Uploading multi-image tumblr posts.

How does one upload a tumblr post – such as a comic, for instance – that has multiple separate images? I see that sort of short comics from tumblr ask blogs quite often, so obviously a way must exist, but I have no idea what that is: using the “fetch” function on the uploading page only grabs the topmost image.

You have to save the images locally and edit them into one single image manually. I use Inkscape for this, has infinite canvas and snap alignment, but other tools exist.