SkPorterDuff.h revision 048522dd2aa45d1b4bf52944527f877b30ea45fd 
1/*
2 * Copyright (C) 2006 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef SkPorterDuff_DEFINED
18#define SkPorterDuff_DEFINED
19
20#include "SkColor.h"
21#include "SkXfermode.h"
22
23class SkXfermode;
24
25/** DEPRECATED - use SkXfermode::Mode instead
26 */
27class SkPorterDuff {
28public:
29    /** List of predefined xfermodes. In general, the algebra for the modes
30        uses the following symbols:
31        Sa, Sc  - source alpha and color
32        Da, Dc - destination alpha and color (before compositing)
33        [a, c] - Resulting (alpha, color) values
34        For these equations, the colors are in premultiplied state.
35        If no xfermode is specified, kSrcOver is assumed.
36    */
37    enum Mode {
38        kClear_Mode,    //!< [0, 0]
39        kSrc_Mode,      //!< [Sa, Sc]
40        kDst_Mode,      //!< [Da, Dc]
41        kSrcOver_Mode,  //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc]
42        kDstOver_Mode,  //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc]
43        kSrcIn_Mode,    //!< [Sa * Da, Sc * Da]
44        kDstIn_Mode,    //!< [Sa * Da, Sa * Dc]
45        kSrcOut_Mode,   //!< [Sa * (1 - Da), Sc * (1 - Da)]
46        kDstOut_Mode,   //!< [Da * (1 - Sa), Dc * (1 - Sa)]
47        kSrcATop_Mode,  //!< [Da, Sc * Da + (1 - Sa) * Dc]
48        kDstATop_Mode,  //!< [Sa, Sa * Dc + Sc * (1 - Da)]
49        kXor_Mode,      //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc]
50        kDarken_Mode,   //!< [Sa + Da - Sa*Da, Sc*(1 - Da) + Dc*(1 - Sa) + min(Sc, Dc)]
51        kLighten_Mode,  //!< [Sa + Da - Sa*Da, Sc*(1 - Da) + Dc*(1 - Sa) + max(Sc, Dc)]
52        kMultiply_Mode, //!< [Sa * Da, Sc * Dc]
53        kScreen_Mode,   //!< [Sa + Da - Sa * Da, Sc + Dc - Sc * Dc]
54        kAdd_Mode,      //!< Saturate(S + D)
55
56        kModeCount
57    };
58
59    /** Return an SkXfermode object for the specified mode.
60    */
61    static SkXfermode* CreateXfermode(Mode mode);
62
63    /** Return a function pointer to a routine that applies the specified
64        porter-duff transfer mode.
65    */
66    static SkXfermodeProc GetXfermodeProc(Mode mode);
67
68    /** Return a function pointer to a routine that applies the specified
69        porter-duff transfer mode and srcColor to a 16bit device color. Note,
70        if the mode+srcColor might return a non-opaque color, then there is not
71        16bit proc, and this will return NULL.
72    */
73    static SkXfermodeProc16 GetXfermodeProc16(Mode mode, SkColor srcColor);
74
75    /** If the specified xfermode advertises itself as one of the porterduff
76        modes (via SkXfermode::Coeff), return true and if not null, set mode
77        to the corresponding porterduff mode. If it is not recognized as a one,
78        return false and ignore the mode parameter.
79    */
80    static bool IsMode(SkXfermode*, Mode* mode);
81
82    /** Return the corersponding SkXfermode::Mode
83     */
84    static SkXfermode::Mode ToXfermodeMode(Mode);
85};
86
87#endif
88
89