I have a webapp with a canvas-element. I want to enable the user to tweet the picture by one single click. How to do this?

ton-upload
javascript
media-upload
tweetbutton

#1

Hello,
given a twitter user is logged in on twitter.com, and in another tab he is on my website, where he could change the content of a canvas element, I want to enable this user to tweet the canvas-content as image by a single click.
So let’s assume I already created an html image element out of the canvas-content. (var img;)
As get-requests are recommended not to exceed a certein length and for practicall purposes, I want to create a post-request to twitter.

Could you help me with how to create that request in javascript, please?
How to continue with the img, and where to send it to using XMLHttpRequest?
.