I have a webpage that is presenting multiple images stuck together that appear as a single image (currently, in a table with no borders or gaps between the images). The images come from different sites and change somewhat regularly (I don't have any control over them). I would like the viewers of my site to be able to right click on the image and save it as a single image.

Some additional details/caveats... I'm generating the html from php. Some of the images come from sites that require username/passwords and the user will have to already have logged into those sites so that they're able to view the images. I don't want the users to have to provide me with their username&passwords (they probably don't either), so I don't think having php do the stitching is an option.

As an extra bonus, I'd like the default filename to be generated from my php, so if there's a way to set that, that'd be great.

Thanks.
My php doesn't actually access the image. All my php does is generate the html that has links to the images. When the user views my webpage, they get the links from me and their browser goes and accesses the images - directly from their source (with username and password), not me. Right now, all I provide is the html code.