Prototype of RAW decoding in Skia.

src/codec/SkRawCodec.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 SkRawCodec_DEFINED
+#define SkRawCodec_DEFINED
+
+#include "SkCodec.h"
+#include "SkImageInfo.h"
+#include "SkStream.h"
+
+#include "dng_host.h"
+
+/*
+ *
+ * This class implements the decoding for jpeg images
+ *
+ */
+class SkRawCodec : public SkCodec {
+public:
+
+    /*
+     * Checks the start of the stream to see if the image is a RAW
+     * Does not take ownership of the stream
+     */
+    static bool IsRaw(SkStream*);
+
+    /*
+     * Assumes IsRaw was called and returned true
+     * Creates a RAW decoder
+     * Takes ownership of the stream
+     */
+    static SkCodec* NewFromStream(SkStream*);
+
+protected:
+
+    /*
+     * Initiates the RAW decode
+     */
+    Result onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, const Options&,
+            SkPMColor*, int*, int*) override;
+
+    SkEncodedFormat onGetEncodedFormat() const override {
+        return kRAW_SkEncodedFormat;
+    }
+
+private:
+
+    /*
+     * Creates an instance of the decoder
+     * Called only by NewFromStream
+     *
+     * @param srcInfo contains the source width and height
+     * @param stream the encoded image data
+     */
+    SkRawCodec(const SkImageInfo& srcInfo, SkStream* stream);
+
+    // scanline decoding
+    /*void initializeSwizzler(const SkImageInfo& dstInfo, const Options& options);

[msarett, 2015/12/18 16:26:13]

I think these methods are unnecessary given that you have mentioned in the past
that RAW is not conducive to scanline decoding?

Scanline decoding + SkSampledCodec is one way that we implement scaling for
other codecs, but that does not mean RAW needs to be implemented this way (and
it looks like it won't be).

If SkRawCodec/SkRawAdapterCodec intend to provide scaling, they can use their
own solution.  For example, SkWebpCodec/SkWebpAdapterCodec use libwebp to
provide scaling.

[yujieqin, 2016/01/06 18:47:19]

Removed.

+    SkSampler* getSampler(bool createIfNecessary) override;
+    Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
+            SkPMColor ctable[], int* ctableCount) override;
+    int onGetScanlines(void* dst, int count, size_t rowBytes) override;
+    bool onSkipScanlines(int count) override;*/
+
+    typedef SkCodec INHERITED;
+};
+
+#endif