Palette Limiter Shader

Overview:

Screen reading shader which limits the colors in the viewport to a palette you provide. The shader works by picking the color within the palette that is the most similar to each pixel. Can just grab a palette off of something like Lospec and instantly get a cohesive visual style.

How to use:

• Place the shader material onto a SubViewPort Container
• Download or create a palette, then load it into the Palette Texture parameter
• Make sure to set the Num Colors parameter to however many colors are in your palette!

(Palette used in example is https://lospec.com/palette-list/slso8)

Shader code

shader_type canvas_item;
uniform int num_colors: hint_range(2,16) = 8;
uniform sampler2D PALETTE_TEXTURE: hint_default_black;

vec3 palette_limiter (in vec3 albedo){
	float estimation_cutoff = 0.001;
	vec3 closest_color;
	float min_dist = 2.0;
	float n = float(num_colors);
	
	for (int i=0; i<num_colors; i++ ){
		float index = 1.000/(2.000*n)+float(i)/n;
		vec3 index_color = texture(PALETTE_TEXTURE, vec2(index,0.5)).rgb;
		float dist = length(index_color - albedo);
		if (dist < min_dist) {
			min_dist = dist;
			closest_color = index_color;
			if (min_dist < estimation_cutoff){
				return closest_color;
			}
		}
	}
	return closest_color;
}

void fragment() {
	COLOR.rgb = palette_limiter(texture(TEXTURE,UV).rgb);
}