52 lines
1.5 KiB
GLSL
52 lines
1.5 KiB
GLSL
#version 330
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// pathfinder/shaders/tile_alpha_porterduff.fs.glsl
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//
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// Copyright © 2020 The Pathfinder Project Developers.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Porter-Duff blend modes not supported by the standard GPU blender.
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#extension GL_GOOGLE_include_directive : enable
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#define PORTER_DUFF_FACTOR_ZERO 0
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#define PORTER_DUFF_FACTOR_DEST_ALPHA 1
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#define PORTER_DUFF_FACTOR_SRC_ALPHA 2
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#define PORTER_DUFF_FACTOR_ONE_MINUS_DEST_ALPHA 3
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precision highp float;
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uniform int uDestFactor;
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uniform int uSrcFactor;
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out vec4 oFragColor;
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#include "tile_alpha_sample.inc.glsl"
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vec4 getFactor(int factor, vec4 destRGBA, vec4 srcRGBA) {
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if (factor == PORTER_DUFF_FACTOR_ZERO)
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return vec4(0.0);
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if (factor == PORTER_DUFF_FACTOR_DEST_ALPHA)
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return vec4(destRGBA.a);
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if (factor == PORTER_DUFF_FACTOR_SRC_ALPHA)
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return vec4(srcRGBA.a);
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return vec4(1.0 - destRGBA.a);
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}
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void main() {
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vec4 srcRGBA = sampleSrcColor();
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vec4 destRGBA = sampleDestColor();
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vec4 destFactor = getFactor(uDestFactor, destRGBA, srcRGBA);
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vec4 srcFactor = getFactor(uSrcFactor, destRGBA, srcRGBA);
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vec4 blended = destFactor * destRGBA * vec4(destRGBA.aaa, 1.0) +
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srcFactor * srcRGBA * vec4(srcRGBA.aaa, 1.0);
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oFragColor = blended;
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}
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