int ReadPNG(const uint8_t* const data, size_t data_size,
struct WebPPicture* const pic,
int keep_alpha, struct Metadata* const metadata) {
volatile png_structp png = NULL;
volatile png_infop info = NULL;
volatile png_infop end_info = NULL;
PNGReadContext context = { NULL, 0, 0 };
int color_type, bit_depth, interlaced;
int has_alpha;
int num_passes;
int p;
volatile int ok = 0;
png_uint_32 width, height, y;
int64_t stride;
uint8_t* volatile rgb = NULL;
if (data == NULL || data_size == 0 || pic == NULL) return 0;
context.data = data;
context.data_size = data_size;
png = png_create_read_struct_2(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL,
NULL, MallocFunc, FreeFunc);
if (png == NULL) goto End;
png_set_error_fn(png, 0, error_function, NULL);
if (setjmp(png_jmpbuf(png))) {
Error:
MetadataFree(metadata);
goto End;
}
info = png_create_info_struct(png);
if (info == NULL) goto Error;
end_info = png_create_info_struct(png);
if (end_info == NULL) goto Error;
png_set_read_fn(png, &context, ReadFunc);
png_read_info(png, info);
if (!png_get_IHDR(png, info,
&width, &height, &bit_depth, &color_type, &interlaced,
NULL, NULL)) goto Error;
png_set_strip_16(png);
png_set_packing(png);
if (color_type == PNG_COLOR_TYPE_PALETTE) {
png_set_palette_to_rgb(png);
}
if (color_type == PNG_COLOR_TYPE_GRAY ||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
if (bit_depth < 8) {
png_set_expand_gray_1_2_4_to_8(png);
}
png_set_gray_to_rgb(png);
}
if (png_get_valid(png, info, PNG_INFO_tRNS)) {
png_set_tRNS_to_alpha(png);
has_alpha = 1;
} else {
has_alpha = !!(color_type & PNG_COLOR_MASK_ALPHA);
}
// Apply gamma correction if needed.
{
double image_gamma = 1 / 2.2, screen_gamma = 2.2;
int srgb_intent;
if (png_get_sRGB(png, info, &srgb_intent) ||
png_get_gAMA(png, info, &image_gamma)) {
png_set_gamma(png, screen_gamma, image_gamma);
}
}
if (!keep_alpha) {
png_set_strip_alpha(png);
has_alpha = 0;
}
num_passes = png_set_interlace_handling(png);
png_read_update_info(png, info);
stride = (int64_t)(has_alpha ? 4 : 3) * width * sizeof(*rgb);
if (stride != (int)stride ||
!ImgIoUtilCheckSizeArgumentsOverflow(stride, height)) {
goto Error;
}
rgb = (uint8_t*)malloc((size_t)stride * height);
if (rgb == NULL) goto Error;
for (p = 0; p < num_passes; ++p) {
png_bytep row = rgb;
for (y = 0; y < height; ++y) {
png_read_rows(png, &row, NULL, 1);
row += stride;
}
}
png_read_end(png, end_info);
if (metadata != NULL &&
!ExtractMetadataFromPNG(png, info, end_info, metadata)) {
fprintf(stderr, "Error extracting PNG metadata!\n");
goto Error;
}
pic->width = (int)width;
pic->height = (int)height;
ok = has_alpha ? WebPPictureImportRGBA(pic, rgb, (int)stride)
: WebPPictureImportRGB(pic, rgb, (int)stride);
if (!ok) {
goto Error;
}
End:
if (png != NULL) {
png_destroy_read_struct((png_structpp)&png,
(png_infopp)&info, (png_infopp)&end_info);
}
free(rgb);
return ok;
}
int ReadPNG(FILE* in_file, WebPPicture* const pic, int keep_alpha,
Metadata* const metadata) {
png_structp png;
png_infop info = NULL;
png_infop end_info = NULL;
int color_type, bit_depth, interlaced;
int has_alpha;
int num_passes;
int p;
int ok = 0;
png_uint_32 width, height, y;
int stride;
uint8_t* rgb = NULL;
png = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
if (png == NULL) {
goto End;
}
png_set_error_fn(png, 0, error_function, NULL);
if (setjmp(png_jmpbuf(png))) {
Error:
MetadataFree(metadata);
png_destroy_read_struct(&png, &info, &end_info);
goto End;
}
info = png_create_info_struct(png);
if (info == NULL) goto Error;
end_info = png_create_info_struct(png);
if (end_info == NULL) goto Error;
png_init_io(png, in_file);
png_read_info(png, info);
if (!png_get_IHDR(png, info,
&width, &height, &bit_depth, &color_type, &interlaced,
NULL, NULL)) goto Error;
png_set_strip_16(png);
png_set_packing(png);
if (color_type == PNG_COLOR_TYPE_PALETTE) png_set_palette_to_rgb(png);
if (color_type == PNG_COLOR_TYPE_GRAY ||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
if (bit_depth < 8) {
png_set_expand_gray_1_2_4_to_8(png);
}
png_set_gray_to_rgb(png);
}
if (png_get_valid(png, info, PNG_INFO_tRNS)) {
png_set_tRNS_to_alpha(png);
has_alpha = 1;
} else {
has_alpha = !!(color_type & PNG_COLOR_MASK_ALPHA);
}
if (!keep_alpha) {
png_set_strip_alpha(png);
has_alpha = 0;
}
num_passes = png_set_interlace_handling(png);
png_read_update_info(png, info);
stride = (has_alpha ? 4 : 3) * width * sizeof(*rgb);
rgb = (uint8_t*)malloc(stride * height);
if (rgb == NULL) goto Error;
for (p = 0; p < num_passes; ++p) {
for (y = 0; y < height; ++y) {
png_bytep row = rgb + y * stride;
png_read_rows(png, &row, NULL, 1);
}
}
png_read_end(png, end_info);
if (metadata != NULL &&
!ExtractMetadataFromPNG(png, info, end_info, metadata)) {
fprintf(stderr, "Error extracting PNG metadata!\n");
goto Error;
}
png_destroy_read_struct(&png, &info, &end_info);
pic->width = width;
pic->height = height;
ok = has_alpha ? WebPPictureImportRGBA(pic, rgb, stride)
: WebPPictureImportRGB(pic, rgb, stride);
if (!ok) {
goto Error;
}
End:
free(rgb);
return ok;
}
