Blob Detection for Canvas

To get the blobs from a Canvas

blobs = Detector.getBlobsInCanvas(canvas)

Or, if you want more control, you can use an ImageData

blobs = Detector.getBlobs(imageData, threshold)

And draw the blobs like this

for (var i = 0; i < blobs.length; i++) {
	ctx.fillRect(blobs[i].minX, blobs[i].minY, blobs[i].width, blobs[i].height)
};

Working sample:

http://lucasdupin.github.io/jsBlobDetection