Terrarum/assets/4096_bayer.frag

varying vec4 v_color;
varying vec2 v_texCoords;
uniform sampler2D u_texture;



//uniform mat4 bayer;
uniform float monitorGamma; // give 2.2f

int bayer[8][8] = {
{ 0, 32, 8, 40, 2, 34, 10, 42},   // 8x8 bayer ordered dithering
{48, 16, 56, 24, 50, 18, 58, 26}, // pattern. Each input pixel
{12, 44, 4, 36, 14, 46, 6, 38},   // is scaled to the 0..63 range
{60, 28, 52, 20, 62, 30, 54, 22}, // before looking in this table
{ 3, 35, 11, 43, 1, 33, 9, 41},   // to determine the action
{51, 19, 59, 27, 49, 17, 57, 25},
{15, 47, 7, 39, 13, 45, 5, 37},
{63, 31, 55, 23, 61, 29, 53, 21} }; // fun fact: you can calculate bayer value on-the-fly but LUT is faster
float bayerSize = 8.0;
float bayerDivider = bayerSize * bayerSize;


vec4 nearestColour(vec4 incolor) {
    vec4 rgbaCounts = vec4(16.0, 16.0, 16.0, 1.0);


    vec4 color = incolor;

    color.r = floor((rgbaCounts.r - 1.0) * color.r + 0.5) / (rgbaCounts.r - 1.0);
    color.g = floor((rgbaCounts.g - 1.0) * color.g + 0.5) / (rgbaCounts.g - 1.0);
    color.b = floor((rgbaCounts.b - 1.0) * color.b + 0.5) / (rgbaCounts.b - 1.0);

    if (rgbaCounts.a >= 2.0) {
        color.a = floor((rgbaCounts.a - 1.0) * color.a + 0.5) / (rgbaCounts.a - 1.0);
    }
    else if (rgbaCounts.a == 1.0) {
        color.a = (color.a >= 0.5f) ? 1.0 : 0.0;
    }
    else {
        color.a = 1.0;
    }

    return color;
}

void main(void) {
    // create texture coordinates based on pixelSize //
    vec4 inColor = texture2D(u_texture, v_texCoords);

    vec2 entry = mod(gl_FragCoord.xy, vec2(bayerSize, bayerSize));

    float r = 1.0 / monitorGamma;

    gl_FragColor = nearestColour(inColor + r * (bayer[int(entry.y)][int(entry.x)] / bayerDivider - 0.5));
    //gl_FragColor = nearestColour(inColor);
}