Topic: Thumbnail generation

I'm curious to learn how SimpleViewer can generate thumbnails out of the images subdirectory rather than the additional thumbnails subdirectory. My objective is to limit the impact on the server, so I'm looking for a way to have my thumbnails and large picture derive from the same file.

I'm currently using the PHP variety of SimpleViewer with no real code variations.

How do I have this cake and eat it too? Thanks in advance!