I don't understand well what you're trying to do.
If you need to load images into a blob field in pdox, you have no need to memorize the file name, since you won't be using the file anymore, after the initial insertion.
If you memorize the filename, that would mean that the file name would not change in time, so you should NOT load into a field the image, but instead use the file name to load at runtime the image file in a image control.
Anyhow, if you need to resize the image to show it, you'd better have two versions of the image, one big and one small, rather than resize it every time you need; even if you only need a small version, it's a better idea to resize it before insertion in the db.
You can mass-resize many images by using any of the batch image processing softwares you find on the net: ACDSee, XnView, and many others have such capabilities.
Even with a small fragment of PHP code you can do that fast and simple.