Handle gray alpha conversions in SkSwizzler

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
 
 #include "SkCodec.h"
 #include "SkColor.h"
 #include "SkImageInfo.h"
 #include "SkSampler.h"
 
 class SkSwizzler : public SkSampler {
 public:
     /**
      *  Enum describing the config of the source data.
      */
     enum SrcConfig {
         kUnknown,  // Invalid type.
         kBit,      // A single bit to distinguish between white and black.
         kGray,
+        kGrayAlpha,
         kIndex1,
         kIndex2,
         kIndex4,
         kIndex,
         kRGB,
         kBGR,
         kBGRX,     // The alpha channel can be anything, but the image is opaque.
         kRGBA,
         kBGRA,
         kCMYK,
@@ skipping 13 matching lines @@
             case kIndex1:
                 return 1;
             case kIndex2:
                 return 2;
             case kIndex4:
                 return 4;
             case kGray:
             case kIndex:
             case kNoOp8:
                 return 8;
+            case kGrayAlpha:
             case kNoOp16:
                 return 16;
             case kRGB:
             case kBGR:
                 return 24;
             case kRGBA:
             case kBGRX:
             case kBGRA:
             case kCMYK:
             case kNoOp32:
@@ skipping 87 matching lines @@
                             const uint8_t* SK_RESTRICT src,
                             int dstWidth, int bpp, int deltaSrc, int offset,
                             const SkPMColor ctable[]);
 
     template <RowProc Proc>
     static void SkipLeading8888ZerosThen(void* SK_RESTRICT dstRow,
                                          const uint8_t* SK_RESTRICT src,
                                          int dstWidth, int bpp, int deltaSrc, int offset,
                                          const SkPMColor ctable[]);
 
+    template <RowProc Proc>
+    static void SkipLeadingGrayAlphaZerosThen(void* dst, const uint8_t* src, int width, int bpp,
+                                              int deltaSrc, int offset, const SkPMColor ctable[]);
+
     // May be NULL.  We have not implemented optimized functions for all supported transforms.
     const RowProc       fFastProc;
     // Always non-NULL.  Supports sampling.
     const RowProc       fSlowProc;
     // The actual RowProc we are using.  This depends on if fFastProc is non-NULL and
     // whether or not we are sampling.
     RowProc             fActualProc;
 
     const SkPMColor*    fColorTable;      // Unowned pointer
 
@@ skipping 81 matching lines @@
                                           //     fBPP is bitsPerPixel
     const int           fDstBPP;          // Bytes per pixel for the destination color type
 
     SkSwizzler(RowProc fastProc, RowProc proc, const SkPMColor* ctable, int srcOffset,
             int srcWidth, int dstOffset, int dstWidth, int srcBPP, int dstBPP);
 
     int onSetSampleX(int) override;
 
 };
 #endif // SkSwizzler_DEFINED