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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef SkPorterDuff_DEFINED
#define SkPorterDuff_DEFINED
#include "SkColor.h"
class SkXfermode;
class SkPorterDuff {
public:
/** List of predefined xfermodes. In general, the algebra for the modes
uses the following symbols:
Sa, Sc - source alpha and color
Da, Dc - destination alpha and color (before compositing)
[a, c] - Resulting (alpha, color) values
For these equations, the colors are in premultiplied state.
If no xfermode is specified, kSrcOver is assumed.
*/
enum Mode {
kClear_Mode, //!< [0, 0]
kSrc_Mode, //!< [Sa, Sc]
kDst_Mode, //!< [Da, Dc]
kSrcOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc]
kDstOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc]
kSrcIn_Mode, //!< [Sa * Da, Sc * Da]
kDstIn_Mode, //!< [Sa * Da, Sa * Dc]
kSrcOut_Mode, //!< [Sa * (1 - Da), Sc * (1 - Da)]
kDstOut_Mode, //!< [Da * (1 - Sa), Dc * (1 - Sa)]
kSrcATop_Mode, //!< [Da, Sc * Da + (1 - Sa) * Dc]
kDstATop_Mode, //!< [Sa, Sa * Dc + Sc * (1 - Da)]
kXor_Mode, //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc]
kDarken_Mode, //!< [Sa + Da - Sa*Da, Sc*(1 - Da) + Dc*(1 - Sa) + min(Sc, Dc)]
kLighten_Mode, //!< [Sa + Da - Sa*Da, Sc*(1 - Da) + Dc*(1 - Sa) + max(Sc, Dc)]
kMultiply_Mode, //!< [Sa * Da, Sc * Dc]
kScreen_Mode, //!< [Sa + Da - Sa * Da, Sc + Dc - Sc * Dc]
kModeCount
};
/** Return an SkXfermode object for the specified mode.
*/
static SkXfermode* CreateXfermode(Mode mode);
/** Return a function pointer to a routine that applies the specified
porter-duff transfer mode.
*/
static SkXfermodeProc GetXfermodeProc(Mode mode);
/** Return a function pointer to a routine that applies the specified
porter-duff transfer mode and srcColor to a 16bit device color. Note,
if the mode+srcColor might return a non-opaque color, then there is not
16bit proc, and this will return NULL.
*/
static SkXfermodeProc16 GetXfermodeProc16(Mode mode, SkColor srcColor);
/** If the specified xfermode advertises itself as one of the porterduff
modes (via SkXfermode::Coeff), return true and if not null, set mode
to the corresponding porterduff mode. If it is not recognized as a one,
return false and ignore the mode parameter.
*/
static bool IsMode(SkXfermode*, Mode* mode);
};
#endif
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