How to change this javascript code to show a modified image?

I am playing with image color quantization algorithms. I have found this link

Color Thief

where a javascript (a language that I have never studied) implementation of a modified median cut algorithm is presented. But the demo shows just the ten dominant colors.

I would like to see what the quantized image looks like. In the file src/color-thief.js (line 132), there is a call to the quantization function. This functions returns a CMap object, which can be used to extract the dominant colors and to map a color to the best one in the reduced color palette. Given the CMap object, how do I modify the original image and show it?

Edit 1

This question is not about color quantization algorithms, but what i need to change in the Color Thief project in order to show a modified image. Suppose that, when i click the 'Click' button, i want to show the image after adding to all its pixels the value 10.

Here, I made this just for you.

I assume you want to simplify colors of an image to its palette provided by color-thief.

To achieve this I used color-thief and nearest-color.

Basically, you want to generate a color-thief's palette, then loop each pixel and get a closest palette value compared to the color of this pixel.

Check out this solution on codepen, code below:

/* rgbToHex() and leadingZero() functions ripped from nearest-color. */
function rgbToHex(rgb) {
  return '#' + leadingZero(rgb.r.toString(16)) +
     leadingZero(rgb.g.toString(16)) + leadingZero(rgb.b.toString(16));
}

function leadingZero(value) {
  if (value.length === 1) value = '0' + value;   
  return value;
}

/* Initialize an image and the canvas. */
var img = document.getElementById("img");
var canvas = document.getElementById("canvas");

/* When the image is loaded */
img.onload = function(){

  /* Initialize color-thief and get a palette from image. */
  var colorthief = new ColorThief(); 
  var colorthief_palette = colorthief.getPalette(img, 8);
  var palette = {};

  /* Turn color-thief palette to nearest-color-compatible palette. */
  for(var i = 0; i < colorthief_palette.length; i++){
    var r = colorthief_palette[i][0];
    var g = colorthief_palette[i][1]; 
    var b = colorthief_palette[i][2];
    var o = {r: r, g: g, b: b};
    palette["color_" + i] = rgbToHex(o);
  }

  /* Initialize nearest-color */
  var clr = nearestColor.from(palette);

  /* Initialize canvas, draw the image data and hide the default image. */
  var ctx = canvas.getContext("2d");
  canvas.width = img.width;
  canvas.height = img.height;  
  ctx.drawImage(img, 0, 0);
  img.style.display = "none"; 

  var data = ctx.getImageData(0, 0, canvas.width, canvas.height);
  var pixel = data.data;

  /* Loop for each pixel of image. */
  for (var i = 0, n = pixel.length; i < n; i += 4) {

      var r = pixel[i+0];
      var g = pixel[i+1]; 
      var b = pixel[i+2];
      var o = {r: r, g: g, b: b};
      var color = rgbToHex(o);
      var nearest = clr(color);

      pixel[i+0] = nearest.rgb.r;
      pixel[i+1] = nearest.rgb.g;
      pixel[i+2] = nearest.rgb.b;


  } 

  ctx.putImageData(data, 0, 0);

}

In result, this image:

Becomes this image: