diff --git a/js/x11/core/examples/smoketest/blur-convolution.js b/js/x11/core/examples/smoketest/blur-convolution.js new file mode 100644 index 0000000..7d85089 --- /dev/null +++ b/js/x11/core/examples/smoketest/blur-convolution.js @@ -0,0 +1,51 @@ +// 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;