Kenoly_1212
Messages postés2Date d'inscriptionsamedi 11 décembre 2004StatutMembreDernière intervention12 décembre 2004
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12 déc. 2004 à 03:50
ofifi
Messages postés1Date d'inscriptionjeudi 10 mai 2007StatutMembreDernière intervention27 mai 2008
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27 mai 2008 à 10:10
Can you help me find a FDCT program to determine the coefficients for a 16x16( JPEG image Bock)?
MetalDwarf
Messages postés241Date d'inscriptionmardi 29 octobre 2002StatutMembreDernière intervention23 janvier 2006 12 déc. 2004 à 15:53
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...
MetalDwarf
Messages postés241Date d'inscriptionmardi 29 octobre 2002StatutMembreDernière intervention23 janvier 2006 12 déc. 2004 à 19:56
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
Messages postés2Date d'inscriptionsamedi 11 décembre 2004StatutMembreDernière intervention12 décembre 2004 12 déc. 2004 à 20:54
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.
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