Implementation of SkBitmapRegionDecoder using SkAndroidCodec

tools/SkBitmapRegionCanvas.cpp

Index: tools/SkBitmapRegionCanvas.cpp
diff --git a/tools/SkBitmapRegionCanvas.cpp b/tools/SkBitmapRegionCanvas.cpp
index 7226e044e75c82a77b908a39d33d9d3281bcc50a..f7083e623d643924be4eea6cb5cb20c50ac10216 100644
--- a/tools/SkBitmapRegionCanvas.cpp
+++ b/tools/SkBitmapRegionCanvas.cpp
@@ -16,30 +16,6 @@ SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* decoder)
 {}
 
 /*
- * Chooses the correct image subset offsets and dimensions for the partial decode.

[msarett, 2015/10/12 18:42:36]

Moved to SkCodecTools.h

The only change is that this is now "inline" instead of "static".

- *
- * @return true if the subset is completely contained within the image
- *         false otherwise
- */
-static bool set_subset_region(int inputOffset, int inputDimension,
-        int imageOriginalDimension, int* imageSubsetOffset, int* outOffset,
-        int* imageSubsetDimension) {
-
-    // This must be at least zero, we can't start decoding the image at a negative coordinate.
-    *imageSubsetOffset = SkTMax(0, inputOffset);
-
-    // If inputOffset is less than zero, we decode to an offset location in the output bitmap.
-    *outOffset = *imageSubsetOffset - inputOffset;
-
-    // Use imageSusetOffset to make sure we don't decode pixels past the edge of the image.
-    // Use outOffset to make sure we don't decode pixels past the edge of the region.
-    *imageSubsetDimension = SkTMin(imageOriginalDimension - *imageSubsetOffset,
-            inputDimension - *outOffset);
-
-    return (*outOffset == 0) && (*imageSubsetDimension == inputDimension);
-}
-
-/*
  * Three differences from the Android version:
  *     Returns a Skia bitmap instead of an Android bitmap.
  *     Android version attempts to reuse a recycled bitmap.
@@ -56,6 +32,11 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
         return nullptr;
     }
 
+    // Fix the input sampleSize if necessary.

[msarett, 2015/10/12 18:42:36]

Android does not set a default sampleSize.  We should fix this is Android, but
also catch it here to be robust.

+    if (sampleSize < 1) {
+        sampleSize = 1;
+    }
+
     // The client may not necessarily request a region that is fully within
     // the image.  We may need to do some calculation to determine what part
     // of the image to decode.
@@ -108,7 +89,7 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     }
     SkImageInfo decodeInfo = SkImageInfo::Make(this->width(), this->height(),
             dstColorType, dstAlphaType);
-    
+
     // Start the scanline decoder
     SkCodec::Result r = fDecoder->startScanlineDecode(decodeInfo);
     if (SkCodec::kSuccess != r) {
@@ -152,7 +133,7 @@ SkBitmap* SkBitmapRegionCanvas::decodeRegion(int inputX, int inputY,
     // TODO (msarett): This could be skipped if memory is zero initialized.
     //                 This would matter if this code is moved to Android and
     //                 uses Android bitmaps.
-    if (imageContainsEntireSubset) {
+    if (!imageContainsEntireSubset) {

[msarett, 2015/10/12 18:42:36]

Oops.

         bitmap->eraseColor(0);
     }