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 * @param RLEBytes indicates the amount of data left in the stream 36 * after decoding the headers 37 */ 38 SkBmpRLECodec(const SkImageInfo& srcInfo, SkStream* stream, 39 uint16_t bitsPerPixel, uint32_t numColors, uint32_t bytesPerColor, 40 uint32_t offset, SkCodec::SkScanlineOrder rowOrder, 41 size_t RLEBytes); 42 43 int setSampleX(int); 44 45 protected: 46 47 Result onGetPixels(const SkImageInfo& dstInfo, void* dst, 48 size_t dstRowBytes, const Options&, SkPMColor*, 49 int*, int*) override; 50 51 SkCodec::Result prepareToDecode(const SkImageInfo& dstInfo, 52 const SkCodec::Options& options, SkPMColor inputColorPtr[], 53 int* inputColorCount) 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(int* colorCount); 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 93 bool skipRows(int count) override; 94 95 SkSampler* getSampler(bool createIfNecessary) override; 96 97 SkAutoTUnref<SkColorTable> fColorTable; // owned 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 SkAutoTDeleteArray<uint8_t> fStreamBuffer; 103 size_t fRLEBytes; 104 const size_t fOrigRLEBytes; 105 uint32_t fCurrRLEByte; 106 int fSampleX; 107 SkAutoTDelete<SkSampler> fSampler; 108 109 // Scanline decodes allow the client to ask for a single scanline at a time. 110 // This can be tricky when the RLE encoding instructs the decoder to jump down 111 // multiple lines. This field keeps track of lines that need to be skipped 112 // on subsequent calls to decodeRows(). 113 int fLinesToSkip; 114 115 typedef SkBmpCodec INHERITED; 116 }; 117