Adding png scanline decoding to kIndex8

include/codec/SkCodec.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCodec_DEFINED
 #define SkCodec_DEFINED
 
@@ skipping 52 matching lines @@
      *  This object is owned by the SkCodec, which will handle its lifetime. The
      *  returned object is only valid until the SkCodec is deleted or the next
      *  call to getScanlineDecoder, whichever comes first.
      *
      *  Calling a second time will rewind and replace the existing one with a
      *  new one. If the stream cannot be rewound, this will delete the existing
      *  one and return NULL.
      *
      *  @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
      *  SkStream.
      *
      *  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);
 
     /**
      *  Some images may initially report that they have alpha due to the format
      *  of the encoded data, but then never use any colors which have alpha
      *  less than 100%. This function can be called *after* decoding to
      *  determine if such an image truly had alpha. Calling it before decoding
      *  is undefined.
      *  FIXME: see skbug.com/3582.
      */
@@ skipping 28 matching lines @@
     virtual SkEncodedFormat onGetEncodedFormat() const = 0;
 
     /**
      *  Override if your codec supports scanline decoding.
      *
      *  As in onGetPixels(), the implementation must call rewindIfNeeded() and
      *  handle as appropriate.
      *
      *  @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;
     }
 
     virtual bool onReallyHasAlpha() const { return false; }
 
     enum RewindState {
         kRewound_RewindState,
         kNoRewindNecessary_RewindState,
         kCouldNotRewind_RewindState
     };
@@ skipping 26 matching lines @@
 #ifdef SK_SUPPORT_LEGACY_BOOL_ONGETINFO
     const SkImageInfo                   fInfo;
 #endif  //  SK_SUPPORT_LEGACY_BOOL_ONGETINFO
     SkAutoTDelete<SkStream>             fStream;
     bool                                fNeedsRewind;
     SkAutoTDelete<SkScanlineDecoder>    fScanlineDecoder;
 
     typedef SkImageGenerator INHERITED;
 };
 #endif // SkCodec_DEFINED