SkScaledCodec class

src/codec/SkSwizzler.h

Index: src/codec/SkSwizzler.h
diff --git a/src/codec/SkSwizzler.h b/src/codec/SkSwizzler.h
index 76ca74877a391c9670ef8f71d68a8ed8ad131e52..8d9ea83cc2321b606ba63898496d3c9aa91ee9f1 100644
--- a/src/codec/SkSwizzler.h
+++ b/src/codec/SkSwizzler.h
@@ -115,16 +115,18 @@ public:
     /**
      *  Create a new SkSwizzler.
      *  @param SrcConfig Description of the format of the source.
-     *  @param SkImageInfo dimensions() describe both the src and the dst.
-     *              Other fields describe the dst.
+     *  @param dstInfo describes the destination.
      *  @param ZeroInitialized Whether dst is zero-initialized. The
                                implementation may choose to skip writing zeroes
      *                         if set to kYes_ZeroInitialized.
+     *  @param srcWidth is the width of the source. Used to calculate the width samplesize. 
+     *  Width sampling is supported by the swizzler, by skipping pixels when swizzling the row.

[scroggo, 2015/07/31 19:31:58]

Maybe this should also explain why we chose to support width sampling, but not
height? Something like "sampling in Y can be done by a client with a scanline
decoder, but sampling in X allows the swizzler to skip swizzling pixels and
reading from and writing to memory."

nit: this should be indented. (I do not have a strong preference for how much,
and I am not sure whether our guides tell us.)

[emmaleer, 2015/07/31 20:43:10]

Acknowledged.

+     *  Height sampling is not supported by the swizzler, but is implemented in SkScaledCodec.
      *  @return A new SkSwizzler or NULL on failure.
      */
     static SkSwizzler* CreateSwizzler(SrcConfig, const SkPMColor* ctable,
-                                      const SkImageInfo&, SkCodec::ZeroInitialized);
-
+                                      const SkImageInfo& dstInfo, SkCodec::ZeroInitialized, 
+                                      int srcWidth);
     /**
      * Fill the remainder of the destination with a single color
      *
@@ -197,9 +199,10 @@ private:
                                           //     deltaSrc is bitsPerPixel
     const SkImageInfo   fDstInfo;
     int                 fCurrY;
+    const int           fX0;              // first X coord to sample
+    const int           fSampleX;         // step between X samples
 
-    SkSwizzler(RowProc proc, const SkPMColor* ctable, int deltaSrc,
-               const SkImageInfo& info);
-
+    SkSwizzler(RowProc proc, const SkPMColor* ctable, int deltaSrc, const SkImageInfo& info, 
+               int sampleX);
 };
 #endif // SkSwizzler_DEFINED