Source: filters/convolution/ConvolutionFilter.js

var core = require('../../core');
// @see https://github.com/substack/brfs/issues/25
var fs = require('fs');

/**
 * The ConvolutionFilter class applies a matrix convolution filter effect.
 * A convolution combines pixels in the input image with neighboring pixels to produce a new image.
 * A wide variety of image effects can be achieved through convolutions, including blurring, edge
 * detection, sharpening, embossing, and beveling. The matrix should be specified as a 9 point Array.
 * See http://docs.gimp.org/en/plug-in-convmatrix.html for more info.
 *
 * @class
 * @extends PIXI.AbstractFilter
 * @memberof PIXI.filters
 * @param matrix {number[]} An array of values used for matrix transformation. Specified as a 9 point Array.
 * @param width {number} Width of the object you are transforming
 * @param height {number} Height of the object you are transforming
 */
function ConvolutionFilter(matrix, width, height)
{
    core.AbstractFilter.call(this,
        // vertex shader
        null,
        // fragment shader
        fs.readFileSync(__dirname + '/convolution.frag', 'utf8'),
        // custom uniforms
        {
            matrix:     { type: '1fv', value: new Float32Array(matrix) },
            texelSize:  { type: 'v2', value: { x: 1 / width, y: 1 / height } }
        }
    );
}

ConvolutionFilter.prototype = Object.create(core.AbstractFilter.prototype);
ConvolutionFilter.prototype.constructor = ConvolutionFilter;
module.exports = ConvolutionFilter;

Object.defineProperties(ConvolutionFilter.prototype, {
    /**
     * An array of values used for matrix transformation. Specified as a 9 point Array.
     *
     * @member {number[]}
     * @memberof PIXI.filters.ConvolutionFilter#
     */
    matrix: {
        get: function ()
        {
            return this.uniforms.matrix.value;
        },
        set: function (value)
        {
            this.uniforms.matrix.value = new Float32Array(value);
        }
    },

    /**
     * Width of the object you are transforming
     *
     * @member {number}
     * @memberof PIXI.filters.ConvolutionFilter#
     */
    width: {
        get: function ()
        {
            return 1/this.uniforms.texelSize.value.x;
        },
        set: function (value)
        {
            this.uniforms.texelSize.value.x = 1/value;
        }
    },

    /**
     * Height of the object you are transforming
     *
     * @member {number}
     * @memberof PIXI.filters.ConvolutionFilter#
     */
    height: {
        get: function ()
        {
            return 1/this.uniforms.texelSize.value.y;
        },
        set: function (value)
        {
            this.uniforms.texelSize.value.y = 1/value;
        }
    }
});