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    ///@name non-virtual helpers
55    void blitMaskRegion(const SkMask& mask, const SkRegion& clip);
56    void blitRectRegion(const SkIRect& rect, const SkRegion& clip);
57    void blitRegion(const SkRegion& clip);
58    ///@}
59
60    /** @name Factories
61        Return the correct blitter to use given the specified context.
62     */
63    static SkBlitter* Choose(const SkBitmap& device,
64                             const SkMatrix& matrix,
65                             const SkPaint& paint) {
66        return Choose(device, matrix, paint, NULL, 0);
67    }
68
69    static SkBlitter* Choose(const SkBitmap& device,
70                             const SkMatrix& matrix,
71                             const SkPaint& paint,
72                             void* storage, size_t storageSize);
73
74    static SkBlitter* ChooseSprite(const SkBitmap& device,
75                                   const SkPaint&,
76                                   const SkBitmap& src,
77                                   int left, int top,
78                                   void* storage, size_t storageSize);
79    ///@}
80
81private:
82};
83
84/** This blitter silently never draws anything.
85*/
86class SkNullBlitter : public SkBlitter {
87public:
88    virtual void blitH(int x, int y, int width) SK_OVERRIDE;
89    virtual void blitAntiH(int x, int y, const SkAlpha[],
90                           const int16_t runs[]) SK_OVERRIDE;
91    virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE;
92    virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE;
93    virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE;
94    virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE;
95};
96
97/** Wraps another (real) blitter, and ensures that the real blitter is only
98    called with coordinates that have been clipped by the specified clipRect.
99    This means the caller need not perform the clipping ahead of time.
100*/
101class SkRectClipBlitter : public SkBlitter {
102public:
103    void init(SkBlitter* blitter, const SkIRect& clipRect) {
104        SkASSERT(!clipRect.isEmpty());
105        fBlitter = blitter;
106        fClipRect = clipRect;
107    }
108
109    virtual void blitH(int x, int y, int width) SK_OVERRIDE;
110    virtual void blitAntiH(int x, int y, const SkAlpha[],
111                           const int16_t runs[]) SK_OVERRIDE;
112    virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE;
113    virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE;
114    virtual void blitAntiRect(int x, int y, int width, int height,
115                     SkAlpha leftAlpha, SkAlpha rightAlpha) SK_OVERRIDE;
116    virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE;
117    virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE;
118
119private:
120    SkBlitter*  fBlitter;
121    SkIRect     fClipRect;
122};
123
124/** Wraps another (real) blitter, and ensures that the real blitter is only
125    called with coordinates that have been clipped by the specified clipRgn.
126    This means the caller need not perform the clipping ahead of time.
127*/
128class SkRgnClipBlitter : public SkBlitter {
129public:
130    void init(SkBlitter* blitter, const SkRegion* clipRgn) {
131        SkASSERT(clipRgn && !clipRgn->isEmpty());
132        fBlitter = blitter;
133        fRgn = clipRgn;
134    }
135
136    virtual void blitH(int x, int y, int width) SK_OVERRIDE;
137    virtual void blitAntiH(int x, int y, const SkAlpha[],
138                           const int16_t runs[]) SK_OVERRIDE;
139    virtual void blitV(int x, int y, int height, SkAlpha alpha) SK_OVERRIDE;
140    virtual void blitRect(int x, int y, int width, int height) SK_OVERRIDE;
141    virtual void blitAntiRect(int x, int y, int width, int height,
142                     SkAlpha leftAlpha, SkAlpha rightAlpha) SK_OVERRIDE;
143    virtual void blitMask(const SkMask&, const SkIRect& clip) SK_OVERRIDE;
144    virtual const SkBitmap* justAnOpaqueColor(uint32_t* value) SK_OVERRIDE;
145
146private:
147    SkBlitter*      fBlitter;
148    const SkRegion* fRgn;
149};
150
151/** Factory to set up the appropriate most-efficient wrapper blitter
152    to apply a clip. Returns a pointer to a member, so lifetime must
153    be managed carefully.
154*/
155class SkBlitterClipper {
156public:
157    SkBlitter*  apply(SkBlitter* blitter, const SkRegion* clip,
158                      const SkIRect* bounds = NULL);
159
160private:
161    SkNullBlitter       fNullBlitter;
162    SkRectClipBlitter   fRectBlitter;
163    SkRgnClipBlitter    fRgnBlitter;
164};
165
166#endif
167