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From: Nor Aznim on 5 Jan 2010 09:55
can you help me on jpeg steganography by using DFT instead of DCT? i am having a problem in matlab command in splitting the image into 8x8 blocks, apply DFT to the image, quantization process or encoding process and also the huffman encoding. anyone can help me?
From: Dave Robinson on 5 Jan 2010 11:08
"Nor Aznim" <chempaka_darwish(a)yahoo.com> wrote in message <hhvjsn$faq$1(a)fred.mathworks.com>...
> can you help me on jpeg steganography by using DFT instead of DCT? i am having a problem in matlab command in splitting the image into 8x8 blocks, apply DFT to the image, quantization process or encoding process and also the huffman encoding. anyone can help me?

Have you checked out the function in the image processing toolbox called "blkproc" I seem to remember that this has been designed to help generate the base mechanism for processing images in little blocks with a custom function. I am being a bit vague here as I don't have the Image Processing toolbox on this machine.

Try typing

help blkproc

at your command prompt.

Hope that helps

Dave Robinson
From: Nor Aznim on 27 Jan 2010 10:47
thank you very much! i've done splitting my image to 8x8 blocks using command blkproc. there's another problem that i have. i applied fft on my image and try to get the coefficient. but the coefficient seems to be in imaginary value. what should i do to get real value? this is because i want to do encode process where the value of coefficient must be divide by value in quantizer table before rounding the number to 0 or 1. i think there must be difficult if it is in imaginary number, am i right?
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