Make BitmapRegionDecoder succeed on invalid requests

src/codec/SkAndroidCodec.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 "SkAndroidCodec.h"
 #include "SkCodec.h"
 #include "SkCodecPriv.h"
@@ skipping 31 matching lines @@
 }
 
 SkAndroidCodec* SkAndroidCodec::NewFromData(SkData* data, SkPngChunkReader* chunkReader) {
     if (!data) {
         return nullptr;
     }
 
     return NewFromStream(new SkMemoryStream(data), chunkReader);
 }
 
+SkColorType SkAndroidCodec::computeOutputColorType(SkColorType requestedColorType) {
+    SkColorType suggestedColorType = this->getInfo().colorType();
+    switch (requestedColorType) {
+        case kARGB_4444_SkColorType:
+        case kN32_SkColorType:
+            return kN32_SkColorType;
+        case kIndex_8_SkColorType:
+            if (kIndex_8_SkColorType == suggestedColorType) {
+                return kIndex_8_SkColorType;
+            }
+            break;
+        case kAlpha_8_SkColorType:
+            // Fall through to kGray_8.  Before kGray_8_SkColorType existed,
+            // we allowed clients to request kAlpha_8 when they wanted a
+            // grayscale decode.
+        case kGray_8_SkColorType:
+            if (kGray_8_SkColorType == suggestedColorType) {
+                return kGray_8_SkColorType;
+            }
+            break;
+        case kRGB_565_SkColorType:
+            if (kOpaque_SkAlphaType == this->getInfo().alphaType()) {
+                return kRGB_565_SkColorType;
+            }
+            break;
+        default:
+            break;
+    }
+
+    return suggestedColorType;
+}
+
+SkAlphaType SkAndroidCodec::computeOutputAlphaType(bool requestedUnpremul) {
+    if (kOpaque_SkAlphaType == this->getInfo().alphaType()) {
+        return kOpaque_SkAlphaType;
+    }
+    return requestedUnpremul ? kUnpremul_SkAlphaType : kPremul_SkAlphaType;
+}
+
 SkISize SkAndroidCodec::getSampledDimensions(int sampleSize) const {
     if (!is_valid_sample_size(sampleSize)) {
         return SkISize::Make(0, 0);
     }
 
     // Fast path for when we are not scaling.
     if (1 == sampleSize) {
         return fInfo.dimensions();
     }
 
@@ skipping 59 matching lines @@
         }
     }
 
     return this->onGetAndroidPixels(info, pixels, rowBytes, *options);
 }
 
 SkCodec::Result SkAndroidCodec::getAndroidPixels(const SkImageInfo& info, void* pixels,
         size_t rowBytes) {
     return this->getAndroidPixels(info, pixels, rowBytes, nullptr);
 }