konva/src/filters/Threshold.js

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(function() {
  'use strict';
  /**
     * Threshold Filter. Pushes any value above the mid point to
     *  the max and any value below the mid point to the min.
     *  This affects the alpha channel.
     * @function
     * @name Threshold
     * @memberof Konva.Filters
     * @param {Object} imageData
     * @author ippo615
     * @example
     * node.cache();
     * node.filters([Konva.Filters.Threshold]);
     * node.threshold(0.1);
     */

  Konva.Filters.Threshold = function(imageData) {
    var level = this.threshold() * 255,
      data = imageData.data,
      len = data.length,
      i;

    for (i = 0; i < len; i += 1) {
      data[i] = data[i] < level ? 0 : 255;
    }
  };

  Konva.Factory.addGetterSetter(
    Konva.Node,
    'threshold',
    0.5,
    null,
    Konva.Factory.afterSetFilter
  );
  /**
    * get/set threshold.  Must be a value between 0 and 1. Use with {@link Konva.Filters.Threshold} or {@link Konva.Filters.Mask} filter.
    * @name threshold
    * @method
    * @memberof Konva.Node.prototype
    * @param {Number} threshold
    * @returns {Number}
    */
})();