Get dominant color from specific area

[jmcbee]

Hi, is it possible to only get the dominant color from a specific area in an image?

var canvas = document.getElementById('da-canvas');
var context = canvas.getContext('2d');
var img = new Image();
var colorThief = new ColorThief();
var bg;

img.src = 'images/thefame.jpg';
img.onload = function() {
  canvas.height = 10;
  canvas.width = this.width;
  context.drawImage(img, 0, 0, this.width, this.height);
  bg = colorThief.getColor(canvas);
  canvas.height = this.height;
  context.drawImage(img, 0, 0, this.width, this.height);
  document.getElementById('container').style.background = 'rgb(' + bg.join(',') + ')';
}

I'm trying to get only 10px from the top of the image. I thought just setting the height of the canvas will work hahaha. But it didn't.

I think this might increase the speed as well?

[jmcbee]

Here's the image I'm trying to use with this library:

Which results to rgb [38, 40, 50].

[ksubileau]

Duplicate, see #44