Discrete cosine transform

[grivet]

Hello,
The discrete cosine transform is often used in image processing and in 
some versions of Fourier transform spectroscopy. Does such a function 
exist in Scilab?  Are there any plans to implement it?
The DCT (and DST, the discrete sine transform) are available in FFTW but 
it would be convenient if they were directly callable in Scilab.
Failing that, doesnanybody have a ready made version of these transforms 
built on fft?
Thanks in advance for your suggestions
JP Grivet