Scanline decoding for bmp

src/codec/SkBmpMaskCodec.cpp

Index: src/codec/SkBmpMaskCodec.cpp
diff --git a/src/codec/SkBmpMaskCodec.cpp b/src/codec/SkBmpMaskCodec.cpp
index 1c89ba1c84de158d80efa8725aebeef6d6b6c68c..daedbac166ba0530fff9ce73f716e155e80b4569 100644
--- a/src/codec/SkBmpMaskCodec.cpp
+++ b/src/codec/SkBmpMaskCodec.cpp
@@ -46,10 +46,9 @@ SkCodec::Result SkBmpMaskCodec::onGetPixels(const SkImageInfo& dstInfo,
         return kInvalidConversion;
     }
 
-    // Initialize a the mask swizzler
-    if (!this->initializeSwizzler(dstInfo)) {
-        SkCodecPrintf("Error: cannot initialize swizzler.\n");
-        return kInvalidConversion;
+    Result result = this->prepareToDecode(dstInfo, opts, inputColorPtr, inputColorCount);
+    if (kSuccess != result) {
+        return result;
     }
 
     return this->decode(dstInfo, dst, dstRowBytes, opts);
@@ -100,7 +99,7 @@ SkCodec::Result SkBmpMaskCodec::decode(const SkImageInfo& dstInfo,
         }
 
         // Decode the row in destination format
-        int row = SkBmpCodec::kBottomUp_RowOrder == this->rowOrder() ? height - 1 - y : y;
+        uint32_t row = this->getDstRow(y);
         void* dstRow = SkTAddOffset<void>(dst, row * dstRowBytes);
         fMaskSwizzler->swizzle(dstRow, srcRow);
     }
@@ -108,3 +107,14 @@ SkCodec::Result SkBmpMaskCodec::decode(const SkImageInfo& dstInfo,
     // Finished decoding the entire image
     return kSuccess;
 }
+
+SkCodec::Result SkBmpMaskCodec::prepareToDecode(const SkImageInfo& dstInfo,
+        const SkCodec::Options& options, SkPMColor inputColorPtr[], int* inputColorCount) {
+    // Initialize a the mask swizzler
+    if (!this->initializeSwizzler(dstInfo)) {
+        SkCodecPrintf("Error: cannot initialize swizzler.\n");
+        return SkCodec::kInvalidConversion;
+    }
+
+    return SkCodec::kSuccess;
+}