Support lossy and lossless <canvas>.toDataURL for webp

Source/platform/image-encoders/skia/WEBPImageEncoder.cpp

Index: Source/platform/image-encoders/skia/WEBPImageEncoder.cpp
diff --git a/Source/platform/image-encoders/skia/WEBPImageEncoder.cpp b/Source/platform/image-encoders/skia/WEBPImageEncoder.cpp
index 0193b5df713d162259ffcdf8dbbab14181379c45..a680d25bb6e33adec9f2d685efda3aff48b16ce9 100644
--- a/Source/platform/image-encoders/skia/WEBPImageEncoder.cpp
+++ b/Source/platform/image-encoders/skia/WEBPImageEncoder.cpp
@@ -35,43 +35,19 @@
 #include "platform/graphics/ImageBuffer.h"
 #include "webp/encode.h"
 
-typedef int (*WebPImporter)(WebPPicture* const, const uint8_t* const data, int rowStride);
-
 namespace blink {
 
 static int writeOutput(const uint8_t* data, size_t size, const WebPPicture* const picture)
 {
-    static_cast<Vector<unsigned char>*>(picture->custom_ptr)->append(data, size);
-    return 1;
+    return static_cast<Vector<unsigned char>*>(picture->custom_ptr)->append(data, size), 1;
 }
 
-static bool rgbPictureImport(const unsigned char* pixels, WebPImporter importRGB, WebPPicture* picture)
+inline bool importUnpremultipliedRGBA(const unsigned char* pixels, WebPPicture* picture)
 {
-    // Write the RGB pixels to an rgb data buffer, alpha premultiplied, then import the rgb data.
-
-    size_t pixelCount = picture->height * picture->width;
-
-    OwnPtr<unsigned char[]> rgb = adoptArrayPtr(new unsigned char[pixelCount * 3]);
-    if (!rgb.get())
-        return false;
-
-    for (unsigned char* data = rgb.get(); pixelCount-- > 0; pixels += 4) {
-        unsigned char alpha = pixels[3];
-        if (alpha != 255) {
-            *data++ = SkMulDiv255Round(pixels[0], alpha);
-            *data++ = SkMulDiv255Round(pixels[1], alpha);
-            *data++ = SkMulDiv255Round(pixels[2], alpha);
-        } else {
-            *data++ = pixels[0];
-            *data++ = pixels[1];
-            *data++ = pixels[2];
-        }
-    }
-
-    return importRGB(picture, rgb.get(), picture->width * 3);
+    return WebPPictureImportRGBA(picture, pixels, picture->width * 4);
 }
 
-static bool encodePixels(IntSize imageSize, const unsigned char* pixels, int quality, Vector<unsigned char>* output)
+static bool encodePixels(IntSize imageSize, const unsigned char* pixels, int quality, Vector<unsigned char>* output, WEBPImageEncoder::Mode mode)
 {
     if (imageSize.width() <= 0 || imageSize.width() > WEBP_MAX_DIMENSION)
         return false;
@@ -88,25 +64,38 @@ static bool encodePixels(IntSize imageSize, const unsigned char* pixels, int qua
     picture.width = imageSize.width();
     picture.height = imageSize.height();
 
-    if (!rgbPictureImport(pixels, &WebPPictureImportRGB, &picture))
+    if (quality > 99 || mode == WEBPImageEncoder::Lossless)
+        config.lossless = picture.use_argb = 1;
+
+    if (!importUnpremultipliedRGBA(pixels, &picture))
         return false;
 
     picture.custom_ptr = output;
     picture.writer = &writeOutput;
-    config.quality = quality;
-    config.method = 3;
+
+    if (mode == WEBPImageEncoder::Lossless) {
+        config.quality = quality;
+        config.method = 2;
+    } else if (quality > 99) {
+        config.quality = 75;
+        config.method = 0;
+    } else {
+        ASSERT(!config.lossless);
+        config.quality = quality;
+        config.method = 3;
+    }
 
     bool success = WebPEncode(&config, &picture);
     WebPPictureFree(&picture);
     return success;
 }
 
-bool WEBPImageEncoder::encode(const ImageDataBuffer& imageData, int quality, Vector<unsigned char>* output)
+bool WEBPImageEncoder::encode(const ImageDataBuffer& imageData, int quality, Vector<unsigned char>* output, WEBPImageEncoder::Mode mode)
 {
     if (!imageData.pixels())
         return false;
 
-    return encodePixels(IntSize(imageData.width(), imageData.height()), imageData.pixels(), quality, output);
+    return encodePixels(IntSize(imageData.width(), imageData.height()), imageData.pixels(), quality, output, mode);
 }
 
 } // namespace blink