shader_type canvas_item;

#define pow2(x) (x * x)
#define iResolution vec2(0.001,0.001)

uniform sampler2D iChannel0;
uniform vec2 rotationpivot=vec2(0.5,0.5);
uniform float speed=0.1;
uniform float strength : hint_range(0.0, 20.0, 0.1) = 1.0;
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 * pow2(sigma)) * exp(-((pow2(i.x) + pow2(i.y)) / (2.0 * pow2(sigma))));
}

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;
}

vec2 rotateUV(vec2 uv, vec2 pivot, float rotation) {
	float cosa = cos(rotation);
	float sina = sin(rotation);
	uv -= pivot;
	return vec2(
		cosa * uv.x - sina * uv.y,
		cosa * uv.y + sina * uv.x 
	) + pivot;
}


void fragment() {
	
	vec2 uv = UV ;
	vec2 rotuv=rotateUV(uv,rotationpivot,TIME*speed);
	
	float _strength=abs(0.47-uv.y)*strength;
    vec2 ps = vec2(1.0) / iResolution.xy * .000001 * _strength;
    
	
	//COLOR.rgb=texture(iChannel0, uv).rgb;
    
    COLOR.rgb = blur(iChannel0, rotuv, ps );
    COLOR.a = 1.0;
}