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::NewFromStream 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, SkStream* stream, 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&, SkPMColor*, 48 int*, int*) override; 49 50 SkCodec::Result onPrepareToDecode(const SkImageInfo& dstInfo, 51 const SkCodec::Options& options, SkPMColor inputColorPtr[], 52 int* inputColorCount) override; 53 54 private: 55 56 /* 57 * Creates the color table 58 * Sets colorCount to the new color count if it is non-nullptr 59 */ 60 bool createColorTable(SkColorType dstColorType, int* colorCount); 61 62 bool initializeStreamBuffer(); 63 64 /* 65 * Before signalling kIncompleteInput, we should attempt to load the 66 * stream buffer with additional data. 67 * 68 * @return the number of bytes remaining in the stream buffer after 69 * attempting to read more bytes from the stream 70 */ 71 size_t checkForMoreData(); 72 73 /* 74 * Set an RLE pixel using the color table 75 */ 76 void setPixel(void* dst, size_t dstRowBytes, 77 const SkImageInfo& dstInfo, uint32_t x, uint32_t y, 78 uint8_t index); 79 /* 80 * Set an RLE24 pixel from R, G, B values 81 */ 82 void setRGBPixel(void* dst, size_t dstRowBytes, 83 const SkImageInfo& dstInfo, uint32_t x, uint32_t y, 84 uint8_t red, uint8_t green, uint8_t blue); 85 86 /* 87 * If dst is NULL, this is a signal to skip the rows. 88 */ 89 int decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes, 90 const Options& opts) override; 91 int decodeRLE(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes); 92 93 bool skipRows(int count) override; 94 95 SkSampler* getSampler(bool createIfNecessary) override; 96 97 sk_sp<SkColorTable> fColorTable; 98 // fNumColors is the number specified in the header, or 0 if not present in the header. 99 const uint32_t fNumColors; 100 const uint32_t fBytesPerColor; 101 const uint32_t fOffset; 102 103 static constexpr size_t kBufferSize = 4096; 104 uint8_t fStreamBuffer[kBufferSize]; 105 size_t fBytesBuffered; 106 107 uint32_t fCurrRLEByte; 108 int fSampleX; 109 std::unique_ptr<SkSampler> fSampler; 110 111 // Scanline decodes allow the client to ask for a single scanline at a time. 112 // This can be tricky when the RLE encoding instructs the decoder to jump down 113 // multiple lines. This field keeps track of lines that need to be skipped 114 // on subsequent calls to decodeRows(). 115 int fLinesToSkip; 116 117 typedef SkBmpCodec INHERITED; 118 }; 119 #endif // SkBmpRLECodec_DEFINED 120
