SkScaledCodec class

src/codec/SkSwizzler.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSwizzler_DEFINED
 #define SkSwizzler_DEFINED
 
@@ skipping 104 matching lines @@
     /**
      *  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 dst Destination to write pixels. Must match info and dstRowBytes
      *  @param dstRowBytes rowBytes for dst.
      *  @param ZeroInitialized Whether dst is zero-initialized. The
                                implementation may choose to skip writing zeroes
      *                         if set to kYes_ZeroInitialized.
+     *  @param sampleX the step between samples in the x direction.

[scroggo, 2015/07/28 15:58:10]

As stated elsewhere, I think we should consider combining this with
ZeroInitialized, and just pass the Options object.

[emmaleer, 2015/07/29 21:55:08]

SampleX is no longer needed to be stored in the options object, so I left this
as is.

      *  @return A new SkSwizzler or NULL on failure.
      */
     static SkSwizzler* CreateSwizzler(SrcConfig, const SkPMColor* ctable,
                                       const SkImageInfo&, void* dst,
                                       size_t dstRowBytes,
-                                      SkCodec::ZeroInitialized);
+                                      SkCodec::ZeroInitialized, int sampleX);
 
     /**
      * Fill the remainder of the destination with a single color
      *
      * @param dstStartRow
      * The destination row to fill from.
      *
      * @param numRows
      * The number of rows to fill.
      *
@@ skipping 97 matching lines @@
     const RowProc       fRowProc;
     const SkPMColor*    fColorTable;      // Unowned pointer
     const int           fDeltaSrc;        // if bitsPerPixel % 8 == 0
                                           //     deltaSrc is bytesPerPixel
                                           // else
                                           //     deltaSrc is bitsPerPixel
     const SkImageInfo   fDstInfo;
     void*               fDstRow;
     const size_t        fDstRowBytes;
     int                 fCurrY;
+    int                 fX0;              // first X coord to sample
+    int                 fSampleX;         // step between X samples

[scroggo, 2015/07/28 15:58:10]

This can now be const.

fX0 can also be const, if you initialize it in the intializer list like so:

fX0(sampleX == 1 ? 0 : sampleX >> 1)

On a related note, I thought we needed to check to make sure the sample size was
not too big. Do we do that elsewhere?

[emmaleer, 2015/07/29 21:55:08]

SampleX is set to srcWidth / dstWidth in initializeSwizzler, so will never be
too big

 
     SkSwizzler(RowProc proc, const SkPMColor* ctable, int deltaSrc,
-               const SkImageInfo& info, void* dst, size_t rowBytes);
+               const SkImageInfo& info, void* dst, size_t rowBytes, int sampleX);
 
 };
 #endif // SkSwizzler_DEFINED