SkScaledCodec class

src/codec/SkSwizzler.h

Index: src/codec/SkSwizzler.h
diff --git a/src/codec/SkSwizzler.h b/src/codec/SkSwizzler.h
index 2fab7f66b6ea15184c3618304a012a9b4bf4df1c..6272d81194e3841937fc46923fe89c7edb8f8732 100644
--- a/src/codec/SkSwizzler.h
+++ b/src/codec/SkSwizzler.h
@@ -117,16 +117,22 @@ 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. Height sampling is not supported by the swizzler, 
+                        but is implemented in SkScaledCodec.
+                        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.
      *  @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
      *
@@ -185,11 +191,13 @@ private:
      *  @param deltaSrc if bitsPerPixel % 8 == 0, deltaSrc is bytesPerPixel
      *                  else, deltaSrc is bitsPerPixel
      *  @param ctable Colors (used for kIndex source).
+     *  @param offset The offset before the first pixel to sample.
+                        Is in bytes or bits based on what deltaSrc is in.
      */
     typedef ResultAlpha (*RowProc)(void* SK_RESTRICT dstRow,
                                    const uint8_t* SK_RESTRICT src,
                                    int width, int deltaSrc,
-                                   const SkPMColor ctable[]);
+                                   const SkPMColor ctable[], int offset);

[scroggo, 2015/08/07 19:39:49]

nit: I might change the order, so it's next to deltaSrc.

(on the other hand, that change is kind of repetitive without a whole lot of
benefit...)

[emmaleer, 2015/08/11 20:10:36]

Acknowledged.

 
     const RowProc       fRowProc;
     const SkPMColor*    fColorTable;      // Unowned pointer
@@ -199,9 +207,10 @@ 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