Support lossy and lossless <canvas>.toDataURL for webp

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);
 }
 
-bool ImageDataBuffer::encodeImage(const String& mimeType, const double* quality, Vector<char>* output) const
+bool ImageDataBuffer::encodeImage(const String& mimeType, const double* quality, Vector<char>* output, String* outputMimeType) const
 {
+    ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
+
     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(*this, compressionQuality, encodedImage))
             return false;
+    } else if (mimeType == "image/webp.ll") {
+        int compressionQuality = WEBPImageEncoder::DefaultCompressionQuality;
+        if (quality && *quality >= 0.0 && *quality <= 1.0)
+            compressionQuality = static_cast<int>(*quality * 100 + 0.5);
+        if (!WEBPImageEncoder::encode(*this, compressionQuality, encodedImage, WEBPImageEncoder::Lossless))
+            return false;
+        // webp.ll is an encoder selector: map it to the encoded image mimeType "image/webp".
+        *outputMimeType = "image/webp";
+        return true;
     } 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(*this, compressionQuality, encodedImage))
             return false;
     } else {
         if (!PNGImageEncoder::encode(*this, encodedImage))
             return false;
         ASSERT(mimeType == "image/png");
     }
 
+    *outputMimeType = mimeType;
     return true;
 }
 
 String ImageDataBuffer::toDataURL(const String& mimeType, const double* quality) const
 {
-    ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
-
     Vector<char> encodedImage;
-    if (!encodeImage(mimeType, quality, &encodedImage))
+    String encodedMimeType;
+    if (!encodeImage(mimeType, quality, &encodedImage, &encodedMimeType))
         return "data:,";
 
-    return "data:" + mimeType + ";base64," + base64Encode(encodedImage);
+    return "data:" + encodedMimeType + ";base64," + base64Encode(encodedImage);
 }
 
 } // namespace blink