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 "SkBmpCodec.h" 11 #include "SkColorTable.h" 12 #include "SkImageInfo.h" 13 #include "SkSampler.h" 14 #include "SkTypes.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(int width, int height, const 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 protected: 45 46 Result onGetPixels(const SkImageInfo& dstInfo, void* dst, 47 size_t dstRowBytes, const Options&, 48 int*) override; 49 50 SkCodec::Result onPrepareToDecode(const SkImageInfo& dstInfo, 51 const SkCodec::Options& options) override; 52 53 private: 54 55 /* 56 * Creates the color table 57 * Sets colorCount to the new color count if it is non-nullptr 58 */ 59 bool createColorTable(SkColorType dstColorType); 60 61 bool initializeStreamBuffer(); 62 63 /* 64 * Before signalling kIncompleteInput, we should attempt to load the 65 * stream buffer with additional data. 66 * 67 * @return the number of bytes remaining in the stream buffer after 68 * attempting to read more bytes from the stream 69 */ 70 size_t checkForMoreData(); 71 72 /* 73 * Set an RLE pixel using the color table 74 */ 75 void setPixel(void* dst, size_t dstRowBytes, 76 const SkImageInfo& dstInfo, uint32_t x, uint32_t y, 77 uint8_t index); 78 /* 79 * Set an RLE24 pixel from R, G, B values 80 */ 81 void setRGBPixel(void* dst, size_t dstRowBytes, 82 const SkImageInfo& dstInfo, uint32_t x, uint32_t y, 83 uint8_t red, uint8_t green, uint8_t blue); 84 85 /* 86 * If dst is NULL, this is a signal to skip the rows. 87 */ 88 int decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, 89 const Options& opts) override; 90 int decodeRLE(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes); 91 92 bool skipRows(int count) override; 93 94 SkSampler* getSampler(bool createIfNecessary) override; 95 96 sk_sp<SkColorTable> fColorTable; 97 // fNumColors is the number specified in the header, or 0 if not present in the header. 98 const uint32_t fNumColors; 99 const uint32_t fBytesPerColor; 100 const uint32_t fOffset; 101 102 static constexpr size_t kBufferSize = 4096; 103 uint8_t fStreamBuffer[kBufferSize]; 104 size_t fBytesBuffered; 105 106 uint32_t fCurrRLEByte; 107 int fSampleX; 108 std::unique_ptr<SkSampler> fSampler; 109 110 // Scanline decodes allow the client to ask for a single scanline at a time. 111 // This can be tricky when the RLE encoding instructs the decoder to jump down 112 // multiple lines. This field keeps track of lines that need to be skipped 113 // on subsequent calls to decodeRows(). 114 int fLinesToSkip; 115 116 typedef SkBmpCodec INHERITED; 117 }; 118 #endif // SkBmpRLECodec_DEFINED 119