Question

I’ve been Googling around a bit for an answer and haven’t found a definitive one either way: is it possible to play a video using an HTML5 canvas, and also allow the user to draw on this video? The use case, for some context, is to play a video on infinite loop so the user can draw multiple boxes over specific areas to indicate regions of interest.

As a bonus (:P), if I can figure out how to do this on its own, any hints as to how this could be done within Drupal? I’m already looking at the Canvas Field module, but if you have any hints on this point too (though the first one is the priority), that’d be awesome!

Answer 1

You can draw html5 video elements onto a canvas. The drawImage method accepts a video element in the first parameter just like an image element. This will take the current “frame” of the video element and render it onto the canvas. To get fluid playback of the video you will need to draw the video to the canvas repeatedly.

You can then draw on the canvas normally, making sure you redraw everything after each update of the video frame.

Here is a demo of video on canvas

here is a in-depth look into video and the canvas