Re: [WM]: Ooura's mathematical software packages for a fast DCT

[Nicholas Sheppard <nps@uow.edu.au>]

On Tue, 9 Nov 2004, tpj wrote:

> Has anybody used it?  Is it really a fast 2D-DCT? And the inverse 2D-IDCT?

I used it to implement the well-known method of Cox, et al. It appears to work if you follow Ooura's instructions carefully (which
takes some concentration).

> Can explain me how convert a NxN image (or NxM) to an image of n1xn2, 
> where n1=power of 2 and n2=power of 2, without alter too much the 
> image?

I pad it with zeroes out to the next power of two, though the vast majority of the images I use for testing are already in powers of
two.
The results you get with a padded image probably aren't as good as what you get with one that is already the right size, but I don't
know of anything better to do unless you want to use a slow DCT.

Hope this helps.

--
Nicholas Sheppard                                   | Ph: +61 2 4221 3788
Research Fellow                                     | Fax: +61 2 4221 4170
School of Information Technology & Computer Science | E-mail: nps@uow.edu.au
The University of Wollongong, Australia             | WWW: www.uow.edu.au/~nps





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