skia2/include/core/SkPngChunkReader.h
scroggo cf98fa9311 Add SkPngChunkReader.
This class allows a client of SkCodec to read chunks in the data
stream that are not recognized by libpng. This is used by Android
to specify ninepatch data.

Taken from SkImageDecoder::Peeker. Modify the name of the class
and its method to be more specific to their use. Make
SkImageDecoder::Peeker a subclass of the new class, to help stage
the change in Android.

Add a test to verify that it works.

BUG=skia:4574
BUG=skia:3257

Committed: https://skia.googlesource.com/skia/+/3389e00136188800b98ca69488c0418c374fd78b

Review URL: https://codereview.chromium.org/1040453002
2015-11-23 08:14:40 -08:00

46 lines
1.5 KiB
C++

/*
* 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 SkPngChunkReader_DEFINED
#define SkPngChunkReader_DEFINED
#include "SkTypes.h"
#include "SkRefCnt.h"
/**
* SkPngChunkReader
*
* Base class for optional callbacks to retrieve meta/chunk data out of a PNG
* encoded image as it is being decoded.
* Used by SkImageDecoder and SkCodec.
*/
class SkPngChunkReader : public SkRefCnt {
public:
/**
* This will be called by the decoder when it sees an unknown chunk.
*
* Use by SkCodec:
* Depending on the location of the unknown chunks, this callback may be
* called by
* - the factory (NewFromStream/NewFromData)
* - getPixels
* - startScanlineDecode
* - the first call to getScanlines/skipScanlines
* The callback may be called from a different thread (e.g. if the SkCodec
* is passed to another thread), and it may be called multiple times, if
* the SkCodec is used multiple times.
*
* @param tag Name for this type of chunk.
* @param data Data to be interpreted by the subclass.
* @param length Number of bytes of data in the chunk.
* @return true to continue decoding, or false to indicate an error, which
* will cause the decoder to not return the image.
*/
virtual bool readChunk(const char tag[], const void* data, size_t length) = 0;
};
#endif // SkPngChunkReader_DEFINED