Adding png scanline decoding to kIndex8

include/codec/SkCodec.h

Index: include/codec/SkCodec.h
diff --git a/include/codec/SkCodec.h b/include/codec/SkCodec.h
index 6f313a1c7058715c8e7c95a82ca1448b152b245e..b3898892b09c3ce3fcaec86b2f9d87465f61cff3 100644
--- a/include/codec/SkCodec.h
+++ b/include/codec/SkCodec.h
@@ -70,6 +70,15 @@ public:
      *
      *  @param dstInfo Info of the destination. If the dimensions do not match
      *      those of getInfo, this implies a scale.
+     *  @param options Contains decoding options, including if memory is zero
+     *      initialized.
+     *  @param ctable A pointer to a color table.  When dstInfo.colorType() is
+     *      kIndex8, this should be non-NULL and have enough storage for 256
+     *      colors.  The color table will be populated after decoding the palette.
+     *  @param ctableCount A pointer to the size of the color table.  When
+     *      dstInfo.colorType() is kIndex8, this should be non-NULL.  It will
+     *      be modified to the true size of the color table (<= 256) after
+     *      decoding the palette.
      *  @return New SkScanlineDecoder, or NULL on failure.
      *
      *  NOTE: If any rows were previously decoded, this requires rewinding the
@@ -78,6 +87,13 @@ public:
      *  NOTE: The scanline decoder is owned by the SkCodec and will delete it
      *  when the SkCodec is deleted.
      */
+    SkScanlineDecoder* getScanlineDecoder(const SkImageInfo& dstInfo, const Options* options,

[djsollen, 2015/04/29 14:02:58]

const* for options here and const& on the protected version. Seems like we
should stick with one.

[scroggo, 2015/04/29 14:13:22]

This follows a pattern I've used elsewhere in SkCodec/SkImageGenerator, and I
believe I've seen it elsewhere.

It is deliberate - Options is optional, so we make the public version a pointer,
allowing a client to pass NULL. Rather than making the protected version also
optional, resulting in each implementation checking for NULL, and potentially
deciding differently what the default should be, the implementation for the
public version passes a default version if the client passed NULL.

+                                          SkPMColor ctable[], int* ctableCount);
+
+    /**
+     *  Simplified version of getScanlineDecoder() that asserts that info is NOT
+     *  kIndex8_SkColorType and uses the default Options.
+     */
     SkScanlineDecoder* getScanlineDecoder(const SkImageInfo& dstInfo);
 
     /**
@@ -126,10 +142,22 @@ protected:
      *
      *  @param dstInfo Info of the destination. If the dimensions do not match
      *      those of getInfo, this implies a scale.
+     *  @param options Contains decoding options, including if memory is zero
+     *      initialized.
+     *  @param ctable A pointer to a color table.  When dstInfo.colorType() is
+     *      kIndex8, this should be non-NULL and have enough storage for 256
+     *      colors.  The color table will be populated after decoding the palette.
+     *  @param ctableCount A pointer to the size of the color table.  When
+     *      dstInfo.colorType() is kIndex8, this should be non-NULL.  It will
+     *      be modified to the true size of the color table (<= 256) after
+     *      decoding the palette.
      *  @return New SkScanlineDecoder on success, NULL otherwise. The SkCodec
      *      will take ownership of the returned scanline decoder.
      */
-    virtual SkScanlineDecoder* onGetScanlineDecoder(const SkImageInfo& dstInfo) {
+    virtual SkScanlineDecoder* onGetScanlineDecoder(const SkImageInfo& dstInfo,
+                                                    const Options& options,
+                                                    SkPMColor ctable[],
+                                                    int* ctableCount) {
         return NULL;
     }