Make BitmapRegionDecoder succeed on invalid requests

src/android/SkBitmapRegionCodec.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 "SkBitmapRegionCodec.h"
 #include "SkBitmapRegionDecoderPriv.h"
 #include "SkCodecPriv.h"
 #include "SkPixelRef.h"
 
 SkBitmapRegionCodec::SkBitmapRegionCodec(SkAndroidCodec* codec)
     : INHERITED(codec->getInfo().width(), codec->getInfo().height())
     , fCodec(codec)
 {}
 
 bool SkBitmapRegionCodec::decodeRegion(SkBitmap* bitmap, SkBRDAllocator* allocator,
-        const SkIRect& desiredSubset, int sampleSize, SkColorType dstColorType,
+        const SkIRect& desiredSubset, int sampleSize, SkColorType prefColorType,
         bool requireUnpremul) {
 
     // Fix the input sampleSize if necessary.
     if (sampleSize < 1) {
         sampleSize = 1;
     }
 
     // The size of the output bitmap is determined by the size of the
     // requested subset, not by the size of the intersection of the subset
     // and the image dimensions.
@@ skipping 12 matching lines @@
     }
 
     // Ask the codec for a scaled subset
     if (!fCodec->getSupportedSubset(&subset)) {
         SkCodecPrintf("Error: Could not get subset.\n");
         return false;
     }
     SkISize scaledSize = fCodec->getSampledSubsetDimensions(sampleSize, subset);
 
     // Create the image info for the decode
-    SkAlphaType dstAlphaType = fCodec->getInfo().alphaType();
-    if (kOpaque_SkAlphaType != dstAlphaType) {
-        dstAlphaType = requireUnpremul ? kUnpremul_SkAlphaType : kPremul_SkAlphaType;
-    }
+    SkColorType dstColorType = fCodec->computeOutputColorType(prefColorType);
+    SkAlphaType dstAlphaType = fCodec->computeOutputAlphaType(requireUnpremul);
     SkImageInfo decodeInfo = SkImageInfo::Make(scaledSize.width(), scaledSize.height(),
             dstColorType, dstAlphaType);
 
     // Construct a color table for the decode if necessary
     SkAutoTUnref<SkColorTable> colorTable(nullptr);
     SkPMColor* colorPtr = nullptr;
     int* colorCountPtr = nullptr;
     int maxColors = 256;
     SkPMColor colors[256];
     if (kIndex_8_SkColorType == dstColorType) {
@@ skipping 20 matching lines @@
         scaledOutY = outY / sampleSize;
         // We need to be safe here because getSupportedSubset() may have modified the subset.
         const int extraX = SkTMax(0, desiredSubset.width() - outX - subset.width());
         const int extraY = SkTMax(0, desiredSubset.height() - outY - subset.height());
         const int scaledExtraX = extraX / sampleSize;
         const int scaledExtraY = extraY / sampleSize;
         scaledOutWidth += scaledOutX + scaledExtraX;
         scaledOutHeight += scaledOutY + scaledExtraY;
     }
     SkImageInfo outInfo = decodeInfo.makeWH(scaledOutWidth, scaledOutHeight);
+    if (kGray_8_SkColorType == dstColorType) {
+        // The legacy implementations of BitmapFactory and BitmapRegionDecoder
+        // used kAlpha8 for grayscale images (before kGray8 existed).  While
+        // the codec recognizes kGray8, we need to decode into a kAlpha8
+        // bitmap in order to avoid a behavior change.
+        outInfo = SkImageInfo::MakeA8(scaledOutWidth, scaledOutHeight);
+    }
     bitmap->setInfo(outInfo);
     if (!bitmap->tryAllocPixels(allocator, colorTable.get())) {
         SkCodecPrintf("Error: Could not allocate pixels.\n");
         return false;
     }
 
     // Zero the bitmap if the region is not completely within the image.
     // TODO (msarett): Can we make this faster by implementing it to only
     //                 zero parts of the image that we won't overwrite with
     //                 pixels?
@@ skipping 31 matching lines @@
 
     return true;
 }
 
 bool SkBitmapRegionCodec::conversionSupported(SkColorType colorType) {
     // FIXME: Call virtual function when it lands.
     SkImageInfo info = SkImageInfo::Make(0, 0, colorType, fCodec->getInfo().alphaType(),
             fCodec->getInfo().profileType());
     return conversion_possible(info, fCodec->getInfo());
 }