Re: {JPEG}Discrete Cosine Transformation

From: Gernot Hoffmann (
Date: 07/12/04

Date: 12 Jul 2004 09:10:49 -0700 (Minti) wrote in message news:<>...
> Hi there,
> I am doing some research on JPEG, being from a non-mathematical
> background I am having quite some difficulty in understanding the
> basic concepts of DCT. I have searched the web for couple of days but
> nothing concrete. A lot of articles just refered to Rao's book for
> understanding DCT, unfortunately I can't find it anywhere nearby. I
> will be thankful if anyone could either explain the _basis_ and
> _advantages_ of DCT or provide some pointers on web, pointers to
> articles on ACM also welcomed.
> Thanks.


in at least one of the URLs in the other posts the DCT is considered
as the cosine part of the discrete Fourier series. Thatīs wrong.
The cosines in the DCT have a phase shift.
Some illustrations are here:
The graphics may help to understand the SHAPES of the functions in the
function system.

Best regards --Gernot Hoffmann