Background: I am trying to use WordPress to resize images uploaded by my users. They are not very savvy when it comes to sizing images before uploading. WP does a fantastic job of reducing the image sizes. My issue is that I would like to use any of the myriad of lightbox-type plugins that require a link to the original file to fire. Often the images that get uploaded are SO big that they consume the entire screen four times over when viewed in a lightbox-type environment. Some of the plugins will artificially re-size the images, but this is done on the fly and still requires a long download time.
Problem: I would like to know if there is a way to make the "File URL" button or the "Link to Image" button (found when adding images to posts) function in a way that provides a link to the "medium" (or any other size) image instead of the original file. I would also like to do the same for the automatically generated image gallery in WP. That is, I'd like [gallery link="file"] to actually link the thumbnails to the "medium" sized images.
I would like to avoid altering core files, but I am not totally against it if there aren't any hooks that can be used instead.
Any thoughts? Thanks!