By the way, I've found through experience that just comparing the file size of 2 images is sufficient 99.999% of the time which is good enough for me and is an EXTREMELY light way of doing this. Disclaimer: In my implementation I'm just trying to determine if a new image being added is already there (maybe 20 images max attached to this item). If I was trying to determine if a file already existed in a list of thousands of images, then this method probably wouldn't work as well.

** Get File Size of the Image
lcCompatible=SET("Compatible")
SET COMPATIBLE ON
TRY
  lnFileSize=FSIZE(lcImageFilenameWithPath)
CATCH
  lnFileSize=0
ENDTRY
SET COMPATIBLE &lcCompatible