Javascript Canvas edge detection

Question

I would like to achieve this kind of image processing effect in Canvas :

WebGL image processing

What i need is an edge detection algorithm or explanation to draw only black pixels or border element ( such as a face for example ) of the image that an user can submit.

cheers

Answer 1

Following your idea, the first step is the Edge detection. The example below shows hot to detect edges using MarvinJ. Having the edges, you might get the object contour.

Input Image:

Edge Detection:

var canvas = document.getElementById("canvas");

image = new MarvinImage();
image.load("https://i.imgur.com/ZHgkM9w.jpg", imageLoaded);

function imageLoaded(){
  var imageOut = new MarvinImage(image.getWidth(), image.getHeight());
  
  // Edge Detection (Prewitt approach)
  Marvin.prewitt(image, imageOut);
  // Invert color
  Marvin.invertColors(imageOut, imageOut);
  // Threshold
  Marvin.thresholding(imageOut, imageOut, 220);
  imageOut.draw(canvas); 
}

<script src="https://www.marvinj.org/releases/marvinj-0.7.js"></script>
<canvas id="canvas" width="500" height="344"></canvas>