Add support for encoding/decoding WebP images.

blimp/common/compositor/blimp_image_serialization_processor.cc

Index: blimp/common/compositor/blimp_image_serialization_processor.cc
diff --git a/blimp/common/compositor/blimp_image_serialization_processor.cc b/blimp/common/compositor/blimp_image_serialization_processor.cc
index 36ea6af38275856c8d91fe02215e0c2b4c2b9db0..6c1032a12903b6eb53e0676eeab1473bfef93dfe 100644
--- a/blimp/common/compositor/blimp_image_serialization_processor.cc
+++ b/blimp/common/compositor/blimp_image_serialization_processor.cc
@@ -8,14 +8,89 @@
 #include <vector>
 
 #include "base/logging.h"
+#include "blimp/common/compositor/webp_decoder.h"
+#include "third_party/libwebp/webp/encode.h"
+#include "third_party/skia/include/core/SkData.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "third_party/skia/include/core/SkPixelSerializer.h"
 
 namespace {
-bool NoopDecoder(const void* input, size_t input_size, SkBitmap* bitmap) {
-  // TODO(nyquist): Add an image decoder.
-  return false;
-}
+// TODO(nyquist): Make sure encoder does not serialize images more than once.
+// See crbug.com/548434.
+class WebPImageEncoder : public SkPixelSerializer {
+ public:
+  WebPImageEncoder() {}
+  ~WebPImageEncoder() override{};
+
+  bool onUseEncodedData(const void* data, size_t len) override {
+    const unsigned char* cast_data = static_cast<const unsigned char*>(data);
+    if (len < 14)
+      return false;
+    return !memcmp(cast_data, "RIFF", 4) && !memcmp(cast_data + 8, "WEBPVP", 6);
+  }
+
+  SkData* onEncode(const SkPixmap& pixmap) override {
+    auto pixel_chars = static_cast<const unsigned char*>(pixmap.addr());
+    WebPConfig config;
+    if (!WebPConfigInit(&config))
+      return nullptr;
+    WebPPicture picture;
+    if (!WebPPictureInit(&picture))
+      return nullptr;
+
+    if (!pixmap.width() || pixmap.width() > WEBP_MAX_DIMENSION)
+      return nullptr;
+    picture.width = pixmap.width();
+    if (!pixmap.height() || pixmap.height() > WEBP_MAX_DIMENSION)
+      return nullptr;
+    picture.height = pixmap.height();
+
+    if (!PlatformImportPicture(pixel_chars, &picture))
+      return nullptr;
+
+    const int quality = 50;
+    std::vector<unsigned char> data;
+    picture.custom_ptr = &data;
+    picture.writer = &WebPImageEncoder::WriteOutput;
+    config.quality = quality;
+    config.method = 3;
+
+    bool success = WebPEncode(&config, &picture);
+    WebPPictureFree(&picture);
+    if (!success)
+      return nullptr;
+    return SkData::NewWithCopy(&data.front(), data.size());
+  }
+
+ private:
+  static int WriteOutput(const uint8_t* data,
+                         size_t size,
+                         const WebPPicture* const picture) {
+    std::vector<unsigned char>* dest =
+        static_cast<std::vector<unsigned char>*>(picture->custom_ptr);
+    dest->insert(dest->end(), data, data + size);
+    return 1;
+  }
+
+  typedef int (*WebPImporter)(WebPPicture* const,
+                              const uint8_t* const data,
+                              int row_stride);
+
+  bool RgbPictureImport(const unsigned char* pixels,
+                        WebPImporter import_RGBA,
+                        WebPPicture* picture) {
+    return import_RGBA(picture, pixels, static_cast<int>(picture->width * 4)) !=
+           0;
+  }
+
+  bool PlatformImportPicture(const unsigned char* pixels,
+                             WebPPicture* picture) {
+    if (SK_B32_SHIFT)  // Android
+      return RgbPictureImport(pixels, &WebPPictureImportRGBA, picture);

[urvang, 2016/02/13 00:24:36]

WebPPictureImportRGBA() and WebPPictureImportBGRA() both assume that RGB is NOT
premultiplied by alpha, actually.

So, you should assume both in encoder and decoder that you are using
non-premultiplied mode.

[nyquist, 2016/02/16 23:37:10]

Always assuming premultiplied, and applying unpremultiplication on the fly.

+
+    return RgbPictureImport(pixels, &WebPPictureImportBGRA, picture);
+  }
+};
 
 }  // namespace
 
@@ -24,12 +99,12 @@ namespace blimp {
 BlimpImageSerializationProcessor::BlimpImageSerializationProcessor(Mode mode) {
   switch (mode) {
     case Mode::SERIALIZATION:
-      pixel_serializer_ = nullptr;
+      pixel_serializer_.reset(new WebPImageEncoder);
       pixel_deserializer_ = nullptr;
       break;
     case Mode::DESERIALIZATION:
       pixel_serializer_ = nullptr;
-      pixel_deserializer_ = &NoopDecoder;
+      pixel_deserializer_ = &WebPDecoder;
       break;
     default:
       NOTREACHED() << "Unknown serialization mode";