How to take screenshot of a div with JavaScript?

Question

I am building something called the "HTML Quiz". It's completely ran on JavaScript and it's pretty cool.

At the end, a results box pops up that says "Your Results:" and it shows how much time they took, what percentage they got, and how many questions they got right out of 10. I would like to have a button that says "Capture results" and have it somehow take a screenshot or something of the div, and then just show the image captured on the page where they can right click and "Save image as."

I really would love to do this so they can share their results with others. I don't want them to "copy" the results because they can easily change that. If they change what it says in the image, oh well.

Does anyone know a way to do this or something similar?

Answer 1

No, I don't know of a way to 'screenshot' an element, but what you could do, is draw the quiz results into a canvas element, then use the HTMLCanvasElement object's toDataURL function to get a data: URI with the image's contents.

When the quiz is finished, do this:

var c = document.getElementById('the_canvas_element_id');
var t = c.getContext('2d');
/* then use the canvas 2D drawing functions to add text, etc. for the result */

When the user clicks "Capture", do this:

window.open('', document.getElementById('the_canvas_element_id').toDataURL());

This will open a new tab or window with the 'screenshot', allowing the user to save it. There is no way to invoke a 'save as' dialog of sorts, so this is the best you can do in my opinion.