/* Binary threshold shader */

shader_type canvas_item;

uniform vec4 color_low: source_color = vec4(0.0, 0.0, 0.0, 1.0);
uniform vec4 color_hi: source_color = vec4(1.0, 1.0, 1.0, 1.0);

uniform float threshold: hint_range(0.0, 1.0) = 0.5;
uniform float contrast: hint_range(0.0, 1.0) = 1.0;
uniform float offset: hint_range(-1.0, 1.0) = 0.0;


void fragment() {
	vec3 screen_col = texture(TEXTURE, UV).rgb;

	// calculate pixel luminosity
	float luminosity = (screen_col.r * 0.299) + (screen_col.g * 0.587) + (screen_col.b * 0.114);

	// adjust contrast & offset
	luminosity = clamp((luminosity - 0.5 + offset) * contrast + 0.5, 0.0, 1.0);

	COLOR.rgba = luminosity > threshold ? color_hi : color_low;
}