Adds an iOS implementation of gfx::Image.

ui/gfx/image/image_ios.mm

Index: ui/gfx/image/image_ios.mm
diff --git a/ui/gfx/image/image_ios.mm b/ui/gfx/image/image_ios.mm
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+// Copyright 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 <UIKit/UIKit.h>
+
+#include "base/logging.h"
+#include "base/memory/scoped_nsobject.h"
+#include "ui/gfx/image/image_skia.h"
+#include "ui/gfx/image/image_skia_util_ios.h"
+
+namespace gfx {
+namespace internal {
+
+void PNGFromUIImage(UIImage* uiimage, std::vector<unsigned char>* png) {
+  NSData* data = UIImagePNGRepresentation(uiimage);
+
+  if ([data length] == 0)
+    return;
+
+  png->resize([data length]);
+  [data getBytes:&png->at(0) length:[data length]];
+}
+
+UIImage* CreateUIImageFromPNG(const std::vector<unsigned char>& png) {
+  NSData* data = [NSData dataWithBytes:&png.front() length:png.size()];
+  scoped_nsobject<UIImage> image ([[UIImage alloc] initWithData:data]);
+  if (!image) {
+    LOG(WARNING) << "Unable to decode PNG into UIImage.";
+    // Return a 16x16 red image to visually show error.
+    UIGraphicsBeginImageContext(CGSizeMake(16, 16));
+    CGContextRef context = UIGraphicsGetCurrentContext();
+    CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
+    CGContextFillRect(context, CGRectMake(0.0, 0.0, 16, 16));
+    image.reset([UIGraphicsGetImageFromCurrentImageContext() retain]);
+    UIGraphicsEndImageContext();
+  }
+  return image.release();
+}
+
+void PNGFromImageSkia(const ImageSkia* skia, std::vector<unsigned char>* png) {
+  // iOS does not expose libpng, so conversion from ImageSkia to PNG must go
+  // through UIImage.
+  // TODO(rohitrao): Rewrite the callers of this function to save the UIImage
+  // representation in the gfx::Image.  If we're generating it, we might as well
+  // hold on to it.
+  UIImage* image = UIImageFromImageSkia(*skia);
+  PNGFromUIImage(image, png);
+}
+
+ImageSkia* ImageSkiaFromPNG(const std::vector<unsigned char>& png) {
+  // iOS does not expose libpng, so conversion from PNG to ImageSkia must go
+  // through UIImage.
+  scoped_nsobject<UIImage> uiimage(CreateUIImageFromPNG(png));
+  if (!uiimage) {
+    LOG(WARNING) << "Unable to decode PNG into ImageSkia.";
+    // Return a 16x16 red image to visually show error.
+    SkBitmap bitmap;
+    bitmap.setConfig(SkBitmap::kARGB_8888_Config, 16, 16);
+    bitmap.allocPixels();
+    bitmap.eraseRGB(0xff, 0, 0);
+    return new ImageSkia(bitmap);
+  }
+
+  return new ImageSkia(ImageSkiaFromUIImage(uiimage));
+}
+
+} // namespace internal
+} // namespace gfx