Provides multiple implementations of Android's SkBitmapRegionDecoder

src/utils/SkBitmapRegionSampler.cpp

Index: src/utils/SkBitmapRegionSampler.cpp
diff --git a/src/utils/SkBitmapRegionSampler.cpp b/src/utils/SkBitmapRegionSampler.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..2306ccd2ad76cb604b69299e12939f9c287087c4
--- /dev/null
+++ b/src/utils/SkBitmapRegionSampler.cpp
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "SkBitmapRegionSampler.h"
+
+SkBitmapRegionSampler::SkBitmapRegionSampler(SkImageDecoder* decoder, int width, 
+                                             int height)
+    : INHERITED(width, height)
+    , fDecoder(decoder)
+{}
+
+/*
+ * This has several key differences from the Android version:
+ *     Returns a Skia bitmap instead of an Android bitmap.
+ *     Android version attempts to reuse a recycled bitmap.
+ *     Removed the options object and used parameters for color type and
+ *     sample size.
+ */
+SkBitmap* SkBitmapRegionSampler::decodeRegion(int start_x, int start_y,
+                                              int width, int height,
+                                              int sampleSize,
+                                              SkColorType prefColorType) {
+
+    fDecoder->setDitherImage(true);

[scroggo, 2015/08/13 16:53:07]

Why did you choose these settings?

[msarett, 2015/08/13 18:10:23]

These are Android's default settings.  Adding a comment.

+    fDecoder->setPreferQualityOverSpeed(false);
+    fDecoder->setRequireUnpremultipliedColors(false);
+    fDecoder->setSampleSize(sampleSize);
+    SkIRect region;

[scroggo, 2015/08/13 16:53:07]

nit: a blank line before this line would be helpful

[msarett, 2015/08/13 18:10:23]

Done.

+    region.fLeft = start_x;
+    region.fTop = start_y;
+    region.fRight = start_x + width;
+    region.fBottom = start_y + height;
+
+    SkAutoTDelete<SkBitmap> bitmap(new SkBitmap());
+    if (!fDecoder->decodeSubset(bitmap.get(), region, prefColorType)) {
+        SkDebugf("Error: decodeRegion failed.\n");
+        return NULL;
+    }
+    return bitmap.detach();
+}