Make BitmapRegionDecoder succeed on invalid requests

src/android/SkBitmapRegionCanvas.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 "SkBitmapRegionDecoderPriv.h"
 #include "SkCanvas.h"
 #include "SkCodecPriv.h"
 
 SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkCodec* decoder)
     : INHERITED(decoder->getInfo().width(), decoder->getInfo().height())
     , fDecoder(decoder)
 {}
 
 bool SkBitmapRegionCanvas::decodeRegion(SkBitmap* bitmap, SkBRDAllocator* allocator,
         const SkIRect& desiredSubset, int sampleSize, SkColorType dstColorType,
         bool requireUnpremul) {
+    // FIXME: This class works well as a performance/quality comparison for

[scroggo, 2015/12/09 20:57:31]

Maybe this should be in the header?

[msarett, 2015/12/10 15:19:26]

Done.

+    //        SkBitmapRegionCodec, but it lacks several capabilities that are
+    //        required by BitmapRegionDecoder in Android.
+    //        (1) Decodes to kGray8 and kIndex8.
+    //        (2) Decodes to kUnpremul.
+    //        (3) Correcting an invalid dstColorType.  For example, if the
+    //            client requests kRGB_565 for a non-opaque image, rather than
+    //            fail, we need to go ahead and decode to kN32.
+
     // Reject color types not supported by this method
     if (kIndex_8_SkColorType == dstColorType || kGray_8_SkColorType == dstColorType) {
         SkCodecPrintf("Error: Color type not supported.\n");
         return false;
     }
 
     // Reject requests for unpremultiplied alpha
     if (requireUnpremul) {
         SkCodecPrintf("Error: Alpha type not supported.\n");
         return false;
     }
     SkAlphaType dstAlphaType = fDecoder->getInfo().alphaType();
     if (kUnpremul_SkAlphaType == dstAlphaType) {
         dstAlphaType = kPremul_SkAlphaType;
     }
 
-    // FIXME: Can we add checks and support kIndex8 or unpremultiplied alpha in special cases?
-
     // 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.
     // If inputX is negative, we will need to place decoded pixels into the
     // output bitmap starting at a left offset.  Call this outX.
@@ skipping 82 matching lines @@
     // SkCanvas does not draw to these color types.
     if (kIndex_8_SkColorType == colorType || kGray_8_SkColorType == colorType) {
         return false;
     }
 
     // FIXME: Call virtual function when it lands.
     SkImageInfo info = SkImageInfo::Make(0, 0, colorType, fDecoder->getInfo().alphaType(),
             fDecoder->getInfo().profileType());
     return conversion_possible(info, fDecoder->getInfo());
 }