Provides multiple implementations of Android's SkBitmapRegionDecoder

src/utils/SkBitmapRegionDecoder.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 "SkBitmapRegionCanvas.h"
+#include "SkBitmapRegionDecoder.h"
+#include "SkBitmapRegionSampler.h"
+#include "SkScanlineDecoder.h"
+#include "SkImageDecoder.h"
+
+SkBitmapRegionDecoder* SkBitmapRegionDecoder::CreateBitmapRegionDecoder(
+        SkStreamRewindable* stream, Strategy strategy) {
+    switch (strategy) {
+        case kOriginal_Strategy: {
+            SkImageDecoder* decoder = SkImageDecoder::Factory(stream);
+            int width, height;
+            if (nullptr == decoder) {
+                SkDebugf("Error: Could not create image decoder.\n");
+                return nullptr;
+            }
+            if (!decoder->buildTileIndex(stream, &width, &height)) {
+                SkDebugf("Error: Could not build tile index.\n");
+                delete decoder;
+                return nullptr;
+            }
+            return new SkBitmapRegionSampler(decoder, width, height);
+        }
+        case kCanvas_Strategy: {
+            SkScanlineDecoder* decoder = SkScanlineDecoder::NewFromStream(stream);
+            if (nullptr == decoder) {
+                SkDebugf("Error: Failed to create decoder.\n");
+                return nullptr;
+            }
+            switch (decoder->getScanlineOrder()) {
+                case SkScanlineDecoder::kTopDown_SkScanlineOrder:
+                case SkScanlineDecoder::kNone_SkScanlineOrder:
+                    break;
+                default:
+                    SkDebugf("Error: Scanline ordering not supported.\n");
+                    return nullptr;
+            }
+            return new SkBitmapRegionCanvas(decoder);
+        }
+        default:
+            SkASSERT(false);
+            return nullptr;
+    }
+}