Example of Canny edge detection algorithm in javascript

This is an implementation Canny Edge Detection algorithm in JavaScript. It's really just for fun. The story behind it is - I found an old faculty project written in C#, and decided to rewrite it in JS. I did it one evening, and it works! :D

P.S. You can see the original C# implementation we did here - https://github.com/petarjs/cs-canny-edge-detector!

See it in action at
https://petarjs.github.io/js-canny-edge-detector/

First, you load the worker:

let worker = new Worker('./dist/worker.js')

Then, to set up the worker, you need to send the command appData.

worker.postMessage({
  cmd: 'appData',
  data: {
    width: window.appData.width,
    height: window.appData.height,
    ut: window.appData.ut,
    lt: window.appData.lt
  } 
})

The command requires the following settings in the data object:

• width - Width of the image we're going to work on
• height - Height of the image we're going to work on
• ut - Upper treshold for edge detection
• lt - Lower treshold for edge detection

Setting ut and lt allows you to make them configurable from the UI. If ut and lt are not provided, tresholds will be automatically determined.

Finally, you need to provide the image to work on to the worker:

worker.postMessage({
  cmd: 'imgData',
  data: pixels
})

pixels must be of type ImageData. You can get it from the canvas into which the image is loaded:

const imgd = canvasFrom
    .getContext('2d')
    .getImageData(0, 0, width, height)

const imageData = imgd.data

Not sure why you'd use this in a project, but if you really really want to... With npm installed, run

$ npm install petarjs/js-canny-edge-detector

And refer to the index.html in the repo to find the example of usage.

• Canny Edge Detector on Wikipedia
• Implementation with similar results as this one
• Another, more awesome implementation

MIT