jquery - POST Javascript generated file -

using fabric.js, adding text overlays user's local image, , shoving

<img src="" id="pic" style="display: none;"> 

now, need post server.i know how upload files justing html ,

<input type="file" id="popup_chooser" name="something"> 

however, cannot figure out how $('#pic').attr('src') post variable.

how best way go doing this? thanks

if understand question right :

$('#popup_chooser').val($('#pic').attr('src'));