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Use libpng's full API so we can ignore gamma. Fixes Driver '76's icon. #20033

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merged 1 commit into from
Feb 25, 2025
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Use libpng's full API so we can ignore gamma. Fixes Driver '76's icon. #20033

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77 changes: 61 additions & 16 deletions Common/Data/Format/PNGLoad.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,32 +31,77 @@ int pngLoad(const char *file, int *pwidth, int *pheight, unsigned char **image_d
return 1;
}

// Custom error handler
void pngErrorHandler(png_structp png_ptr, png_const_charp error_msg) {
ERROR_LOG(Log::System, "libpng error: %s\n", error_msg);
longjmp(png_jmpbuf(png_ptr), 1);
}

int pngLoadPtr(const unsigned char *input_ptr, size_t input_len, int *pwidth, int *pheight, unsigned char **image_data_ptr) {
png_image png{};
png.version = PNG_IMAGE_VERSION;
png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, pngErrorHandler, NULL);
if (!png) {
return 0;
}

png_image_begin_read_from_memory(&png, input_ptr, input_len);
// Ignore incorrect sRGB profiles
png_set_option(png, PNG_SKIP_sRGB_CHECK_PROFILE, PNG_OPTION_ON);

if (PNG_IMAGE_FAILED(png)) {
WARN_LOG(Log::IO, "pngLoad: %s", png.message);
*image_data_ptr = nullptr;
png_infop info = png_create_info_struct(png);
if (!info) {
png_destroy_read_struct(&png, NULL, NULL);
return 0;
}
*pwidth = png.width;
*pheight = png.height;
png.format = PNG_FORMAT_RGBA;

int stride = PNG_IMAGE_ROW_STRIDE(png);

size_t size = PNG_IMAGE_SIZE(png);
if (!size) {
ERROR_LOG(Log::IO, "pngLoad: empty image");
*image_data_ptr = nullptr;
if (setjmp(png_jmpbuf(png))) {
png_destroy_read_struct(&png, &info, NULL);
return 0;
}

png_set_read_fn(png, (png_voidp)&input_ptr, [](png_structp png_ptr, png_bytep outBytes, png_size_t byteCountToRead) {
const unsigned char **input = (const unsigned char **)png_get_io_ptr(png_ptr);
memcpy(outBytes, *input, byteCountToRead);
*input += byteCountToRead;
});

png_read_info(png, info);

*pwidth = png_get_image_width(png, info);
*pheight = png_get_image_height(png, info);

png_set_strip_16(png);
png_set_packing(png);
png_set_palette_to_rgb(png);
png_set_tRNS_to_alpha(png);
// Expand grayscale to RGB
if (png_get_color_type(png, info) == PNG_COLOR_TYPE_GRAY || png_get_color_type(png, info) == PNG_COLOR_TYPE_GRAY_ALPHA) {
png_set_gray_to_rgb(png);
}
// Force 8-bit RGBA format
png_set_filler(png, 0xFF, PNG_FILLER_AFTER);

// Ignore the file's gamma correction
png_set_gamma(png, 1.0, 1.0);

png_read_update_info(png, info);

size_t row_bytes = png_get_rowbytes(png, info);
size_t size = row_bytes * (*pheight);

*image_data_ptr = (unsigned char *)malloc(size);
png_image_finish_read(&png, NULL, *image_data_ptr, stride, NULL);
if (!*image_data_ptr) {
png_destroy_read_struct(&png, &info, NULL);
return 0;
}

png_bytep *row_pointers = (png_bytep *)malloc(sizeof(png_bytep) * (*pheight));
for (int y = 0; y < *pheight; y++) {
row_pointers[y] = *image_data_ptr + y * row_bytes;
}

png_read_image(png, row_pointers);
free(row_pointers);
png_destroy_read_struct(&png, &info, NULL);

return 1;
}

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