Threshold.js

define([
  'pex/fx/FXStage',
  'lib/text!pex/fx/Threshold.glsl'
], function (FXStage, ThresholdGLSL) {
  FXStage.prototype.threshold = function (options) {
    options = options || {};
    threshold = options.threshold !== undefined ? options.threshold : 0.5;
    var outputSize = this.getOutputSize(options.width, options.height);
    var rt = this.getRenderTarget(outputSize.width, outputSize.height, options.depth, options.bpp);
    rt.bind();
    this.getSourceTexture().bind();
    var program = this.getShader(ThresholdGLSL);
    program.use();
    program.uniforms.threshold(threshold);
    this.drawFullScreenQuad(outputSize.width, outputSize.height, null, program);
    rt.unbind();
    return this.asFXStage(rt, 'threshold');
  };
});