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,

[Robert Sesek, 2012/09/13 16:14:24]

nit: continuations are indented 4 from the previous line

[rohitrao (ping after 24h), 2012/09/13 17:57:57]

Done.

[rohitrao (ping after 24h), 2012/09/13 17:57:57]

Done.

+                          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

[Robert Sesek, 2012/09/13 16:14:24]

There was a discussion about the threaded usage of gfx::Image on chromium-dev a
few weeks ago.

[rohitrao (ping after 24h), 2012/09/13 17:57:57]

There was an assertion that ImageSkia is currently not thread-safe, and soon
will be even less thread-safe, and then it devolved into a discussion about
which threads it was safe to load images on.

I will probably come back to this and replace it with CG calls, but I want to
get favicons working first so that I can visually see if I screw up flippedness
=)

(Plus the mac code is already not thread-safe.)

+  // calls setCurrentContext, so it's similarly limited to the main thread.
+  DCHECK([NSThread isMainThread]);
+  UIGraphicsPushContext(context);

[Robert Sesek, 2012/09/13 16:14:24]

I'm surprised you guys don't have a scoper for this.

[rohitrao (ping after 24h), 2012/09/13 17:57:57]

I didn't see one in any of the obvious places.  I've made myself a note to
upstream one and use it as needed.

[stuartmorgan, 2012/09/14 11:01:37]

Did you check in ui/gfx/scoped_ui_graphics_push_context_ios.h? ;)

+  [image drawInRect:CGRectMake(0, 0, size.width, size.height)
+          blendMode:kCGBlendModeCopy
+              alpha:1.0];
+  UIGraphicsPopContext();
+
+  return bitmap;
+}
+
+UIImage* SkBitmapToUIImageWithColorSpace(const SkBitmap& skiaBitmap,
+                                         CGColorSpaceRef colorSpace) {

[Robert Sesek, 2012/09/13 16:14:24]

naming: color_space and throughout

[rohitrao (ping after 24h), 2012/09/13 17:57:57]

Done.

+  if (skiaBitmap.isNull())
+    return nil;
+
+  // First convert SkBitmap to CGImageRef.
+  base::mac::ScopedCFTypeRef<CGImageRef> cgimage(
+      SkCreateCGImageRefWithColorspace(skiaBitmap, colorSpace));
+
+  // Now convert to NSImage.
+  // TODO(rohitrao): Gotta incorporate the scale factor somewhere!
+  return [UIImage imageWithCGImage:cgimage.get()];
+}
+
+UIImage* SkBitmapToUIImage(const SkBitmap& skiaBitmap) {
+  base::mac::ScopedCFTypeRef<CGColorSpaceRef> colorSpace(
+      CGColorSpaceCreateDeviceRGB());
+  return SkBitmapToUIImageWithColorSpace(skiaBitmap, colorSpace.get());
+}
+
+
+}  // namespace gfx