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src/driver/pictureviewer/png.cpp: Add support for gray scale PNGs...

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...with alpha channel
This commit is contained in:
M. Liebmann
2017-01-01 22:57:37 +01:00
parent b335408913
commit 79d9b88ae1
1 changed files with 40 additions and 6 deletions
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46
src/driver/pictureviewer/png.cpp
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@@ -35,6 +35,7 @@ int int_png_load(const char *name, unsigned char **buffer, int* xp, int* yp, int
int bit_depth, color_type, interlace_type, number_passes, pass, int_bpp; int bit_depth, color_type, interlace_type, number_passes, pass, int_bpp;
png_byte * fbptr; png_byte * fbptr;
FILE * fh; FILE * fh;
bool updateInfo_alreadyRead = false;
if(!(fh=fopen(name,"rb"))) if(!(fh=fopen(name,"rb")))
return(FH_ERROR_FILE); return(FH_ERROR_FILE);
@@ -63,18 +64,49 @@ int int_png_load(const char *name, unsigned char **buffer, int* xp, int* yp, int
png_init_io(png_ptr,fh); png_init_io(png_ptr,fh);
png_read_info(png_ptr, info_ptr); png_read_info(png_ptr, info_ptr);
png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, NULL, NULL); png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, NULL, NULL);
if (alpha) if (alpha) // 24bit or gray scale PNGs with alpha-channel
{ {
*bpp = png_get_channels(png_ptr, info_ptr); *bpp = png_get_channels(png_ptr, info_ptr);
if ((*bpp != 4) || !(color_type & PNG_COLOR_MASK_ALPHA)) if ((*bpp == 2) && (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)) {
{ if (bit_depth < 8) {
/* Extract multiple pixels with bit depths of 1, 2, and 4
from a single byte into separate bytes
(useful for paletted and grayscale images). */
png_set_packing(png_ptr);
/* Expand grayscale images to the full 8 bits
from 1, 2, or 4 bits/pixel */
#if PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR <= 2 && PNG_LIBPNG_VER_RELEASE < 9
png_set_gray_1_2_4_to_8(png_ptr);
#else
png_set_expand_gray_1_2_4_to_8(png_ptr);
#endif
}
/* Expand the grayscale to 24-bit RGB if necessary. */
png_set_gray_to_rgb(png_ptr);
/* Update the users info structure */
png_read_update_info(png_ptr, info_ptr);
updateInfo_alreadyRead = true;
*bpp = png_get_channels(png_ptr, info_ptr);
if (*bpp != 4) {
/* No 4 channels found
load PNG without alpha channel */
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
fclose(fh);
return fh_png_load(name, buffer, xp, yp);
}
}
else if ((*bpp != 4) || !(color_type & PNG_COLOR_MASK_ALPHA)) {
/* No 4 channels & not an alpha channel found
load PNG without alpha channel */
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
fclose(fh); fclose(fh);
return fh_png_load(name, buffer, xp, yp); return fh_png_load(name, buffer, xp, yp);
} }
// 24bit PNGs with alpha-channel
int_bpp = 4; int_bpp = 4;
// png_set_swap_alpha(png_ptr);
/* Expand paletted or RGB images with transparency
to full alpha channels so the data will
be available as RGBA quartets. */
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
png_set_tRNS_to_alpha(png_ptr); png_set_tRNS_to_alpha(png_ptr);
}else // All other PNGs }else // All other PNGs
@@ -105,7 +137,9 @@ int int_png_load(const char *name, unsigned char **buffer, int* xp, int* yp, int
if (bit_depth == 16) if (bit_depth == 16)
png_set_strip_16(png_ptr); png_set_strip_16(png_ptr);
number_passes = png_set_interlace_handling(png_ptr); number_passes = png_set_interlace_handling(png_ptr);
png_read_update_info(png_ptr,info_ptr); /* Update the users info structure */
if (!updateInfo_alreadyRead)
png_read_update_info(png_ptr,info_ptr);
unsigned long rowbytes = png_get_rowbytes(png_ptr, info_ptr); unsigned long rowbytes = png_get_rowbytes(png_ptr, info_ptr);
if (width * int_bpp != rowbytes) if (width * int_bpp != rowbytes)
{ {