index.js

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

/**
 * Creates a circle out of an image.
 * @param {object} options (optional) r: radius of effect
 * @param {function(Error, Jimp)} cb (optional) a callback for when complete
 * @returns {Jimp} this for chaining of methods
 */
export default () => ({
  fisheye(options = { r: 2.5 }, cb) {
    if (typeof options === 'function') {
      cb = options;
      options = { r: 2.5 };
    }

    const source = this.cloneQuiet();
    const { width, height } = source.bitmap;

    source.scanQuiet(0, 0, width, height, (x, y) => {
      const hx = x / width;
      const hy = y / height;
      const r = Math.sqrt(Math.pow(hx - 0.5, 2) + Math.pow(hy - 0.5, 2));
      const rn = 2 * Math.pow(r, options.r);
      const cosA = (hx - 0.5) / r;
      const sinA = (hy - 0.5) / r;
      const newX = Math.round((rn * cosA + 0.5) * width);
      const newY = Math.round((rn * sinA + 0.5) * height);
      const color = source.getPixelColor(newX, newY);

      this.setPixelColor(color, x, y);
    });

    /* Set center pixel color, otherwise it will be transparent */
    this.setPixelColor(
      source.getPixelColor(width / 2, height / 2),
      width / 2,
      height / 2
    );

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

    return this;
  }
});