Add support for PNG representation in gfx::Image

ui/gfx/image/image_mac.mm

+// Copyright (c) 2012 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/image/image.h"
+
+#import <AppKit/AppKit.h>
+
+#include "base/logging.h"
+#include "base/memory/scoped_nsobject.h"
+
+namespace gfx {
+namespace internal {
+
+void PNGFromNSImage(NSImage* nsimage, std::vector<unsigned char>* png) {
+  CGImageRef cg_image = [nsimage CGImageForProposedRect:NULL
+                                                context:nil
+                                                  hints:nil];
+  scoped_nsobject<NSBitmapImageRep> ns_bitmap(
+      [[NSBitmapImageRep alloc] initWithCGImage:cg_image]);
+  NSData* ns_data = [ns_bitmap representationUsingType:NSPNGFileType
+                                            properties:nil];
+  const unsigned char* bytes =
+      static_cast<const unsigned char*>([ns_data bytes]);
+  png->assign(bytes, bytes + [ns_data length]);
+}
+
+NSImage* NSImageFromPNG(const std::vector<unsigned char>& png) {
+  scoped_nsobject<NSData> ns_data(
+      [[NSData alloc] initWithBytes:&png.front() length:png.size()]);
+  scoped_nsobject<NSImage> image([[NSImage alloc] initWithData:ns_data]);
+  if (!image) {
+    LOG(WARNING) << "Unable to decode PNG.";
+    // Return a 16x16 red image to visually show error.
+    image.reset([[NSImage alloc] initWithSize:NSMakeSize(16, 16)]);
+    [image lockFocus];
+    [[NSColor colorWithDeviceRed:1.0 green:0.0 blue:0.0 alpha:1.0] set];
+    NSRectFill(NSMakeRect(0, 0, 16, 16));

[Robert Sesek, 2012/07/31 14:07:17]

nit: you could declare this rect as a local, and then use rect.size as the param
to |-initWithSize:| to be DRY

[cjhopman, 2012/08/03 22:15:25]

Done.

+    [image unlockFocus];
+  }
+  return image.release();
+}
+
+} // namespace internal
+} // namespace gfx
+