respect srgb gamma when building mips

src/core/SkMipMap.h

Index: src/core/SkMipMap.h
diff --git a/src/core/SkMipMap.h b/src/core/SkMipMap.h
index 5cb4ea8ce670b30c90eec35455b65befd5c65d0c..fba6d07386eb5b25aab746137416506c32835cdc 100644
--- a/src/core/SkMipMap.h
+++ b/src/core/SkMipMap.h
@@ -12,6 +12,7 @@
 #include "SkPixmap.h"
 #include "SkScalar.h"
 #include "SkSize.h"
+#include "SkShader.h"
 
 class SkBitmap;
 class SkDiscardableMemory;
@@ -20,8 +21,18 @@ typedef SkDiscardableMemory* (*SkDiscardableFactoryProc)(size_t bytes);
 
 class SkMipMap : public SkCachedData {
 public:
-    static SkMipMap* Build(const SkPixmap& src, SkDiscardableFactoryProc);
-    static SkMipMap* Build(const SkBitmap& src, SkDiscardableFactoryProc);
+    enum SrcGammaMode {
+        kIgnore_SrcGammaMode,   // treat src as having linear gamma
+        kRespect_SrcGammaMode,  // treat src as described by its SkColorSpace
+    };
+
+    static SkMipMap* Build(const SkPixmap& src, SrcGammaMode, SkDiscardableFactoryProc);
+    static SkMipMap* Build(const SkBitmap& src, SrcGammaMode, SkDiscardableFactoryProc);
+
+    static SrcGammaMode DeduceMode(const SkShader::ContextRec& rec) {
+        return (SkShader::ContextRec::kPMColor_DstType == rec.fPreferredDstType) ?

[msarett, 2016/06/03 16:54:17]

We will never want to respect gamma with kPMColor_DstType?

[reed1, 2016/06/07 16:01:10]

That is the policy I'm proposing:
- if the target is L32, we never respect gamma (or gamets)
- if the target is S32 or F16, we always respect gamma (etc.)

+                                kIgnore_SrcGammaMode : kRespect_SrcGammaMode;
+    }
 
     // Determines how many levels a SkMipMap will have without creating that mipmap.
     static int ComputeLevelCount(int baseWidth, int baseHeight);
@@ -44,10 +55,10 @@ protected:
     }
 
 private:
-    Level*  fLevels;
-    int     fCount;
+    sk_sp<SkColorSpace> fCS;
+    Level*              fLevels;    // managed by the baseclass, may be null due to onDataChanged.
+    int                 fCount;
 
-    // we take ownership of levels, and will free it with sk_free()
     SkMipMap(void* malloc, size_t size) : INHERITED(malloc, size) {}
     SkMipMap(size_t size, SkDiscardableMemory* dm) : INHERITED(size, dm) {}