pathfinder/shaders/mask_evenodd.fs.glsl

#version 330

// pathfinder/shaders/mask_evenodd.fs.glsl
//
// Copyright © 2020 The Pathfinder Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

precision highp float;

uniform sampler2D uFillTexture;

in vec2 vFillTexCoord;
in float vBackdrop;

out vec4 oFragColor;

void main() {
    float alpha = texture(uFillTexture, vFillTexCoord).r + vBackdrop;
    oFragColor = vec4(1.0 - abs(1.0 - mod(alpha, 2.0)));
}