Add the method isOpaque() to SkImage

src/image/SkImage_Codec.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageDecoder.h"
 #include "SkImage_Base.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkData.h"
 
 class SkImage_Codec : public SkImage_Base {
 public:
     static SkImage* NewEmpty();
 
     SkImage_Codec(SkData* encodedData, int width, int height);
     virtual ~SkImage_Codec();
 
     virtual void onDraw(SkCanvas*, SkScalar, SkScalar, const SkPaint*) SK_OVERRIDE;
     virtual void onDrawRectToRect(SkCanvas*, const SkRect*, const SkRect&, const SkPaint*) SK_OVERRIDE;
 
+    virtual bool isOpaque() const SK_OVERRIDE;
+
 private:
     SkData*     fEncodedData;
     SkBitmap    fBitmap;
 
     typedef SkImage_Base INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImage_Codec::SkImage_Codec(SkData* data, int width, int height) : INHERITED(width, height) {
@@ skipping 32 matching lines @@
     }
 
     SkBitmap bitmap;
     if (!SkImageDecoder::DecodeMemory(data->bytes(), data->size(), &bitmap, kUnknown_SkColorType,
                                       SkImageDecoder::kDecodeBounds_Mode)) {
         return NULL;
     }
 
     return SkNEW_ARGS(SkImage_Codec, (data, bitmap.width(), bitmap.height()));
 }
+
+
+bool SkImage_Codec::isOpaque() const {
+    if (!fBitmap.pixelRef()) {
+        return SkImage::isOpaque();

[reed1, 2014/07/18 20:50:02]

This will return false, even if the bitmap is opaque.

The absence of a pixelref for this image can just mean that we haven't decoded
the image *yet*

[Rémi Piotaix, 2014/07/18 21:12:50]

Yep.
I made this method const so SkImageDecoder::DecodeMemory() can't be called like
in other methods of SkImage_Codec.

Should i remove the 'const' attribute (or make fBitmap mutable ?)

[scroggo, 2014/07/18 21:39:14]

It does seem to me that fBitmap is logically mutable.

Might there be a situation where a client wants to know the opacity, but does
not want to necessarily decode yet?

+    }
+
+    return fBitmap.isOpaque();
+}