/**
 * Gaussian
 * By Raphael Rouvinov-Kats
 * 
 * Sort of draws gaussian distribution values
 * https://en.wikipedia.org/wiki/Multivariate_normal_distribution
 * 
 * But it's equal at all angles, so it's just a normal distribution
 * https://en.wikipedia.org/wiki/Normal_distribution
 * */

frameRate(0);

var normalPDF = function(x, mu, sigma) {
    return 1/sqrt(2*PI*sigma*sigma) * pow(Math.E, -(x-mu)*(x-mu)/(2*sigma*sigma));
};

var addGaussianAtPosition = function(posX, posY) {
    if (!this.loadPixels) { return; }
    this.loadPixels();
    var pix=this.imageData.data;
    
    var RED = 0, GREEN = 1, BLUE = 2;
    var colToSubtract;
    
    var r = random(0, 1);
    if      (r < 1/3) { colToSubtract = RED; }
    else if (r < 2/3) { colToSubtract = GREEN; }
    else              { colToSubtract = BLUE; }
    
    var l = 401 * 401;
    while(l--) {
        var x = l % 401;
        var y = (l-x)/401;
        var dx = posX - x;
        var dy = posY - y;
        
        var d = sqrt(dx*dx + dy*dy);
        var val = normalPDF(d, 0, 100) * (1 << 16);
        
        var ind = (x + y * 400) << 2;
        pix[ind + colToSubtract] -= val;
    }
    
    this.updatePixels();
};

var mousePressed = function() {
    addGaussianAtPosition(mouseX, mouseY);
};