shader_type canvas_item;

uniform sampler2D screen_texture : hint_screen_texture;
uniform float grain_amount : hint_range(0.0, 1.0) = 0.05; // Adjust the amount of grain
uniform float grain_size : hint_range(0.1, 10.0) = 1.0; // Adjust the size of the grain
uniform bool animate = false;

//void fragment() {
	//// Sample the original screen texture
	//vec4 original_color = texture(screen_texture, SCREEN_UV);
	//
	//float noise = 0.0;
	//
	//if (animate) {
		//// Generate random noise
		//noise = (fract(sin(dot(UV * TIME, vec2(12.9898, 78.233))) * 43758.5453) - 0.5) * 2.0;
	//} else {
		 //noise = (fract(sin(dot(UV, vec2(12.9898, 78.233))) * 43758.5453) - 0.5) * 2.0;
	//}
	//// Add noise to the original color
	//original_color.rgb += noise * grain_amount * grain_size;
	//
	//// Clamp the final color to make sure it stays in the valid range
	//COLOR = clamp(original_color, 0.0, 1.0);
//}


// Feel free to steal this :^)
// Consider it MIT licensed, you can link to this page if you want to.

#define SHOW_NOISE 0
#define SRGB 0
// 0: Addition, 1: Screen, 2: Overlay, 3: Soft Light, 4: Lighten-Only
#define BLEND_MODE 4
#define SPEED 1.0
#define INTENSITY 0.05
// What gray level noise should tend to.
#define MEAN 0.0
// Controls the contrast/variance of noise.
#define VARIANCE 0.5

vec3 channel_mix(vec3 a, vec3 b, vec3 w) {
    return vec3(mix(a.r, b.r, w.r), mix(a.g, b.g, w.g), mix(a.b, b.b, w.b));
}

float gaussian(float z, float u, float o) {
    return (1.0 / (o * sqrt(2.0 * 3.1415))) * exp(-(((z - u) * (z - u)) / (2.0 * (o * o))));
}

vec3 madd(vec3 a, vec3 b, float w) {
    return a + a * b * w;
}

vec3 screen(vec3 a, vec3 b, float w) {
    return mix(a, vec3(1.0) - (vec3(1.0) - a) * (vec3(1.0) - b), w);
}

vec3 overlay(vec3 a, vec3 b, float w) {
    return mix(a, channel_mix(
        2.0 * a * b,
        vec3(1.0) - 2.0 * (vec3(1.0) - a) * (vec3(1.0) - b),
        step(vec3(0.5), a)
    ), w);
}

vec3 soft_light(vec3 a, vec3 b, float w) {
    return mix(a, pow(a, pow(vec3(2.0), 2.0 * (vec3(0.5) - b))), w);
}

void fragment() {
    vec2 ps = vec2(1.0) / (1.0 / SCREEN_PIXEL_SIZE).xy;
    vec2 uv = SCREEN_UV; //coord * ps;
    COLOR = texture(screen_texture, uv);
    #if SRGB
    color = pow(color, vec4(2.2));
    #endif

    float t = TIME * float(SPEED);
    float seed = dot(uv, vec2(12.9898, 78.233));
    float noise = fract(sin(seed) * 43758.5453 + t);
    noise = gaussian(noise, float(MEAN), float(VARIANCE) * float(VARIANCE));

    #if SHOW_NOISE
    COLOR = vec4(noise);
    #else
    // Ignore these mouse stuff if you're porting this
    // and just use an arbitrary intensity value.
    float w = float(INTENSITY);

    vec3 grain = vec3(noise) * (1.0 - COLOR.rgb);

    #if BLEND_MODE == 0
    COLOR.rgb += grain * w;
    #elif BLEND_MODE == 1
    COLOR.rgb = screen(COLOR.rgb, grain, w);
    #elif BLEND_MODE == 2
    COLOR.rgb = overlay(COLOR.rgb, grain, w);
    #elif BLEND_MODE == 3
    COLOR.rgb = soft_light(COLOR.rgb, grain, w);
    #elif BLEND_MODE == 4
    COLOR.rgb = max(COLOR.rgb, grain * w);
    #endif

    #if SRGB
    COLOR = pow(COLOR, vec4(1.0 / 2.2));
    #endif
    #endif
}