Refactor SkBitmapRegionDecoderInterface for Android

tools/SkBitmapRegionSampler.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 "SkBitmapRegionSampler.h"
 #include "SkCodecPriv.h"
 
 SkBitmapRegionSampler::SkBitmapRegionSampler(SkImageDecoder* decoder, int width, 
                                              int height)
     : INHERITED(width, height)
     , fDecoder(decoder)
 {}
 
-/*
- * Three 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) {
-    // Match Android's default settings
+bool SkBitmapRegionSampler::prepareRegion(const SkIRect& desiredSubset,
+                                          int sampleSize,
+                                          SkColorType dstColorType,
+                                          bool requireUnpremul,
+                                          SkImageInfo* outInfo) {
     fDecoder->setDitherImage(true);
     fDecoder->setPreferQualityOverSpeed(false);
-    fDecoder->setRequireUnpremultipliedColors(false);
+    fDecoder->setRequireUnpremultipliedColors(requireUnpremul);
     fDecoder->setSampleSize(sampleSize);
 
+    fSubset = desiredSubset;
+
     // kAlpha8 is the legacy representation of kGray8 used by SkImageDecoder
-    if (kGray_8_SkColorType == prefColorType) {
-        prefColorType = kAlpha_8_SkColorType;
+    if (kGray_8_SkColorType == dstColorType) {
+        dstColorType = kAlpha_8_SkColorType;

[scroggo, 2015/10/27 15:00:51]

note that we'll need to update the glue code in Android, which requests
kAlpha_8. We also may want to update it so that it reports ALPHA_8 (in Java) if
we end up with a bitmap that is kAlpha_8.

+    }
+    fColorType = dstColorType;
+    return true;
+}
+
+bool SkBitmapRegionSampler::decodeRegion(SkBitmap& bitmap) {
+    if (fSubset.isEmpty()) {
+        SkCodecPrintf("Error: Call prepareRegion() first.");
+        return false;
     }
 
-    SkIRect region;
-    region.fLeft = start_x;
-    region.fTop = start_y;
-    region.fRight = start_x + width;
-    region.fBottom = start_y + height;
+    if (!fDecoder->decodeSubset(&bitmap, fSubset, fColorType)) {
+        SkCodecPrintf("Error: decodeRegion failed.\n");
+        return false;
+    }
 
-    SkAutoTDelete<SkBitmap> bitmap(new SkBitmap());
-    if (!fDecoder->decodeSubset(bitmap.get(), region, prefColorType)) {
-        SkCodecPrintf("Error: decodeRegion failed.\n");
-        return nullptr;
-    }
-    return bitmap.detach();
+    return true;
 }