AES, format preserving encryption

i am using cipher-mode 'CTR' for file encryption 
with this mode plain-text and cipher text becomes same size with no-padding 
and even string less than 16 byte(128bit) can be encrypted 
say 5 byte string can be encrypted as 5 byte 
thanks for chilkat!! .

so with encrypt, same length problem is solved 
but still lack of format preserving .

is there any way for format preserving encryption ? 
or FFX-AES supported in latest chilkat encryption module ?