52 lines
1.7 KiB
JavaScript
52 lines
1.7 KiB
JavaScript
// the code is taken from https://github.com/mattlockyer/iat455/blob/6493c882f1956703133c1bffa1d7ee9a83741cbe/assignment1/assignment/effects/blur-effect-dyn.js
|
|
// (c) Matt Lockyer, https://github.com/mattlockyer
|
|
|
|
function hypotenuse(x1, y1, x2, y2) {
|
|
var xSquare = Math.pow(x1 - x2, 2);
|
|
var ySquare = Math.pow(y1 - y2, 2);
|
|
return Math.sqrt(xSquare + ySquare);
|
|
}
|
|
|
|
/*
|
|
* Generates a kernel used for the gaussian blur effect.
|
|
*
|
|
* @param dimension is an odd integer
|
|
* @param sigma is the standard deviation used for our gaussian function.
|
|
*
|
|
* @returns an array with dimension^2 number of numbers, all less than or equal
|
|
* to 1. Represents our gaussian blur kernel.
|
|
*/
|
|
function generateGaussianKernel(dimension, sigma) {
|
|
if (!(dimension % 2) || Math.floor(dimension) !== dimension || dimension<3) {
|
|
throw new Error(
|
|
'The dimension must be an odd integer greater than or equal to 3'
|
|
);
|
|
}
|
|
var kernel = [];
|
|
|
|
var twoSigmaSquare = 2 * sigma * sigma;
|
|
var centre = (dimension - 1) / 2;
|
|
|
|
for (var i = 0; i < dimension; i++) {
|
|
for (var j = 0; j < dimension; j++) {
|
|
var distance = hypotenuse(i, j, centre, centre);
|
|
|
|
// The following is an algorithm that came from the gaussian blur
|
|
// wikipedia page [1].
|
|
//
|
|
// http://en.wikipedia.org/w/index.php?title=Gaussian_blur&oldid=608793634#Mechanics
|
|
var gaussian = (1 / Math.sqrt(
|
|
Math.PI * twoSigmaSquare
|
|
)) * Math.exp((-1) * (Math.pow(distance, 2) / twoSigmaSquare));
|
|
|
|
kernel.push(gaussian);
|
|
}
|
|
}
|
|
|
|
// Returns the unit vector of the kernel array.
|
|
var sum = kernel.reduce(function (c, p) { return c + p; });
|
|
return kernel.map(function (e) { return e / sum; });
|
|
}
|
|
|
|
module.exports = generateGaussianKernel;
|