Scanline decoding for bmp

src/codec/SkBmpStandardCodec.cpp

Index: src/codec/SkBmpStandardCodec.cpp
diff --git a/src/codec/SkBmpStandardCodec.cpp b/src/codec/SkBmpStandardCodec.cpp
index 27cea4ead0e816a9d5f77e3abba484e0c633050f..631d86abcd87f3a0b65ea1d7003a44565a29d586 100644
--- a/src/codec/SkBmpStandardCodec.cpp
+++ b/src/codec/SkBmpStandardCodec.cpp
@@ -53,20 +53,9 @@ SkCodec::Result SkBmpStandardCodec::onGetPixels(const SkImageInfo& dstInfo,
         return kInvalidConversion;
     }
 
-    // Create the color table if necessary and prepare the stream for decode
-    // Note that if it is non-NULL, inputColorCount will be modified
-    if (!this->createColorTable(dstInfo.alphaType(), inputColorCount)) {
-        SkCodecPrintf("Error: could not create color table.\n");
-        return kInvalidInput;
-    }
-
-    // Copy the color table to the client if necessary
-    copy_color_table(dstInfo, fColorTable, inputColorPtr, inputColorCount);
-
-    // Initialize a swizzler if necessary
-    if (!this->initializeSwizzler(dstInfo, opts)) {
-        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);
@@ -170,7 +159,8 @@ SkCodec::Result SkBmpStandardCodec::onGetPixels(const SkImageInfo& dstInfo,
 bool SkBmpStandardCodec::initializeSwizzler(const SkImageInfo& dstInfo,
                                             const Options& opts) {
     // Allocate space for a row buffer
-    const size_t rowBytes = SkAlign4(compute_row_bytes(dstInfo.width(), this->bitsPerPixel()));
+    const size_t rowBytes = SkAlign4(compute_row_bytes(this->getInfo().width(),
+            this->bitsPerPixel()));
     fSrcBuffer.reset(SkNEW_ARRAY(uint8_t, rowBytes));
 
     // Get swizzler configuration
@@ -251,10 +241,10 @@ static uint32_t get_fill_color_or_index(uint16_t bitsPerPixels, SkAlphaType alph
  * Performs the bitmap decoding for standard input format
  */
 SkCodec::Result SkBmpStandardCodec::decode(const SkImageInfo& dstInfo,
-                                   void* dst, size_t dstRowBytes,
-                                   const Options& opts) {
+                                           void* dst, size_t dstRowBytes,
+                                           const Options& opts) {
     // Set constant values
-    const int width = dstInfo.width();
+    const int width = this->getInfo().width();
     const int height = dstInfo.height();
     const size_t rowBytes = SkAlign4(compute_row_bytes(width, this->bitsPerPixel()));
 
@@ -281,12 +271,7 @@ SkCodec::Result SkBmpStandardCodec::decode(const SkImageInfo& dstInfo,
         }
 
         // Decode the row in destination format
-        uint32_t row;
-        if (SkBmpCodec::kTopDown_RowOrder == this->rowOrder()) {
-            row = y;
-        } else {
-            row = height - 1 - y;
-        }
+        uint32_t row = this->getDstRow(y);
 
         void* dstRow = SkTAddOffset<void>(dst, row * dstRowBytes);
         fSwizzler->swizzle(dstRow, fSrcBuffer.get());
@@ -310,12 +295,7 @@ SkCodec::Result SkBmpStandardCodec::decode(const SkImageInfo& dstInfo,
                 return kIncompleteInput;
             }
 
-            int row;
-            if (SkBmpCodec::kBottomUp_RowOrder == this->rowOrder()) {
-                row = height - y - 1;
-            } else {
-                row = y;
-            }
+            int row = this->getDstRow(y);
 
             SkPMColor* dstRow =
                     SkTAddOffset<SkPMColor>(dstPtr, row * dstRowBytes);
@@ -335,3 +315,23 @@ SkCodec::Result SkBmpStandardCodec::decode(const SkImageInfo& dstInfo,
     // Finished decoding the entire image
     return kSuccess;
 }
+
+SkCodec::Result SkBmpStandardCodec::prepareToDecode(const SkImageInfo& dstInfo,
+        const SkCodec::Options& options, SkPMColor inputColorPtr[], int* inputColorCount) {
+    // Create the color table if necessary and prepare the stream for decode
+    // Note that if it is non-NULL, inputColorCount will be modified
+    if (!this->createColorTable(dstInfo.alphaType(), inputColorCount)) {
+        SkCodecPrintf("Error: could not create color table.\n");
+        return SkCodec::kInvalidInput;
+    }
+
+    // Copy the color table to the client if necessary
+    copy_color_table(dstInfo, this->fColorTable, inputColorPtr, inputColorCount);
+
+    // Initialize a swizzler if necessary
+    if (!this->initializeSwizzler(dstInfo, options)) {
+        SkCodecPrintf("Error: cannot initialize swizzler.\n");
+        return SkCodec::kInvalidConversion;
+    }
+    return SkCodec::kSuccess;
+}