Fourier transform code.

Question

Can you help me find a FDCT program to determine the coefficients for a 16x16( JPEG image Bock)?

I will appreciate that.
Thanks,

MetalDwarf · Answer

You will find easily some lessons about the FFT (fast fourier transform) on google. The algorithm is very simple (about 30-40 lines in C for the recursive version, more for the iterative one.
But the problem is that I don t know if the JPEG algorithm uses the FFT itself or a variant of the FFT.

You should try to find a good description of the JPEG algorithm first.
I have a lesson on FFT but it is in french, I don t know if it can help you...

plus_plus_fab · Answer

jpeg doesn't use FFT but DCT (discret cosinus transformation), F for Fast ?

MetalDwarf · Answer

It almost the same algorithm as far as I remember. It transforms the values related to pixels in coefficients of a Fourier decomposition (I apologize for my dirty english, but I don t know the right words in english....). The Fourier transform can indeed be written in 2 forms, one with cosinus and sinus and one with cosinus and phi, (cos(n*w + phi)).
I think that the DCT may be the FFT written in the second form....

There is an other problem I think. Do you know that the pixels are not given to the DCT in RGB? There are turned into an other form, with two values, calles "luminance" and "chrominance" in French (the lumineance deals with light intensity and chrominance with the color).
I don t know exactly how to convert pixels to RGB but you should search something about it too.

You should also take a look at http://www.ijg.org/files/ , which is the official website of the JPEG consortium.

Kenoly_1212 · Answer

Merci, beaucoup pour imediate reponse, Oui je parle et comprend aussi le Francais vous pourvez m'envoyez  les informations en Francais si vous les avez.

ofifi · Answer

svp je cherche le code de la transformée de fourier discrète en c++
merci d'avance.

Fourier transform code.

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