Christian, the PDB extension
can be used for various file formats, including some image formats. Although, the term "image" can mean different things too, such as a visual image or a snapshot of a database or file system.
To the questioner, please clarify what you mean exactly by "PDB image files". Also, would you like to compare the file names, file data, or the internal contents of the database snapshot (if you are in fact talking about a database "image")?
If you just want to compare file names, that's easy. Just get the name of the file you are comparing against and get the names of all the files in another directory and use a for loop to compare those filenames to the primary file name.
The process would be similar if you are comparing file data. Instead of comparing file names, you just load up the file data and compare that instead.
If you would like to compare data inside databases, then you'll want to use some SQL to query the PDB files and extract the data from them. Once you extract the data, you can compare it just as you would the file names or file data.