SkBlitter.h revision 84e922bfb3e7a03f6e35beb2f1e4f2657e7cd3e9 
1
2/*
3 * Copyright 2006 The Android Open Source Project
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
9
10#ifndef SkBlitter_DEFINED
11#define SkBlitter_DEFINED
12
13#include "SkBitmap.h"
14#include "SkMatrix.h"
15#include "SkPaint.h"
16#include "SkRefCnt.h"
17#include "SkRegion.h"
18#include "SkMask.h"
19
20/** SkBlitter and its subclasses are responsible for actually writing pixels
21    into memory. Besides efficiency, they handle clipping and antialiasing.
22*/
23class SkBlitter {
24public:
25    virtual ~SkBlitter();
26
27    /// Blit a horizontal run of one or more pixels.
28    virtual void blitH(int x, int y, int width);
29    /// Blit a horizontal run of antialiased pixels; runs[] is a *sparse*
30    /// zero-terminated run-length encoding of spans of constant alpha values.
31    virtual void blitAntiH(int x, int y, const SkAlpha antialias[],
32                           const int16_t runs[]);
33    /// Blit a vertical run of pixels with a constant alpha value.
34    virtual void blitV(int x, int y, int height, SkAlpha alpha);
35    /// Blit a solid rectangle one or more pixels wide.
36    virtual void blitRect(int x, int y, int width, int height);
37    /** Blit a rectangle with one alpha-blended column on the left,
38        width (zero or more) opaque pixels, and one alpha-blended column
39        on the right.
40        The result will always be at least two pixels wide.
41    */
42    virtual void blitAntiRect(int x, int y, int width, int height,
43                              SkAlpha leftAlpha, SkAlpha rightAlpha);
44    /// Blit a pattern of pixels defined by a rectangle-clipped mask;
45    /// typically used for text.
46    virtual void blitMask(const SkMask&, const SkIRect& clip);
47
48    /** If the blitter just sets a single value for each pixel, return the
49        bitmap it draws into, and assign value. If not, return NULL and ignore
50        the value parameter.
51    */
52    virtual const SkBitmap* justAnOpaqueColor(uint32_t* value);
53
54    /**
55     *  Special method just to identify the null blitter, which is returned
56     *  from Choose() if the request cannot be fulfilled. Default impl
57     *  returns false.
58     */
59    virtual bool isNullBlitter() const;
60
61    ///@name non-virtual helpers
62    void blitMaskRegion(const SkMask& mask, const SkRegion& clip);
63    void blitRectRegion(const SkIRect& rect, const SkRegion& clip);
64    void blitRegion(const SkRegion& clip);
65    ///@}
66
67    /** @name Factories
68        Return the correct blitter to use given the specified context.
69     */
70    static SkBlitter* Choose(const SkBitmap& device,
71                             const SkMatrix& matrix,
72                             const SkPaint& paint) {
73        return Choose(device, matrix, paint, NULL, 0);
74    }
75
76    static SkBlitter* Choose(const SkBitmap& device,
77                             const SkMatrix& matrix,
78                             const SkPaint& paint,
79                             void* storage, size_t storageSize);
80
81    static SkBlitter* ChooseSprite(const SkBitmap& device,
82                                   const SkPaint&,
83                                   const SkBitmap& src,
84                                   int left, int top,
85                                   void* storage, size_t storageSize);
86    ///@}
87
88private:
89};
90
91/** This blitter silently never draws anything.
92*/
93class SkNullBlitter : public SkBlitter {
94public:
95    virtual void blitH(int x, int y, int width) SK_OVERRIDE;
96    virtual void blitAntiH(int x, int y, const SkAlpha[],
97                           const int16_t runs[]) SK_OVERRIDE;
98    virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE;
99    virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE;
100    virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE;
101    virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE;
102    virtual bool isNullBlitter() const SK_OVERRIDE;
103};
104
105/** Wraps another (real) blitter, and ensures that the real blitter is only
106    called with coordinates that have been clipped by the specified clipRect.
107    This means the caller need not perform the clipping ahead of time.
108*/
109class SkRectClipBlitter : public SkBlitter {
110public:
111    void init(SkBlitter* blitter, const SkIRect& clipRect) {
112        SkASSERT(!clipRect.isEmpty());
113        fBlitter = blitter;
114        fClipRect = clipRect;
115    }
116
117    virtual void blitH(int x, int y, int width) SK_OVERRIDE;
118    virtual void blitAntiH(int x, int y, const SkAlpha[],
119                           const int16_t runs[]) SK_OVERRIDE;
120    virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE;
121    virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE;
122    virtual void blitAntiRect(int x, int y, int width, int height,
123                     SkAlpha leftAlpha, SkAlpha rightAlpha) SK_OVERRIDE;
124    virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE;
125    virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE;
126
127private:
128    SkBlitter*  fBlitter;
129    SkIRect     fClipRect;
130};
131
132/** Wraps another (real) blitter, and ensures that the real blitter is only
133    called with coordinates that have been clipped by the specified clipRgn.
134    This means the caller need not perform the clipping ahead of time.
135*/
136class SkRgnClipBlitter : public SkBlitter {
137public:
138    void init(SkBlitter* blitter, const SkRegion* clipRgn) {
139        SkASSERT(clipRgn && !clipRgn->isEmpty());
140        fBlitter = blitter;
141        fRgn = clipRgn;
142    }
143
144    virtual void blitH(int x, int y, int width) SK_OVERRIDE;
145    virtual void blitAntiH(int x, int y, const SkAlpha[],
146                           const int16_t runs[]) SK_OVERRIDE;
147    virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE;
148    virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE;
149    virtual void blitAntiRect(int x, int y, int width, int height,
150                     SkAlpha leftAlpha, SkAlpha rightAlpha) SK_OVERRIDE;
151    virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE;
152    virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE;
153
154private:
155    SkBlitter*      fBlitter;
156    const SkRegion* fRgn;
157};
158
159/** Factory to set up the appropriate most-efficient wrapper blitter
160    to apply a clip. Returns a pointer to a member, so lifetime must
161    be managed carefully.
162*/
163class SkBlitterClipper {
164public:
165    SkBlitter*  apply(SkBlitter* blitter, const SkRegion* clip,
166                      const SkIRect* bounds = NULL);
167
168private:
169    SkNullBlitter       fNullBlitter;
170    SkRectClipBlitter   fRectBlitter;
171    SkRgnClipBlitter    fRgnBlitter;
172};
173
174#endif
175