resave a jpg with same compression

[Guest]

hi i have made a program that modifies jpgs. the problem is when i resave
the new jpg, the compression ratio has changed. i need a way to read the
compression ratio and save it back with the same ratio. do you think this
will keep recompressing the data ?

Thanks,
Daniel

 

[Guest]

hi i have made a program that modifies jpgs. the problem is when i
resave the new jpg, the compression ratio has changed. i need a way
to read the compression ratio and save it back with the same ratio.
do you think this will keep recompressing the data ?

Yes, each time you save a JPEG, it will be recompressed. Also note that the
ratio is abitrarily defined by the JPEG algorithm (i.e. Max Quality in one
implementation is not the same as Max Quality in another).


However, certain operations can be lossless - like cropping or rotation.