SkScaledCodec class

include/codec/SkCodec.h

Index: include/codec/SkCodec.h
diff --git a/include/codec/SkCodec.h b/include/codec/SkCodec.h
index 1cdc88d4adcfc0dc4e028913348dd21c287e50e7..f20298e5891b84983f86f805ff47608fee668a7d 100644
--- a/include/codec/SkCodec.h
+++ b/include/codec/SkCodec.h
@@ -52,11 +52,25 @@ public:
      *  Return a size that approximately supports the desired scale factor.
      *  The codec may not be able to scale efficiently to the exact scale
      *  factor requested, so return a size that approximates that scale.
+     *  The returned value is the codec's suggestion for the closest valid
+     *  scale that it can natively support
      */
     SkISize getScaledDimensions(float desiredScale) const {
         return this->onGetScaledDimensions(desiredScale);
     }
 
+    /*
+     * Checks if we can patially natively scale to the desiredScale, and partially natively scales

[scroggo, 2015/08/04 20:05:21]

"partially" is missing r (the first time)

[emmaleer, 2015/08/05 14:47:51]

Acknowledged.

+     * the dimensions if possible.
+     * Returns the new sampleSize, which is used to finish scaling to the desiredScale.
+     * Ex: desiredScale = 1/6. Natively can scale by 1/2. New sampleSize = 3, as there is still
+     * 1/3 scaling left to do, which is done by sampling.
+     * Returns -1 if partial native scaling is not supported.
+     */
+    int partiallyNativelyScale(float desiredScale) {

[scroggo, 2015/08/04 20:05:21]

I'm not a huge fan of this name. I am not sure I have a better name though. This
does the following:

A) Tells the codec to scale
B) Returns the sample size needed afterwards

On a related note, this function behaves a lot differently from the other
functions. Although I've been arguing recently that SkCodec is not really
stateless, the only state it currently has is related to the stream - no other
APIs should change future function calls.

This function also feels like it leaks a lot of SkScaledCodec into SkCodec and
SkJpegCodec.

Right now I'm leaning towards removing the partial scaling, with a TODO and a
bug to do it later.

[emmaleer, 2015/08/05 14:47:51]

Okay, I'll first upload the changes for future reference, then remove partial
scaling. 

+        return this->onPartiallyNativelyScale(desiredScale);
+    }
+
     /**
      *  Return (via desiredSubset) a subset which can decoded from this codec,
      *  or false if this codec cannot decode subsets or anything similar to
@@ -252,6 +266,9 @@ protected:
         return this->getInfo().dimensions();
     }
 
+    virtual int onPartiallyNativelyScale(float desiredScale) {
+        return -1;
+    }
     virtual SkEncodedFormat onGetEncodedFormat() const = 0;
 
     virtual Result onGetPixels(const SkImageInfo& info,