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 */
19class SkBmpRLECodec : public SkBmpCodec {
20public:
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
46protected:
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
55private:
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