shader_type canvas_item;

#define pow2(x) (x * x)
#define iResolution 1.0/SCREEN_PIXEL_SIZE

uniform sampler2D gradient : source_color, filter_nearest; 
uniform int dimension;

const float alpha = 0.3;
const float strength = 0.5;
const float pi = atan(1.0) * 4.0;
const int samples = 35;
const float sigma = float(samples) * 0.25;

float gaussian(vec2 i) {
    return 1.0 / (2.0 * pi * pow(sigma,2)) * exp(-((pow(i.x,2) + pow(i.y,2)) / (2.0 * pow(sigma,2))));
}

vec3 blur(sampler2D sp, vec2 uv, vec2 scale) {
    vec3 col = vec3(0.0);
    float accum = 0.0;
    float weight;
    vec2 offset;
    
    for (int x = -samples / 2; x < samples / 2; ++x) {
        for (int y = -samples / 2; y < samples / 2; ++y) {
            offset = vec2(float(x), float(y));
            weight = gaussian(offset);
            col += texture(sp, uv + scale * offset).rgb * weight;
            accum += weight;
        }
    }
    
    return col / accum;
}

void fragment() {
	vec2 ps = vec2(1.0) / iResolution.xy * .000001 * strength;
    vec2 uv = UV ;
	
	vec3 pixel_color = blur(TEXTURE, uv, ps );
	float value = pixel_color.x;
	if (dimension == 1) value = pixel_color.y;
	if (dimension == 2) value = pixel_color.z;
	
	COLOR = texture(gradient, vec2(value, 0));
	COLOR.a = alpha;
}