SkScaledBitmapSampler.h revision dac4a1d518a4788c3e2475d68cbe8683b4a448ff 
1
2/*
3 * Copyright 2011 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8#ifndef SkScaledBitmapSampler_DEFINED
9#define SkScaledBitmapSampler_DEFINED
10
11#include "SkTypes.h"
12#include "SkColor.h"
13#include "SkImageDecoder.h"
14
15class SkBitmap;
16
17class SkScaledBitmapSampler {
18public:
19    SkScaledBitmapSampler(int origWidth, int origHeight, int cellSize);
20
21    int scaledWidth() const { return fScaledWidth; }
22    int scaledHeight() const { return fScaledHeight; }
23
24    int srcY0() const { return fY0; }
25    int srcDX() const { return fDX; }
26    int srcDY() const { return fDY; }
27
28    enum SrcConfig {
29        kGray,  // 1 byte per pixel
30        kIndex, // 1 byte per pixel
31        kRGB,   // 3 bytes per pixel
32        kRGBX,  // 4 byes per pixel (ignore 4th)
33        kRGBA,  // 4 bytes per pixel
34        kRGB_565 // 2 bytes per pixel
35    };
36
37    // Given a dst bitmap (with pixels already allocated) and a src-config,
38    // prepares iterator to process the src colors and write them into dst.
39    // Returns false if the request cannot be fulfulled.
40    bool begin(SkBitmap* dst, SrcConfig sc, const SkImageDecoder& decoder,
41               const SkPMColor* = NULL);
42    // call with row of src pixels, for y = 0...scaledHeight-1.
43    // returns true if the row had non-opaque alpha in it
44    bool next(const uint8_t* SK_RESTRICT src);
45
46    // Like next(), but specifies the y value of the source row, so the
47    // rows can come in any order. If the row is not part of the output
48    // sample, it will be skipped. Only sampleInterlaced OR next should
49    // be called for one SkScaledBitmapSampler.
50    bool sampleInterlaced(const uint8_t* SK_RESTRICT src, int srcY);
51
52    typedef bool (*RowProc)(void* SK_RESTRICT dstRow,
53                            const uint8_t* SK_RESTRICT src,
54                            int width, int deltaSrc, int y,
55                            const SkPMColor[]);
56
57private:
58    int fScaledWidth;
59    int fScaledHeight;
60
61    int fX0;    // first X coord to sample
62    int fY0;    // first Y coord (scanline) to sample
63    int fDX;    // step between X samples
64    int fDY;    // step between Y samples
65
66#ifdef SK_DEBUG
67    // Keep track of whether the caller is using next or sampleInterlaced.
68    // Only one can be used per sampler.
69    enum SampleMode {
70        kUninitialized_SampleMode,
71        kConsecutive_SampleMode,
72        kInterlaced_SampleMode,
73    };
74
75    SampleMode fSampleMode;
76#endif
77
78    // setup state
79    char*   fDstRow; // points into bitmap's pixels
80    size_t  fDstRowBytes;
81    int     fCurrY; // used for dithering
82    int     fSrcPixelSize;  // 1, 3, 4
83    RowProc fRowProc;
84
85    // optional reference to the src colors if the src is a palette model
86    const SkPMColor* fCTable;
87
88#ifdef SK_DEBUG
89    // Helper class allowing a test to have access to fRowProc.
90    friend class RowProcTester;
91#endif
92};
93
94#endif
95