In System > On Canvas snapshot, the snapshot is already available, no need to load it via AJAX. And pasting an object is position sensitive, so the object needs to overlap the canvas in order to be pasted there. You can just set the position/size to the canvas > paste it > set the position back to where it was initially during the tick, this will not cause the sprite to flicker btw.
I think doing it like this will also resize the image, depending on what you do that´s exactly what you may want.
Load the image forum... Come on