Embodiments include systems and methods for pre-processing and post-processing original and new versions of files as part of difference file generation between the original and new file versions. The systems and methods of an embodiment include a set of algorithms that reduce the difference file size by preprocessing a variety of regions in software images for embedded computing devices, an example of which is the compressed read-only memory (ROM) file system (CRAMFS) image. The algorithms treat a variety of types of data regions that are created by the compiler. Embodiments operate on the server side and the client side. On the server side, the preprocessing generates Compact Functional Differences (CFD) hint data directly from a pair of CRAMFS images, without the use of symbol files or log files generated by compiler/linker utilities.