Early reporting of opaqueness by decoders.

third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  * Portions are Copyright (C) 2001 mozilla.org
  *
  * Other contributors:
  *   Stuart Parmenter <stuart@mozilla.com>
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 74 matching lines @@
 
 class PNGImageReader final {
     USING_FAST_MALLOC(PNGImageReader);
     WTF_MAKE_NONCOPYABLE(PNGImageReader);
 public:
     PNGImageReader(PNGImageDecoder* decoder, size_t readOffset)
         : m_decoder(decoder)
         , m_readOffset(readOffset)
         , m_currentBufferSize(0)
         , m_decodingSizeOnly(false)
-        , m_hasAlpha(false)
+        , m_hasAlpha(true)
 #if USE(QCMSLIB)
         , m_rowBuffer()
 #endif
     {
         m_png = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, pngFailed, 0);
         m_info = png_create_info_struct(m_png);
         png_set_progressive_read_fn(m_png, m_decoder, pngHeaderAvailable, pngRowAvailable, pngComplete);
     }
 
     ~PNGImageReader()
@@ skipping 57 matching lines @@
 PNGImageDecoder::PNGImageDecoder(AlphaOption alphaOption, GammaAndColorProfileOption colorOptions, size_t maxDecodedBytes, size_t offset)
     : ImageDecoder(alphaOption, colorOptions, maxDecodedBytes)
     , m_offset(offset)
 {
 }
 
 PNGImageDecoder::~PNGImageDecoder()
 {
 }
 
+bool PNGImageDecoder::frameHasAlphaAtIndex(size_t index) const
+{
+    if (index == 0 && isAllDataReceived() && m_reader && !m_reader->hasAlpha())
+        return false;
+    return ImageDecoder::frameHasAlphaAtIndex(index);
+}
+
 void PNGImageDecoder::headerAvailable()
 {
     png_structp png = m_reader->pngPtr();
     png_infop info = m_reader->infoPtr();
     png_uint_32 width = png_get_image_width(png, info);
     png_uint_32 height = png_get_image_height(png, info);
 
     // Protect against large PNGs. See http://bugzil.la/251381 for more details.
     const unsigned long maxPNGSize = 1000000UL;
     if (width > maxPNGSize || height > maxPNGSize) {
@@ skipping 249 matching lines @@
     // has failed.
     if (!m_reader->decode(*m_data, onlySize) && isAllDataReceived())
         setFailed();
 
     // If decoding is done or failed, we don't need the PNGImageReader anymore.
     if (isComplete(this) || failed())
         m_reader.clear();
 }
 
 } // namespace blink