DM: find max component difference

dm/DMUtil.h

 #ifndef DMUtil_DEFINED
 #define DMUtil_DEFINED
 
 #include "SkBenchmark.h"
 #include "SkBitmap.h"
 #include "SkString.h"
 #include "gm_expectations.h"
 
 class SkBBHFactory;
 
@@ skipping 10 matching lines @@
                          SkBBHFactory* factory = NULL);
 
 // Allocate an empty bitmap with this size and depth.
 void AllocatePixels(SkColorType, int w, int h, SkBitmap* bitmap);
 // Allocate an empty bitmap the same size and depth as reference.
 void AllocatePixels(const SkBitmap& reference, SkBitmap* bitmap);
 
 // Draw picture to bitmap.
 void DrawPicture(SkPicture* picture, SkBitmap* bitmap);
 
+// What is the maximum component difference in these bitmaps?
+unsigned MaxComponentDifference(const SkBitmap& a, const SkBitmap& b);

[reed1, 2014/05/16 12:30:00]

For the future, it might prove useful to return 4 values, one for each
component, as that may be interesting to the operator. Not for this CL per-se.

[mtklein, 2014/05/16 13:00:53]

Agreed.

+
 // Are these identical bitmaps?
 bool BitmapsEqual(const SkBitmap& a, const SkBitmap& b);
 
 }  // namespace DM
 
 #endif  // DMUtil_DEFINED