Cropping Image with JavaScript and Canvas

Below is an example of how to crop image using JavaScript and HTML Canvas element.

var canvas = document.createElement('canvas');
canvas.width = 150;
canvas.height = 150;
//var canvas = document.getElementById('myCanvas');  // create a new canvas or use the existing one in document

var context = canvas.getContext('2d');

var sourceImg = new Image();

sourceImg.onload = function () {    // make sure the image is loaded first before cropping it

 context.drawImage(sourceImg, source_starting_x_coord, source_starting_y_coord, 
  width_to_be_cropped_from_source_coord, height_to_be_cropped_from_source_coord, 
  starting_x_coord_on_destination_canvas, starting_y_coord_on_destination_canvas, 
  width_of_cropped_image_to_put_on_canvas, heigth_of_cropped_image_to_put_on_canvas);
 //context.drawImage(sourceImg, 0, 50, 150, 150, 0, 0, 150, 150);

 // display or do anything we like with the result
 //imageDisplay = canvas.toDataURL();

}

sourceImg.src = toBeCroppedImageSource;  // can be an image url or base-64 encoded data