Add support for PNG representation in gfx::Image

ui/gfx/image/image.h

Index: ui/gfx/image/image.h
diff --git a/ui/gfx/image/image.h b/ui/gfx/image/image.h
index c03db3ad18e783231e57e53712350e10e925f0c6..a780922a5102c2d2045d8ecceb6be843542dc7a5 100644
--- a/ui/gfx/image/image.h
+++ b/ui/gfx/image/image.h
@@ -36,6 +36,7 @@ class ImageMacTest;
 }
 
 namespace gfx {
+class ImagePNG;

[Robert Sesek, 2012/07/20 21:03:01]

Remove

[cjhopman, 2012/07/24 01:44:13]

Done.

 class ImageSkia;
 class ImageSkiaRep;
 
@@ -55,6 +56,7 @@ class UI_EXPORT Image {
     kImageRepCocoa,
     kImageRepCairo,
     kImageRepSkia,
+    kImageRepPNG,
   };
 
   typedef std::map<RepresentationType, internal::ImageRep*> RepresentationMap;
@@ -62,6 +64,11 @@ class UI_EXPORT Image {
   // Creates an empty image with no representations.
   Image();
 
+  // Creates a new image by copying the png-encoded input for use as the default
+  // representation.
+  Image(const unsigned char* png, size_t input_size);
+  explicit Image(const std::vector<unsigned char>& png);

[Robert Sesek, 2012/07/20 21:03:01]

I wonder if you even need this constructor. A client that has a vector can
always use .front() and .size() to the constructor above.

What do you think?

[cjhopman, 2012/07/24 01:44:13]

Agreed. Done.

+
   // Creates a new image by copying the ImageSkia for use as the default
   // representation.
   explicit Image(const ImageSkia& image);
@@ -98,6 +105,7 @@ class UI_EXPORT Image {
   // Converts the Image to the desired representation and stores it internally.
   // The returned result is a weak pointer owned by and scoped to the life of
   // the Image.
+  const std::vector<unsigned char>* ToImagePNG() const;

[Robert Sesek, 2012/07/20 21:03:01]

I'm wondering if this should return a const ref. Reasons against are that it's a
difference in the API from all the other To*() functions, and it makes it easier
to perform a vector copy.

[cjhopman, 2012/07/24 01:44:13]

I think my preference would be to keep it consistent with the other To*()
functions, but I'm not really opposed to changing it if you'd prefer it as a
reference.

[Robert Sesek, 2012/07/24 18:59:17]

Agree. Let's keep these as pointers.

   const SkBitmap* ToSkBitmap() const;
   const ImageSkia* ToImageSkia() const;
 #if defined(TOOLKIT_GTK)
@@ -113,6 +121,7 @@ class UI_EXPORT Image {
   // backing pixels are shared amongst all copies (a fact of each of the
   // converted representations, rather than a limitation imposed by Image) and
   // so the result should be considered immutable.
+  std::vector<unsigned char>* CopyImagePNG() const;
   ImageSkia* CopyImageSkia() const;
   SkBitmap* CopySkBitmap() const;
 #if defined(TOOLKIT_GTK)