Add SkAndroidCodec::computeSampledSize

Bug: b/63909536

Android's ImageDecoder API takes as input an arbitrary width and height
to scale the image to. Internally, this uses SkAndroidCodec to sample,
and then (if not a perfect match) scales to the desired size with
drawing.

computeSampledSize is a modified version of what ImageDecoder currently
does to convert from arbitrary dimensions to a sampleSize. Moving it
here allows it to be shared by SkAnimatedImage. The modified version
also corrects two bugs:
- a client using the dimensions returned by getSampledDimensions
  previously may have resulted in ImageDecoder decoding to a larger
  size and then scaling it. (example found in tests: dog.jpg is
  180 x 180. getSampledDimensions(8) returns 23 x 23, but the old
  method resulted in using sampleSize of 7 and downscaling the resulting
  25 x 25 image.)
- recompute the sampleSize based on the size returned by
  getSampledDimensions.

Change-Id: I022040e8bac31c20988903a0452257f7ae902bc7
Reviewed-on: https://skia-review.googlesource.com/94620
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/codec/SkAndroidCodec.h b/include/codec/SkAndroidCodec.h
index 2bf38025bf..0746f066c8 100644
--- a/include/codec/SkAndroidCodec.h
+++ b/include/codec/SkAndroidCodec.h
@@ -91,6 +91,17 @@ public:
                                                 sk_sp<SkColorSpace> prefColorSpace = nullptr);
 
     /**
+     *  Compute the appropriate sample size to get to |size|.
+     *
+     *  @param size As an input parameter, the desired output size of
+     *      the decode. As an output parameter, the smallest sampled size
+     *      larger than the input.
+     *  @return the sample size to set AndroidOptions::fSampleSize to decode
+     *      to the output |size|.
+     */
+    int computeSampleSize(SkISize* size) const;
+
+    /**
      *  Returns the dimensions of the scaled output image, for an input
      *  sampleSize.
      *