only upscale to 565 from palette if the colortable is opaque
diff --git a/src/images/SkImageDecoder_libpng.cpp b/src/images/SkImageDecoder_libpng.cpp
index e9e948b..6df56b4 100644
--- a/src/images/SkImageDecoder_libpng.cpp
+++ b/src/images/SkImageDecoder_libpng.cpp
@@ -110,10 +110,30 @@
return reallyHasAlpha;
}
-static inline bool isDirectModel(SkBitmap::Config config) {
- return config == SkBitmap::kARGB_8888_Config ||
- config == SkBitmap::kARGB_4444_Config ||
- config == SkBitmap::kRGB_565_Config;
+static bool canUpscalePaletteToConfig(SkBitmap::Config prefConfig,
+ bool srcHasAlpha) {
+ switch (prefConfig) {
+ case SkBitmap::kARGB_8888_Config:
+ case SkBitmap::kARGB_4444_Config:
+ return true;
+ case SkBitmap::kRGB_565_Config:
+ // only return true if the src is opaque (since 565 is opaque)
+ return !srcHasAlpha;
+ default:
+ return false;
+ }
+}
+
+// call only if color_type is PALETTE. Returns true if the ctable has alpha
+static bool hasTransparencyInPalette(png_structp png_ptr, png_infop info_ptr) {
+ png_bytep trans;
+ int num_trans;
+
+ if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
+ png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, NULL);
+ return num_trans > 0;
+ }
+ return false;
}
bool SkPNGImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* decodedBitmap,
@@ -214,9 +234,9 @@
if (color_type == PNG_COLOR_TYPE_PALETTE) {
config = SkBitmap::kIndex8_Config;
- if (isDirectModel(prefConfig)) {
- // todo: as we do below, if the palette has alpha, we should could
- // decide to not allow conversion to 565...
+ // now see if we can upscale to their requested config
+ bool paletteHasAlpha = hasTransparencyInPalette(png_ptr, info_ptr);
+ if (canUpscalePaletteToConfig(prefConfig, paletteHasAlpha)) {
config = prefConfig;
}
} else {
