1 /* 2 * Copyright 2015 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 #ifndef SkBmpRLECodec_DEFINED 8 #define SkBmpRLECodec_DEFINED 9 10 #include "include/core/SkImageInfo.h" 11 #include "include/core/SkTypes.h" 12 #include "src/codec/SkBmpCodec.h" 13 #include "src/codec/SkColorTable.h" 14 #include "src/codec/SkSampler.h" 15 16 /* 17 * This class implements the decoding for bmp images that use an RLE encoding 18 */ 19 class SkBmpRLECodec : public SkBmpCodec { 20 public: 21 22 /* 23 * Creates an instance of the decoder 24 * 25 * Called only by SkBmpCodec::MakeFromStream 26 * There should be no other callers despite this being public 27 * 28 * @param info contains properties of the encoded data 29 * @param stream the stream of encoded image data 30 * @param bitsPerPixel the number of bits used to store each pixel 31 * @param numColors the number of colors in the color table 32 * @param bytesPerColor the number of bytes in the stream used to represent 33 each color in the color table 34 * @param offset the offset of the image pixel data from the end of the 35 * headers 36 * @param rowOrder indicates whether rows are ordered top-down or bottom-up 37 */ 38 SkBmpRLECodec(SkEncodedInfo&& info, std::unique_ptr<SkStream>, 39 uint16_t bitsPerPixel, uint32_t numColors, uint32_t bytesPerColor, 40 uint32_t offset, SkCodec::SkScanlineOrder rowOrder); 41 42 int setSampleX(int); 43 44 int fillWidth() const; 45 46 protected: 47 48 Result onGetPixels(const SkImageInfo& dstInfo, void* dst, 49 size_t dstRowBytes, const Options&, 50 int*) override; 51 52 SkCodec::Result onPrepareToDecode(const SkImageInfo& dstInfo, 53 const SkCodec::Options& options) override; 54 55 private: 56 57 /* 58 * Creates the color table 59 * Sets colorCount to the new color count if it is non-nullptr 60 */ 61 bool createColorTable(SkColorType dstColorType); 62 63 bool initializeStreamBuffer(); 64 65 /* 66 * Before signalling kIncompleteInput, we should attempt to load the 67 * stream buffer with additional data. 68 * 69 * @return the number of bytes remaining in the stream buffer after 70 * attempting to read more bytes from the stream 71 */ 72 size_t checkForMoreData(); 73 74 /* 75 * Set an RLE pixel using the color table 76 */ 77 void setPixel(void* dst, size_t dstRowBytes, 78 const SkImageInfo& dstInfo, uint32_t x, uint32_t y, 79 uint8_t index); 80 /* 81 * Set an RLE24 pixel from R, G, B values 82 */ 83 void setRGBPixel(void* dst, size_t dstRowBytes, 84 const SkImageInfo& dstInfo, uint32_t x, uint32_t y, 85 uint8_t red, uint8_t green, uint8_t blue); 86 87 /* 88 * If dst is NULL, this is a signal to skip the rows. 89 */ 90 int decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, 91 const Options& opts) override; 92 int decodeRLE(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes); 93 94 bool skipRows(int count) override; 95 96 SkSampler* getSampler(bool createIfNecessary) override; 97 98 sk_sp<SkColorTable> fColorTable; 99 // fNumColors is the number specified in the header, or 0 if not present in the header. 100 const uint32_t fNumColors; 101 const uint32_t fBytesPerColor; 102 const uint32_t fOffset; 103 104 static constexpr size_t kBufferSize = 4096; 105 uint8_t fStreamBuffer[kBufferSize]; 106 size_t fBytesBuffered; 107 108 uint32_t fCurrRLEByte; 109 int fSampleX; 110 std::unique_ptr<SkSampler> fSampler; 111 112 // Scanline decodes allow the client to ask for a single scanline at a time. 113 // This can be tricky when the RLE encoding instructs the decoder to jump down 114 // multiple lines. This field keeps track of lines that need to be skipped 115 // on subsequent calls to decodeRows(). 116 int fLinesToSkip; 117 118 typedef SkBmpCodec INHERITED; 119 }; 120 #endif // SkBmpRLECodec_DEFINED 121