Asked by ganesh s
on 21 Sep 2011

please tell me how to find and plot the magnitude of the image & how to quantize the output after finding it's magnitude

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Answer by Walter Roberson
on 21 Sep 2011

Accepted answer

Finding the magnitude of the discrete Fourier transform does **not** calculate the magnitude of the image: it only finds the magnitude of the frequency components. If you were to quantize the frequency components and then ifft() to get back to an image, I suspect the result would be pretty messy.

ganesh s
on 23 Sep 2011

@ walter Roberson :thanks sir

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## 3 Comments

## Image Analyst (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/16352-how-to-find-magnitude-of-image-of-size-256x384#comment_36106

I've been doing imaging over 30 years and I have no idea what this means.

## ganesh s (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/16352-how-to-find-magnitude-of-image-of-size-256x384#comment_36148

sir, i have taken the color image of size 256x384. then i have converted it in to gray image (using rgb2gray).then i have find it's Fourier transform.then i need to find the magnitude of the image(because after finding FFT of image we get the complex values)for the image quantization.

I know how to find the magnitude of image(using abs command)but i don't know how to do image quantization on the basis of magnitude values of image (because it's contain exponential values ) & i want to know how to quantize the gray image

## Image Analyst (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/16352-how-to-find-magnitude-of-image-of-size-256x384#comment_36583

I still have no idea what you said. The gray scale image is already quantized. Do you want to quantize it in intensity differently? Like into fewer gray levels?