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