This change:

- supports kGray correctly
- avoid extra call to png_get_IHDR by storing the bit depth
- call transforms as needed
- checks for tRNS alpha value in RGB and GRAY color types

BUG=skia:

Review URL: https://codereview.chromium.org/1214203005

1 files changed, 5 insertions, 2 deletions

diff --git a/src/codec/SkCodec_libpng.h b/src/codec/SkCodec_libpng.h
index a105c3c5e3..c0fee74e96 100644
--- a/src/codec/SkCodec_libpng.h
+++ b/src/codec/SkCodec_libpng.h
@@ -44,14 +44,17 @@ private:
     SkSwizzler::SrcConfig       fSrcConfig;
     int                         fNumberPasses;
     bool                        fReallyHasAlpha;
+    int                         fBitDepth;
 
-    SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop);
+    SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop, int);
     ~SkPngCodec();
 
+
     // Helper to set up swizzler and color table. Also calls png_read_update_info.
     Result initializeSwizzler(const SkImageInfo& requestedInfo, void* dst,
                               size_t rowBytes, const Options&, SkPMColor*, int* ctableCount);
-    // Calls rewindIfNeeded, and returns true if the decoder can continue.
+
+    // Calls rewindIfNeeded and returns true if the decoder can continue.
     bool handleRewind();
     bool decodePalette(bool premultiply, int bitDepth, int* ctableCount);
     void finish();