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#version 300 es
// Posterization Shader - OPTIMIZED
// Fixes: Proper rounding, optional dithering to reduce banding
precision highp float;
in vec2 v_texcoord;
uniform sampler2D tex;
out vec4 fragColor;
// --- CONFIGURATION ---
const float COLOR_LEVELS = 4.0;
// Enable dithering to reduce visible banding
const bool DITHER = true;
// Simple dither pattern
float dither(vec2 pos) {
// 4x4 Bayer matrix approximation
vec2 p = fract(pos * 0.5);
float d = fract(dot(p, vec2(0.75, 0.5)));
return (d - 0.5) / COLOR_LEVELS;
}
void main() {
vec4 color = texture(tex, v_texcoord);
vec3 posterized;
if (DITHER) {
// Add dither noise before quantization
float ditherValue = dither(gl_FragCoord.xy);
posterized = floor((color.rgb + ditherValue) * COLOR_LEVELS + 0.5) / COLOR_LEVELS;
} else {
// FIXED: Use round() behavior instead of floor() for better color accuracy
posterized = floor(color.rgb * COLOR_LEVELS + 0.5) / COLOR_LEVELS;
}
posterized = clamp(posterized, 0.0, 1.0);
fragColor = vec4(posterized, color.a);
}
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