Adds an iOS implementation of gfx::Image.

skia/ext/skia_utils_ios.mm

+// 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 "skia/ext/skia_utils_ios.h"
+
+#import <UIKit/UIKit.h>
+
+#include "base/logging.h"
+#include "base/mac/scoped_cftyperef.h"
+#include "third_party/skia/include/utils/mac/SkCGUtils.h"
+
+namespace gfx {
+
+SkBitmap UIImageToSkBitmap(UIImage* image, CGSize size, bool is_opaque) {
+  SkBitmap bitmap;
+  if (!image)
+    return bitmap;
+
+  bitmap.setConfig(SkBitmap::kARGB_8888_Config, size.width, size.height);
+  if (!bitmap.allocPixels())
+    return bitmap;
+
+  bitmap.setIsOpaque(is_opaque);
+  void* data = bitmap.getPixels();
+
+  // Allocate a bitmap context with 4 components per pixel (BGRA). Apple
+  // recommends these flags for improved CG performance.
+#define HAS_ARGB_SHIFTS(a, r, g, b) \
+            (SK_A32_SHIFT == (a) && SK_R32_SHIFT == (r) \
+             && SK_G32_SHIFT == (g) && SK_B32_SHIFT == (b))
+#if defined(SK_CPU_LENDIAN) && HAS_ARGB_SHIFTS(24, 16, 8, 0)
+  base::mac::ScopedCFTypeRef<CGColorSpaceRef> color_space(
+      CGColorSpaceCreateDeviceRGB());
+  base::mac::ScopedCFTypeRef<CGContextRef> context(
+      CGBitmapContextCreate(data, size.width, size.height, 8, size.width*4,
+                            color_space,
+                            kCGImageAlphaPremultipliedFirst |
+                                kCGBitmapByteOrder32Host));
+#else
+#error We require that Skia's and CoreGraphics's recommended \
+       image memory layout match.
+#endif
+#undef HAS_ARGB_SHIFTS
+
+  DCHECK(context);
+  if (!context)
+    return bitmap;
+
+  // UIGraphicsPushContext be called from the main thread.
+  // TODO(rohitrao): We can use CG to make this thread safe, but the mac code
+  // calls setCurrentContext, so it's similarly limited to the main thread.
+  DCHECK([NSThread isMainThread]);
+  UIGraphicsPushContext(context);
+  [image drawInRect:CGRectMake(0, 0, size.width, size.height)
+          blendMode:kCGBlendModeCopy
+              alpha:1.0];
+  UIGraphicsPopContext();
+
+  return bitmap;
+}
+
+UIImage* SkBitmapToUIImageWithColorSpace(const SkBitmap& skia_bitmap,
+                                         CGColorSpaceRef color_space) {
+  if (skia_bitmap.isNull())
+    return nil;
+
+  // First convert SkBitmap to CGImageRef.
+  base::mac::ScopedCFTypeRef<CGImageRef> cg_image(
+      SkCreateCGImageRefWithColorspace(skia_bitmap, color_space));
+
+  // Now convert to UIImage.
+  // TODO(rohitrao): Gotta incorporate the scale factor somewhere!
+  return [UIImage imageWithCGImage:cg_image.get()];
+}
+
+}  // namespace gfx