Compressed vs uncompressed study


I have a study that J2K lossless compressed on dcm4chee.
Now I can view it on ohif viewer.
I know compressing studies is a good point for storage and transfer via network.

My question is:

  1. Ohif load image performance: an uncompressed study and J2K lossless compressed of that study. What is better?
    (Compressed study must be uncompressed when it is displayed to the viewport. is it right? So has it affected performance?)

  2. How can I download a compressed study from OHIF?
    I tried to download it by calling dicomWebClient.retrieveStudy(a compressed studyInstanceUID). However, the downloaded result is uncompressed versions of data. What is wrong?