Okay, that was not really the way to do this, and you didn't compress your data, you just resized your partitions.
Do you have a backup? Do you have an external HDD you could install Mac OS X onto in case you don't have a backup and need to actually recover files from the internal HDD?
To retrieve files, that have been deleted and also been emptied from the Trash or are on unrecognisable partitions or HDDs, you can use
Data Rescue 3 (
trial lets you scan the HDD and see, if data is recoverable, but to actually recover files, you need to buy the full version for 99 USD) or
FileSalvage (
trial lets you scan the HDD and see, if data is recoverable, but to actually recover files, you need to buy the full version for 89.95 USD).
DiskDrill - lets you recover data from HFS/HFS+, FAT, NTFS & other file systems right on your Mac.
Also know, that you should immediately stop any writing processes to the actual HDD. If it is the same HDD as the one your operating system (OS) resides on, it is better to use an external HDD with Mac OS X on to boot from and install
Data Rescue or
FileSalvage onto to scan the HDD from which the data has been accidentally deleted.