[HTMLCanvasElement.toBlob] Default callback version without scheduler

Source/platform/graphics/ImageBuffer.cpp

 /*
  * Copyright (c) 2008, Google Inc. All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
@@ skipping 323 matching lines @@
     ASSERT(originY >= 0);
     ASSERT(originY < sourceRect.maxY());
 
     const size_t srcBytesPerRow = 4 * sourceSize.width();
     const void* srcAddr = source + originY * srcBytesPerRow + originX * 4;
     SkAlphaType alphaType = (multiplied == Premultiplied) ? kPremul_SkAlphaType : kUnpremul_SkAlphaType;
     SkImageInfo info = SkImageInfo::Make(sourceRect.width(), sourceRect.height(), kRGBA_8888_SkColorType, alphaType);
     m_surface->writePixels(info, srcAddr, srcBytesPerRow, destX, destY);
 }
 
-static bool encodeImage(const ImageDataBuffer& source, const String& mimeType, const double* quality, Vector<char>* output)
+bool ImageDataBuffer::encodeImage(const String& mimeType, const double* quality, Vector<char>* output) const

[Noel Gordon, 2015/08/28 08:53:47]

This function was moved to ImageDataBuffer so toBlob can call it directly, but
the ASSERT that

  ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));

seems to be gone. The toDataURL code path has that ASSERT, but the toBlob code
path does not (unless I missed it).  How come?

[xlai (Olivia), 2015/08/28 19:54:19]

I believe that this ASSERT in toDataURL is redundant. I can take away that in
future commit.

Both toDataURL and toBlob call an internal method in HTMLCanvasElement.cpp
called "HTMLCanvasElement::toEncodingMimeType(const String& mimeType)" and that
method already invokes "MIMETypeRegistry::isSupportedImageMIMETypeForEncoding".
So by the time when the execution reaches encodeImage, it is already guaranteed
that the mime type is a supported type. One of my layout test does prove
unsupported mime type does fall back to default png.

 {
     Vector<unsigned char>* encodedImage = reinterpret_cast<Vector<unsigned char>*>(output);
 
     if (mimeType == "image/jpeg") {
         int compressionQuality = JPEGImageEncoder::DefaultCompressionQuality;
         if (quality && *quality >= 0.0 && *quality <= 1.0)
             compressionQuality = static_cast<int>(*quality * 100 + 0.5);
-        if (!JPEGImageEncoder::encode(source, compressionQuality, encodedImage))
+        if (!JPEGImageEncoder::encode(*this, compressionQuality, encodedImage))
             return false;
     } else if (mimeType == "image/webp") {
         int compressionQuality = WEBPImageEncoder::DefaultCompressionQuality;
         if (quality && *quality >= 0.0 && *quality <= 1.0)
             compressionQuality = static_cast<int>(*quality * 100 + 0.5);
-        if (!WEBPImageEncoder::encode(source, compressionQuality, encodedImage))
+        if (!WEBPImageEncoder::encode(*this, compressionQuality, encodedImage))
             return false;
     } else {
-        if (!PNGImageEncoder::encode(source, encodedImage))
+        if (!PNGImageEncoder::encode(*this, encodedImage))
             return false;
         ASSERT(mimeType == "image/png");
     }
 
     return true;
 }
 
 String ImageDataBuffer::toDataURL(const String& mimeType, const double* quality) const
 {
     ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
 
     Vector<char> encodedImage;
-    if (!encodeImage(*this, mimeType, quality, &encodedImage))
+    if (!encodeImage(mimeType, quality, &encodedImage))
         return "data:,";
 
     return "data:" + mimeType + ";base64," + base64Encode(encodedImage);
 }
 
 } // namespace blink