image-js/src/image/filter/gradientFilter.js

Image processing and manipulation in JavaScript

import convolution from '../operator/convolution';

/**
 * Direction of a gradient filter
 * @typedef {('x'|'y'|'xy')} GradientDirection
 */

/**
 * @memberof Image
 * @instance
 * @param {object} [options]
 * @param {GradientDirection} [options.direction]
 * @param {Array<Array<number>>} [options.kernelX]
 * @param {Array<Array<number>>} [options.kernelY]
 * @param {string} [options.border='copy']
 * @param {*} [options.channels]
 * @param {number} [options.bitDepth=this.bitDepth] Specify the bitDepth of the resulting image
 * @return {Image}
 */
export default function gradientFilter(options = {}) {
  let {
    direction = 'xy',
    border = 'copy',
    kernelX,
    kernelY,
    channels,
    bitDepth = this.bitDepth,
  } = options;

  this.checkProcessable('gradientFilter', {
    bitDepth: [8, 16],
  });

  switch (direction) {
    case 'x':
      if (!kernelX) throw new Error('kernelX option is missing');
      return convolution.call(this, kernelX, {
        channels: channels,
        border: border,
        bitDepth,
      });
    case 'y':
      if (!kernelY) throw new Error('kernelY option is missing');
      return convolution.call(this, kernelY, {
        channels: channels,
        border: border,
        bitDepth,
      });
    case 'xy': {
      if (!kernelX) throw new Error('kernelX option is missing');
      if (!kernelY) throw new Error('kernelY option is missing');
      const gX = convolution.call(this, kernelX, {
        channels: channels,
        border: border,
        bitDepth: 32,
      });
      const gY = convolution.call(this, kernelY, {
        channels: channels,
        border: border,
        bitDepth: 32,
      });
      return gX.hypotenuse(gY, { bitDepth, channels: channels });
    }
    default:
      throw new Error(`Unknown parameter direction: ${direction}`);
  }
}