image-sequencer/src/modules/Gradient/Module.js

const pixelSetter = require('../../util/pixelSetter.js'),
  pixelManipulation = require('../_nomodule/PixelManipulation');

module.exports = function Gradient(options, UI) {

  var defaults = require('./../../util/getDefaults.js')(require('./info.json'));
  options.gradientType = options.gradientType || defaults.gradientType;

  var output;

  // The function which is called on every draw.
  function draw(input, callback) {
    var step = this;

    function output(image, datauri, mimetype, wasmSuccess) {
      step.output = { src: datauri, format: mimetype, wasmSuccess, useWasm: options.useWasm };
    }

    function extraManipulation(pixels) {
      const [w, h] = pixels.shape;
      if (options.gradientType === 'linear') {
        for (var i = 0; i < w; i++) {
          for (var j = 0; j < h; j++) {
            let val = (i / w) * 255;
            
            pixelSetter(i, j, [val, val, val, 255], pixels);
          }
        }
      }
      else {
        for (var i = 0; i < w; i++) {
          for (var j = 0; j < h; j++) {
            var distX = Math.abs(w / 2 - i);
            var distY = Math.abs(h / 2 - j);
            var distance = Math.sqrt(Math.pow(distX, 2) + Math.pow(distY, 2));
            val = 255 * (distance / pixels.shape[0]);
            pixelSetter(i, j, [val, val, val, 255], pixels);
          }
        }
      }

      return pixels;
    }

    return pixelManipulation(input, {
      output,
      extraManipulation,
      callback,
      format: input.format,
      image: options.image,
      inBrowser: options.inBrowser,
      useWasm:options.useWasm
    });

  }

  return {
    options: options,
    draw: draw,
    output: output,
    UI: UI
  };
};