Source: gfx/filters/dropshadow/BlurYTintFilter.js

const AbstractFilter = require('../../core/renderers/webgl/filters/AbstractFilter');

/**
 * The BlurYTintFilter applies a vertical Gaussian blur to an object.
 *
 * @class
 * @extends AbstractFilter
 */
function BlurYTintFilter() {
  AbstractFilter.call(this,
        // vertex shader
        require('./blurYTint.vert'),
        // fragment shader
        require('./blurYTint.frag'),
        // set the uniforms
    {
      blur: { type: '1f', value: 1 / 512 },
      color: { type: 'c', value: [0,0,0] },
      alpha: { type: '1f', value: 0.7 },
      offset: { type: '2f', value:[5, 5] },
      strength: { type: '1f', value:1 },
    }
    );

  this.passes = 1;
  this.strength = 4;
}

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

BlurYTintFilter.prototype.applyFilter = function(renderer, input, output, clear) {
  var shader = this.getShader(renderer);

  this.uniforms.strength.value = this.strength / 4 / this.passes * (input.frame.height / input.size.height);

  if (this.passes === 1) {
    renderer.filterManager.applyFilter(shader, input, output, clear);
  }
  else {
    var renderTarget = renderer.filterManager.getRenderTarget(true);
    var flip = input;
    var flop = renderTarget;

    for (var i = 0; i < this.passes - 1; i++) {
      renderer.filterManager.applyFilter(shader, flip, flop, clear);

      var temp = flop;
      flop = flip;
      flip = temp;
    }

    renderer.filterManager.applyFilter(shader, flip, output, clear);

    renderer.filterManager.returnRenderTarget(renderTarget);
  }
};


Object.defineProperties(BlurYTintFilter.prototype, {
    /**
     * Sets the strength of both the blur.
     *
     * @member {number}
     * @memberof filters.BlurYTintFilter#
     * @default 2
     */
  blur: {
    get: function() {
      return this.strength;
    },
    set: function(value) {
      this.padding = value * 0.5;
      this.strength = value;
    },
  },
});