Re: JPEG compression only retains magnitude information? How about phase information?

Thomas Richter <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> Hi,
> 
> > I guess phase information is not useful at all, so JPEG just ignore them...
> 
> Not quite. A transform I would "ignore" information in case some information
> is definitely lost. Lost in the sense that for a transform "I" there is
> no inverse transformation "I^{-1}". Since DCT is completely reversible, not
> a single bit of information is lost, and thus no kind of "phase" is lost 
> either. Information gets lots only because a) you quantize and b) DCT is
                          ^^^^^^
Hence the two categories of compression method: lotsy  and lossy ;-)

Jon C.