Introduce the image_decoder service

services/image_decoder/image_decoder_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "chrome/utility/image_decoder_impl.h"
+#include "services/image_decoder/image_decoder_impl.h"
 
 #include <string.h>
 
 #include <utility>
 
 #include "base/logging.h"
 #include "content/public/child/image_decoder_utils.h"
-#include "ipc/ipc_channel.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "skia/ext/image_operations.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/geometry/size.h"
 
 #if defined(OS_CHROMEOS)
 #include "ui/gfx/chromeos/codec/jpeg_codec_robust_slow.h"
 #include "ui/gfx/codec/png_codec.h"
 #endif
 
+namespace image_decoder {
+
 namespace {
-int64_t kMaxMessageSize = IPC::Channel::kMaximumMessageSize;
+
 int64_t kPadding = 64;
-}
 
-ImageDecoderImpl::ImageDecoderImpl() : ImageDecoderImpl(kMaxMessageSize) {}
+}  // namespace
 
-ImageDecoderImpl::ImageDecoderImpl(int64_t max_message_size)
-    : max_message_size_(max_message_size) {}
+ImageDecoderImpl::ImageDecoderImpl(
+    std::unique_ptr<service_manager::ServiceContextRef> service_ref)
+    : service_ref_(std::move(service_ref)) {}
 
-ImageDecoderImpl::~ImageDecoderImpl() {
-}
+ImageDecoderImpl::~ImageDecoderImpl() = default;
 
 void ImageDecoderImpl::DecodeImage(const std::vector<uint8_t>& encoded_data,
                                    mojom::ImageCodec codec,
                                    bool shrink_to_fit,
+                                   int64_t max_size_in_bytes,
                                    const DecodeImageCallback& callback) {
-  if (encoded_data.empty()) {
+  if (encoded_data.size() == 0) {
     callback.Run(SkBitmap());
     return;
   }
 
   SkBitmap decoded_image;
 #if defined(OS_CHROMEOS)
   if (codec == mojom::ImageCodec::ROBUST_JPEG) {
     // Our robust jpeg decoding is using IJG libjpeg.
-    std::unique_ptr<SkBitmap> decoded_jpeg(gfx::JPEGCodecRobustSlow::Decode(
-        encoded_data.data(), encoded_data.size()));
-    if (decoded_jpeg.get() && !decoded_jpeg->empty())
-      decoded_image = *decoded_jpeg;
+    if (encoded_data.size()) {
+      std::unique_ptr<SkBitmap> decoded_jpeg(gfx::JPEGCodecRobustSlow::Decode(
+          encoded_data.data(), encoded_data.size()));
+      if (decoded_jpeg.get() && !decoded_jpeg->empty())
+        decoded_image = *decoded_jpeg;
+    }
   } else if (codec == mojom::ImageCodec::ROBUST_PNG) {
     // Our robust PNG decoding is using libpng.
-    SkBitmap decoded_png;
-    if (gfx::PNGCodec::Decode(encoded_data.data(), encoded_data.size(),
-                              &decoded_png)) {
-      decoded_image = decoded_png;
+    if (encoded_data.size()) {
+      SkBitmap decoded_png;
+      if (gfx::PNGCodec::Decode(
+            encoded_data.data(), encoded_data.size(), &decoded_png)) {
+        decoded_image = decoded_png;
+      }
     }
   }
 #endif  // defined(OS_CHROMEOS)
   if (codec == mojom::ImageCodec::DEFAULT) {
-    decoded_image = content::DecodeImage(encoded_data.data(), gfx::Size(),
-                                         encoded_data.size());
+    decoded_image = content::DecodeImage(
+        encoded_data.data(), gfx::Size(), encoded_data.size());
   }
 
   if (!decoded_image.isNull()) {
     // When serialized, the space taken up by a skia::mojom::Bitmap excluding
     // the pixel data payload should be:
     //   sizeof(skia::mojom::Bitmap::Data_) + pixel data array header (8 bytes)
     // Use a bigger number in case we need padding at the end.
     int64_t struct_size = sizeof(skia::mojom::Bitmap::Data_) + kPadding;
     int64_t image_size = decoded_image.computeSize64();
     int halves = 0;
-    while (struct_size + (image_size >> 2 * halves) > max_message_size_)
+    while (struct_size + (image_size >> 2 * halves) > max_size_in_bytes)
       halves++;
     if (halves) {
+      // If the decoded image is too large, either discard it or shrink it.
+      //
+      // TODO(rockot): Also support exposing the bytes via shared memory for
+      // larger images. https://crbug.com/416916.
       if (shrink_to_fit) {
-        // If decoded image is too large for IPC message, shrink it by halves.
-        // This prevents quality loss, and should never overshrink on displays
-        // smaller than 3600x2400.
-        // TODO (Issue 416916): Instead of shrinking, return via shared memory
+        // Shrinking by halves prevents quality loss and should never overshrink
+        // on displays smaller than 3600x2400.
         decoded_image = skia::ImageOperations::Resize(
             decoded_image, skia::ImageOperations::RESIZE_LANCZOS3,
             decoded_image.width() >> halves, decoded_image.height() >> halves);
       } else {
         decoded_image.reset();
       }
     }
   }
 
   callback.Run(decoded_image);
 }
+
+}  // namespace image_decoder