rust-roguelike-tutorial/resources/scanlines.fs

#version 330 core
out vec4 FragColor;

in vec2 TexCoords;

uniform sampler2D screenTexture;
uniform vec3 screenSize;
uniform bool screenBurn;

void main()
{
    vec3 col = texture(screenTexture, TexCoords).rgb;
    float scanLine = mod(gl_FragCoord.y, 2.0) * 0.25;
    vec3 scanColor = col.rgb - scanLine;

    if (col.r < 0.1f && col.g < 0.1f && col.b < 0.1f) {
        if (screenBurn) {
            float dist = (1.0 - distance(vec2(gl_FragCoord.x / screenSize.x, gl_FragCoord.y / screenSize.y), vec2(0.5,0.5))) * 0.2;
            FragColor = vec4(0.0, dist, dist, 1.0);
        } else {
            FragColor = vec4(0.0, 0.0, 0.0, 1.0);
        }
    } else {
        FragColor = vec4(scanColor, 1.0);
    }
}