index.js

import { isNodePattern, throwError } from '@jimp/utils';

/**
 * Flip the image horizontally
 * @param {boolean} horizontal a Boolean, if true the image will be flipped horizontally
 * @param {boolean} vertical a Boolean, if true the image will be flipped vertically
 * @param {function(Error, Jimp)} cb (optional) a callback for when complete
 * @returns {Jimp} this for chaining of methods
 */
function flipFn(horizontal, vertical, cb) {
  if (typeof horizontal !== 'boolean' || typeof vertical !== 'boolean')
    return throwError.call(
      this,
      'horizontal and vertical must be Booleans',
      cb
    );

  const bitmap = Buffer.alloc(this.bitmap.data.length);
  this.scanQuiet(0, 0, this.bitmap.width, this.bitmap.height, function(
    x,
    y,
    idx
  ) {
    const _x = horizontal ? this.bitmap.width - 1 - x : x;
    const _y = vertical ? this.bitmap.height - 1 - y : y;
    const _idx = (this.bitmap.width * _y + _x) << 2;
    const data = this.bitmap.data.readUInt32BE(idx);

    bitmap.writeUInt32BE(data, _idx);
  });

  this.bitmap.data = Buffer.from(bitmap);

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

  return this;
}

export default () => ({
  flip: flipFn,
  mirror: flipFn
});