Support more swizzles to 565 in SkCodec

src/codec/SkBmpStandardCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBmpStandardCodec.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
 #include "SkScanlineDecoder.h"
 #include "SkStream.h"
 
 /*
- * Checks if the conversion between the input image and the requested output
- * image has been implemented
- */
-static bool conversion_possible(const SkImageInfo& dst,
-                                const SkImageInfo& src) {
-    // Ensure that the profile type is unchanged
-    if (dst.profileType() != src.profileType()) {
-        return false;
-    }
-
-    // Ensure the alpha type is valid
-    if (!valid_alpha(dst.alphaType(), src.alphaType())) {
-        return false;
-    }
-
-    // Check for supported color types
-    switch (dst.colorType()) {
-        // Allow output to kN32 from any type of input
-        case kN32_SkColorType:
-            return true;
-        // Allow output to kIndex_8 from compatible inputs
-        case kIndex_8_SkColorType:
-            return kIndex_8_SkColorType == src.colorType();
-        default:
-            return false;
-    }
-}
-
-/*
  * Creates an instance of the decoder
  * Called only by NewFromStream
  */
 SkBmpStandardCodec::SkBmpStandardCodec(const SkImageInfo& info, SkStream* stream,
                                        uint16_t bitsPerPixel, uint32_t numColors,
                                        uint32_t bytesPerColor, uint32_t offset,
                                        SkBmpCodec::RowOrder rowOrder, bool inIco)
     : INHERITED(info, stream, bitsPerPixel, rowOrder)
     , fColorTable(NULL)
     , fNumColors(this->computeNumColors(numColors))
@@ skipping 262 matching lines @@
         } else {
             row = height - 1 - y;
         }
 
         void* dstRow = SkTAddOffset<void>(dst, row * dstRowBytes);
         fSwizzler->swizzle(dstRow, fSrcBuffer.get());
     }
 
     // Finally, apply the AND mask for bmp-in-ico images
     if (fInIco) {
+        // BMP in ICO have transparency, so this cannot be 565, and this mask
+        // prevents us from using kIndex8. The below code depends on the output
+        // being an SkPMColor.
+        SkASSERT(dstInfo.colorType() == kN32_SkColorType);
+
         // The AND mask is always 1 bit per pixel
         const size_t rowBytes = SkAlign4(compute_row_bytes(width, 1));
 
         SkPMColor* dstPtr = (SkPMColor*) dst;
         for (int y = 0; y < height; y++) {
             // The srcBuffer will at least be large enough
             if (stream()->read(fSrcBuffer.get(), rowBytes) != rowBytes) {
                 SkCodecPrintf("Warning: incomplete AND mask for bmp-in-ico.\n");
                 return kIncompleteInput;
             }
@@ skipping 16 matching lines @@
                 uint32_t alphaBit =
                         (fSrcBuffer.get()[quotient] >> shift) & 0x1;
                 dstRow[x] &= alphaBit - 1;
             }
         }
     }
 
     // Finished decoding the entire image
     return kSuccess;
 }