5bde3f4b2f
I keep bumping into the need for this Change-Id: I69384f7d590c163fd6244bdc64cc5e48450fecd4 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/540171 Commit-Queue: Robert Phillips <robertphillips@google.com> Reviewed-by: Brian Osman <brianosman@google.com>
113 lines
4.1 KiB
C
113 lines
4.1 KiB
C
/*
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* Copyright 2016 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkBlendMode_DEFINED
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#define SkBlendMode_DEFINED
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#include "include/core/SkTypes.h"
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/**
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* Blends are operators that take in two colors (source, destination) and return a new color.
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* Many of these operate the same on all 4 components: red, green, blue, alpha. For these,
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* we just document what happens to one component, rather than naming each one separately.
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*
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* Different SkColorTypes have different representations for color components:
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* 8-bit: 0..255
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* 6-bit: 0..63
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* 5-bit: 0..31
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* 4-bit: 0..15
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* floats: 0...1
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*
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* The documentation is expressed as if the component values are always 0..1 (floats).
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*
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* For brevity, the documentation uses the following abbreviations
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* s : source
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* d : destination
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* sa : source alpha
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* da : destination alpha
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*
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* Results are abbreviated
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* r : if all 4 components are computed in the same manner
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* ra : result alpha component
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* rc : result "color": red, green, blue components
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*/
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enum class SkBlendMode {
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kClear, //!< r = 0
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kSrc, //!< r = s
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kDst, //!< r = d
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kSrcOver, //!< r = s + (1-sa)*d
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kDstOver, //!< r = d + (1-da)*s
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kSrcIn, //!< r = s * da
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kDstIn, //!< r = d * sa
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kSrcOut, //!< r = s * (1-da)
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kDstOut, //!< r = d * (1-sa)
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kSrcATop, //!< r = s*da + d*(1-sa)
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kDstATop, //!< r = d*sa + s*(1-da)
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kXor, //!< r = s*(1-da) + d*(1-sa)
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kPlus, //!< r = min(s + d, 1)
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kModulate, //!< r = s*d
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kScreen, //!< r = s + d - s*d
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kOverlay, //!< multiply or screen, depending on destination
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kDarken, //!< rc = s + d - max(s*da, d*sa), ra = kSrcOver
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kLighten, //!< rc = s + d - min(s*da, d*sa), ra = kSrcOver
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kColorDodge, //!< brighten destination to reflect source
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kColorBurn, //!< darken destination to reflect source
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kHardLight, //!< multiply or screen, depending on source
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kSoftLight, //!< lighten or darken, depending on source
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kDifference, //!< rc = s + d - 2*(min(s*da, d*sa)), ra = kSrcOver
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kExclusion, //!< rc = s + d - two(s*d), ra = kSrcOver
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kMultiply, //!< r = s*(1-da) + d*(1-sa) + s*d
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kHue, //!< hue of source with saturation and luminosity of destination
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kSaturation, //!< saturation of source with hue and luminosity of destination
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kColor, //!< hue and saturation of source with luminosity of destination
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kLuminosity, //!< luminosity of source with hue and saturation of destination
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kLastCoeffMode = kScreen, //!< last porter duff blend mode
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kLastSeparableMode = kMultiply, //!< last blend mode operating separately on components
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kLastMode = kLuminosity, //!< last valid value
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};
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static constexpr int kSkBlendModeCount = static_cast<int>(SkBlendMode::kLastMode) + 1;
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/**
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* For Porter-Duff SkBlendModes (those <= kLastCoeffMode), these coefficients describe the blend
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* equation used. Coefficient-based blend modes specify an equation:
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* ('dstCoeff' * dst + 'srcCoeff' * src), where the coefficient values are constants, functions of
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* the src or dst alpha, or functions of the src or dst color.
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*/
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enum class SkBlendModeCoeff {
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kZero, /** 0 */
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kOne, /** 1 */
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kSC, /** src color */
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kISC, /** inverse src color (i.e. 1 - sc) */
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kDC, /** dst color */
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kIDC, /** inverse dst color (i.e. 1 - dc) */
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kSA, /** src alpha */
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kISA, /** inverse src alpha (i.e. 1 - sa) */
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kDA, /** dst alpha */
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kIDA, /** inverse dst alpha (i.e. 1 - da) */
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kCoeffCount
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};
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/**
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* Returns true if 'mode' is a coefficient-based blend mode (<= kLastCoeffMode). If true is
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* returned, the mode's src and dst coefficient functions are set in 'src' and 'dst'.
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*/
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SK_API bool SkBlendMode_AsCoeff(SkBlendMode mode, SkBlendModeCoeff* src, SkBlendModeCoeff* dst);
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/** Returns name of blendMode as null-terminated C string.
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@return C string
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*/
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SK_API const char* SkBlendMode_Name(SkBlendMode blendMode);
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#endif
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