Quantized Bayer dither

Quantized (multi–step) dither shader.

Description:

The number of steps can be set from quantize_groups uniform. Default is 2 (Ng=2).

Complete source codes:

Shader code

shader_type canvas_item;

uniform int quantize_groups : hint_range(1, 8) = 2;

const int DITHER_SIZE = 2;
const float DITHER_PATTERN[DITHER_SIZE * DITHER_SIZE] = {
	0.5 / 4.0, 2.5 / 4.0,
	3.5 / 4.0, 1.5 / 4.0 };

//const int DITHER_SIZE = 4;
//const float DITHER_PATTERN[DITHER_SIZE * DITHER_SIZE] = {
//     0.5 / 16.0,  8.5 / 16.0,  2.5 / 16.0, 10.5 / 16.0,
//    12.5 / 16.0,  4.5 / 16.0, 14.5 / 16.0,  6.5 / 16.0,
//     3.5 / 16.0, 11.5 / 16.0,  1.5 / 16.0,  9.5 / 16.0,
//    15.5 / 16.0,  7.5 / 16.0, 13.5 / 16.0,  5.5 / 16.0 };

//const int DITHER_SIZE = 8;
//const float DITHER_PATTERN[DITHER_SIZE * DITHER_SIZE] = {
//	 0.5 / 64.0, 48.5 / 64.0, 12.5 / 64.0, 60.5 / 64.0,  3.5 / 64.0, 51.5 / 64.0, 15.5 / 64.0, 63.5 / 64.0,
//	32.5 / 64.0, 16.5 / 64.0, 44.5 / 64.0, 28.5 / 64.0, 35.5 / 64.0, 19.5 / 64.0, 47.5 / 64.0, 31.5 / 64.0,
//	 8.5 / 64.0, 56.5 / 64.0,  4.5 / 64.0, 52.5 / 64.0, 11.5 / 64.0, 59.5 / 64.0,  7.5 / 64.0, 55.5 / 64.0,
//	40.5 / 64.0, 24.5 / 64.0, 36.5 / 64.0, 20.5 / 64.0, 43.5 / 64.0, 27.5 / 64.0, 39.5 / 64.0, 23.5 / 64.0,
//	 2.5 / 64.0, 50.5 / 64.0, 14.5 / 64.0, 62.5 / 64.0,  1.5 / 64.0, 49.5 / 64.0, 13.5 / 64.0, 61.5 / 64.0,
//	34.5 / 64.0, 18.5 / 64.0, 46.5 / 64.0, 30.5 / 64.0, 33.5 / 64.0, 17.5 / 64.0, 45.5 / 64.0, 29.5 / 64.0,
//	10.5 / 64.0, 58.5 / 64.0,  6.5 / 64.0, 54.5 / 64.0,  9.5 / 64.0, 57.5 / 64.0,  5.5 / 64.0, 53.5 / 64.0,
//	42.5 / 64.0, 26.5 / 64.0, 38.5 / 64.0, 22.5 / 64.0, 41.5 / 64.0, 25.5 / 64.0, 37.5 / 64.0, 21.5 / 64.0 };

void fragment()
{
	ivec2 p = ivec2(SCREEN_UV / SCREEN_PIXEL_SIZE) % ivec2(DITHER_SIZE);
	float g = float(quantize_groups);
	float t = DITHER_PATTERN[p.y * DITHER_SIZE + p.x];
	COLOR = (step(t, fract(COLOR * g)) + floor(COLOR * g)) / g;
}

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