Canvas - Image

HTML

<canvas width="300" height="300" id="my-canvas">
</canvas>

CSS

body{
  background-color:black;
}
canvas{
  background-color:white;
}

JavaScript

var canvas = document.getElementById('my-canvas');
var ctx = canvas.getContext('2d');

var img = new Image();
img.onload = function() {
		var x1 = 100, x2 = 200, y1 = 100, y2=200;
		var w = img.width;
    var h = img.height;
    canvas.width = x2 - x1 ;
    canvas.height = y2 - y1;
    ctx.drawImage (img,-x1,-y1);
    console.log(canvas.toDataURL());
}
img.src = "http://www.w3.org/html/logo/downloads/HTML5_Logo_256.png";