Add support for transparent/translucent pixels in the user image

components/user_manager/user_image/user_image.cc

 // Copyright 2014 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 "components/user_manager/user_image/user_image.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/trace_event/trace_event.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/codec/jpeg_codec.h"
+#include "ui/gfx/codec/png_codec.h"
+#include "ui/gfx/geometry/size.h"
 
 namespace user_manager {
 
 namespace {
 
 // Default quality for encoding user images.
 const int kDefaultEncodingQuality = 90;
 
 }  // namespace
 
 // static
 scoped_refptr<base::RefCountedBytes> UserImage::Encode(
-    const SkBitmap& bitmap) {
+    const SkBitmap& bitmap,
+    ImageFormat image_format) {
   TRACE_EVENT2("oobe", "UserImage::Encode",
                "width", bitmap.width(), "height", bitmap.height());
   SkAutoLockPixels lock_bitmap(bitmap);
   std::vector<unsigned char> output;
-  if (gfx::JPEGCodec::Encode(
-          reinterpret_cast<unsigned char*>(bitmap.getAddr32(0, 0)),
-          gfx::JPEGCodec::FORMAT_SkBitmap,
-          bitmap.width(),
-          bitmap.height(),
-          bitmap.width() * bitmap.bytesPerPixel(),
-          kDefaultEncodingQuality, &output)) {
-    return base::RefCountedBytes::TakeVector(&output);
+  auto* bitmap_data = reinterpret_cast<unsigned char*>(bitmap.getAddr32(0, 0));
+  if (image_format == FORMAT_JPEG) {
+    if (gfx::JPEGCodec::Encode(
+            bitmap_data,
+            gfx::JPEGCodec::FORMAT_SkBitmap,
+            bitmap.width(),
+            bitmap.height(),
+            bitmap.width() * bitmap.bytesPerPixel(),
+            kDefaultEncodingQuality, &output)) {
+      return base::RefCountedBytes::TakeVector(&output);
+    }
+  } else if (image_format == FORMAT_PNG) {
+    if (gfx::PNGCodec::Encode(
+            bitmap_data,
+            gfx::PNGCodec::FORMAT_SkBitmap,
+            gfx::Size(bitmap.width(), bitmap.height()),
+            bitmap.width() * bitmap.bytesPerPixel(),
+            false,  // discard_transparency
+            std::vector<gfx::PNGCodec::Comment>(), &output)) {
+      return base::RefCountedBytes::TakeVector(&output);
+    }
   } else {
-    return nullptr;
+    LOG(FATAL) << "Invalid image format: " << image_format;
   }
+  return nullptr;
 }
 
 // static
 std::unique_ptr<UserImage> UserImage::CreateAndEncode(
-    const gfx::ImageSkia& image) {
+    const gfx::ImageSkia& image,
+    ImageFormat image_format) {
   if (image.isNull())
     return base::WrapUnique(new UserImage);
 
-  scoped_refptr<base::RefCountedBytes> image_bytes = Encode(*image.bitmap());
+  scoped_refptr<base::RefCountedBytes> image_bytes = Encode(*image.bitmap(),
+                                                            image_format);
   if (image_bytes) {
-    std::unique_ptr<UserImage> result(new UserImage(image, image_bytes));
+    std::unique_ptr<UserImage> result(
+        new UserImage(image, image_bytes, image_format));
     result->MarkAsSafe();
     return result;
   }
   return base::WrapUnique(new UserImage(image));
 }
 
+// static
+UserImage::ImageFormat UserImage::ChooseImageFormat(const SkBitmap& bitmap) {
+  return SkBitmap::ComputeIsOpaque(bitmap) ? FORMAT_JPEG : FORMAT_PNG;
+}
+
 UserImage::UserImage() {
 }
 
 UserImage::UserImage(const gfx::ImageSkia& image)
     : image_(image) {
 }
 
 UserImage::UserImage(const gfx::ImageSkia& image,
-                     scoped_refptr<base::RefCountedBytes> image_bytes)
+                     scoped_refptr<base::RefCountedBytes> image_bytes,
+                     ImageFormat image_format)
     : image_(image),
-      image_bytes_(image_bytes) {
+      image_bytes_(image_bytes),
+      image_format_(image_format) {
 }
 
 UserImage::~UserImage() {}
 
 void UserImage::MarkAsSafe() {
   is_safe_format_ = true;
 }
 
 }  // namespace user_manager