Implement SkEncodeImage()

ui/gfx/codec/install_skia_codec.cc

+// Copyright (c) 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 "ui/gfx/codec/install_skia_codec.h"
+
+#include "base/synchronization/lock.h"
+#include "skia/ext/skia_encode_image.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkEncodedImageFormat.h"
+#include "third_party/skia/include/core/SkStream.h"
+#include "ui/gfx/codec/jpeg_codec.h"
+#include "ui/gfx/codec/png_codec.h"
+#include "ui/gfx/geometry/size.h"
+
+static bool Encode(SkWStream* dst,
+                   const SkPixmap& pixmap,
+                   SkEncodedImageFormat format,
+                   int quality) {
+  if (kN32_SkColorType != pixmap.colorType() ||
+      (kPremul_SkAlphaType != pixmap.alphaType() &&
+       kOpaque_SkAlphaType != pixmap.alphaType())) {
+    return false;
+  }
+  std::vector<unsigned char> buffer;
+  switch (format) {
+    case SkEncodedImageFormat::kPNG:
+      return gfx::PNGCodec::Encode(
+                 reinterpret_cast<const unsigned char*>(pixmap.addr()),
+                 gfx::PNGCodec::FORMAT_SkBitmap,
+                 gfx::Size(pixmap.width(), pixmap.height()),
+                 static_cast<int>(pixmap.rowBytes()), false,
+                 std::vector<gfx::PNGCodec::Comment>(), &buffer) &&
+             !buffer.empty() &&
+             dst->write(&buffer[0], buffer.size());
+    case SkEncodedImageFormat::kJPEG:
+      return gfx::JPEGCodec::Encode(
+                 reinterpret_cast<const unsigned char*>(pixmap.addr()),
+                 gfx::JPEGCodec::FORMAT_SkBitmap, pixmap.width(),
+                 pixmap.height(), static_cast<int>(pixmap.rowBytes()), quality,
+                 &buffer) &&
+             !buffer.empty() &&
+             dst->write(&buffer[0], buffer.size());
+    default:
+      return false;
+  }
+}
+
+void gfx::InstallCodecsIntoSkia() {
+  // FIXME:  What is the chromium version of SkOnce?
+  static base::Lock lock;

[dcheng, 2016/12/01 06:22:38]

Unfortunately, this doesn't work.

Our lock implementation is not considered a POD, thus the C++ style guide does
not permit this:
https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables

Furthermore, we don't enable thread-safe statics in Chromium, so the
initialization of base::Lock itself is racy.

It's OK to have some sort of DCHECK static bool, but I do not think we should
have it in the general path: initialization should be well-defined, and a DCHECK
should be sufficient to guard.

[hal.canary, 2016/12/20 16:51:13]

Okay.  I have removed this for now.  

+  static bool g_done = false;
+  base::AutoLock autoLock(lock);
+  if (!g_done) {
+    skia::SetImageEncoder(&Encode);
+    g_done = true;
+  }
+}