publiclab/image-sequencer

module.exports = function Dynamic(options, UI) {
  var defaults = require('./../../util/getDefaults.js')(require('./info.json'));
  var output;

  // This function is called on every draw.
  function draw(input, callback, progressObj) {

    progressObj.stop(true);
    progressObj.overrideFlag = true;

    var step = this;

    options.red = options.red || defaults.red;
    options.blue = options.blue || defaults.blue;
    options.green = options.green || defaults.green;

    const Parser = require('expr-eval').Parser;
    function generator(expression) {
      let expr = Parser.parse('R = r; G = g; B = b; A = a; ' + expression);
      return expr.toJSFunction("r,g,b,a,R,G,B,A");
    }
    
    var channels = ['red', 'green', 'blue', 'alpha'];

    channels.forEach(function(channel) {
      if (channel === 'alpha'){
        options['alpha_function'] = function() { return 255; };
      } else {
        options[channel + '_function'] = generator(options[channel]);
      }
    });

    function changePixel(r, g, b, a) {

      /* neighbourpixels can be calculated by
       this.getNeighbourPixel.fun(x,y)  or this.getNeighborPixel.fun(x,y)
       */
      var combined = (r + g + b) / 3.000;
      return [
        options.red_function(r, g, b, a),
        options.green_function(r, g, b, a),
        options.blue_function(r, g, b, a),
        options.alpha_function(r, g, b, a),
      ];
    }

    /* Functions to get the neighbouring pixel by position (x,y) */
    function getNeighbourPixel(pixels, curX, curY, distX, distY) {
      return [
        pixels.get(curX + distX, curY + distY, 0),
        pixels.get(curX + distX, curY + distY, 1),
        pixels.get(curX + distX, curY + distY, 2),
        pixels.get(curX + distX, curY + distY, 3)
      ];
    }

    // via P5js: https://github.com/processing/p5.js/blob/2920492842aae9a8bf1a779916893ac19d65cd38/src/math/calculation.js#L461-L472
    function map(n, start1, stop1, start2, stop2, withinBounds) {
      var newval = (n - start1) / (stop1 - start1) * (stop2 - start2) + start2;
      if (!withinBounds) {
        return newval;
      }
      // also via P5js: https://github.com/processing/p5.js/blob/2920492842aae9a8bf1a779916893ac19d65cd38/src/math/calculation.js#L116-L119
      function constrain(n, low, high) {
        return Math.max(Math.min(n, high), low);
      }
      if (start2 < stop2) {
        return constrain(newval, start2, stop2);
      } else {
        return constrain(newval, stop2, start2);
      }
    }

    function output(image, datauri, mimetype, wasmSuccess) {
      step.output = { src: datauri, format: mimetype, wasmSuccess, useWasm: options.useWasm };
    }
    
    return require('../_nomodule/PixelManipulation.js')(input, {
      output: output,
      ui: options.step.ui,
      changePixel: changePixel,
      getNeighbourPixel: getNeighbourPixel,
      getNeighborPixel: getNeighbourPixel,
      format: input.format,
      image: options.image,
      inBrowser: options.inBrowser,
      callback: callback,
      useWasm:options.useWasm
    });

  }

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