import { isNodePattern } from '@jimp/utils';
/**
 * Apply a ordered dithering effect
 * @param {function(Error, Jimp)} cb (optional) a callback for when complete
 * @returns {Jimp} this for chaining of methods
 */

function dither(cb) {
  var rgb565Matrix = [1, 9, 3, 11, 13, 5, 15, 7, 4, 12, 2, 10, 16, 8, 14, 6];
  this.scanQuiet(0, 0, this.bitmap.width, this.bitmap.height, function (x, y, idx) {
    var thresholdId = ((y & 3) << 2) + x % 4;
    var dither = rgb565Matrix[thresholdId];
    this.bitmap.data[idx] = Math.min(this.bitmap.data[idx] + dither, 0xff);
    this.bitmap.data[idx + 1] = Math.min(this.bitmap.data[idx + 1] + dither, 0xff);
    this.bitmap.data[idx + 2] = Math.min(this.bitmap.data[idx + 2] + dither, 0xff);
  });

  if (isNodePattern(cb)) {
    cb.call(this, null, this);
  }

  return this;
}

export default (function () {
  return {
    dither565: dither,
    dither16: dither
  };
});
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