPHA)
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row_info->color_type = (png_byte)(row_info->color_type &
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~PNG_COLOR_MASK_ALPHA);
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else
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return; /* bad bit depth */
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row_info->channels = 1;
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/* Finally fix the color type if it records an alpha channel */
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if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
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row_info->color_type = PNG_COLOR_TYPE_GRAY;
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}
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/* RGBA, RGBX, XRGB cases */
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else if (row_info->channels == 4)
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{
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if (row_info->bit_depth == 8)
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{
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if (at_start) /* Skip initial filler */
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++sp;
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else /* Skip initial channels and, for sp, the filler */
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sp += 4, dp += 3;
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/* Note that the loop adds 3 to dp and 4 to sp each time. */
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while (sp < ep)
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*dp++ = *sp++, *dp++ = *sp++, *dp++ = *sp, sp += 2;
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row_info->pixel_depth = 24;
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}
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else if (row_info->bit_depth == 16)
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{
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if (at_start)
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sp += 2;
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else
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sp += 8, dp += 6;
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while (sp < ep)
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{
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/* Copy 6 bytes, skip 2 */
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*dp++ = *sp++, *dp++ = *sp++;
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*dp++ = *sp++, *dp++ = *sp++;
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*dp++ = *sp++, *dp++ = *sp, sp += 3;
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}
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row_info->pixel_depth = 48;
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}
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else
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return; /* bad bit depth */
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row_info->channels = 3;
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/* Finally fix the color type if it records an alpha channel */
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if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
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row_info->color_type = PNG_COLOR_TYPE_RGB;
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}
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else
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return; /* The filler channel has gone already */
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/* Fix the rowbytes value. */
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row_info->rowbytes = dp-row;
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}
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#endif
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