src/codec/SkBmpRLECodec.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.
 */

#include "SkBmpCodec.h"
#include "SkColorTable.h"
#include "SkImageInfo.h"
#include "SkTypes.h"

/*
 * This class implements the decoding for bmp images that use an RLE encoding
 */
class SkBmpRLECodec : public SkBmpCodec {
public:

    /*
     * Creates an instance of the decoder
     *
     * Called only by SkBmpCodec::NewFromStream
     * There should be no other callers despite this being public
     *
     * @param srcInfo contains the source width and height
     * @param stream the stream of encoded image data
     * @param bitsPerPixel the number of bits used to store each pixel
     * @param numColors the number of colors in the color table
     * @param bytesPerColor the number of bytes in the stream used to represent
                            each color in the color table
     * @param offset the offset of the image pixel data from the end of the
     *               headers
     * @param rowOrder indicates whether rows are ordered top-down or bottom-up
     * @param RLEBytes indicates the amount of data left in the stream
     *                 after decoding the headers
     */
    SkBmpRLECodec(const SkImageInfo& srcInfo, SkStream* stream,
                  uint16_t bitsPerPixel, uint32_t numColors,
                  uint32_t bytesPerColor, uint32_t offset,
                  SkBmpCodec::RowOrder rowOrder, size_t RLEBytes);

protected:

    Result onGetPixels(const SkImageInfo& dstInfo, void* dst,
                       size_t dstRowBytes, const Options&, SkPMColor*,
                       int*) override;

private:

    /*
     * Creates the color table
     * Sets colorCount to the new color count if it is non-nullptr
     */
    bool createColorTable(int* colorCount);

    bool initializeStreamBuffer();

    /*
     * Before signalling kIncompleteInput, we should attempt to load the
     * stream buffer with additional data.
     *
     * @return the number of bytes remaining in the stream buffer after
     *         attempting to read more bytes from the stream
     */
    size_t checkForMoreData();

    /*
     * Set an RLE pixel using the color table
     */
    void setPixel(void* dst, size_t dstRowBytes,
                  const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
                  uint8_t index);
    /*
     * Set an RLE24 pixel from R, G, B values
     */
    void setRGBPixel(void* dst, size_t dstRowBytes,
                     const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
                     uint8_t red, uint8_t green, uint8_t blue);

    /*
     * Performs the bitmap decoding for RLE input format
     */
    Result decode(const SkImageInfo& dstInfo, void* dst,
                  size_t dstRowBytes, const Options& opts);

    SkAutoTUnref<SkColorTable>          fColorTable;    // owned
    const uint32_t                      fNumColors;
    const uint32_t                      fBytesPerColor;
    const uint32_t                      fOffset;
    SkAutoTDeleteArray<uint8_t>         fStreamBuffer;
    size_t                              fRLEBytes;
    uint32_t                            fCurrRLEByte;

    typedef SkBmpCodec INHERITED;
};