55:248 Advanced Image Processing

Spring 2013, Milan Sonka

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Matlab Notes

Here are some useful Matlab image commands:

  • a=imread('pool.tiff');
  • b=imread('shapes2.tiff');
  • info=imfinfo('pool.tiff')
  • info=imfinfo('shapes2.tiff')
  • imshow(a,'truesize')
  • figure
  • imshow(b,'truesize')
  • title('Original Image')
  • c=fft2(b);
  • d=log(1+abs(c));
  • e=mat2gray(d);
  • figure
  • imshow(e,'truesize')
  • title('FFT of original Image')
  • f=fftshift(e);
  • figure
  • imshow(f,'truesize')
  • title('FFT shift')
  • c_inv=ifft2(c);
  • g=real(abs(c_inv));
  • figure
  • imshow(g,'truesize')
  • title('Inverse FFT')
Original Image
FFT of Image
FFT shift

See how the FFT changes if you shrink the image by a factor of 2 in each dimension.

ex.

a=imread('shapes2.tiff');
b=zeros(256);
b(1:128,1:128)=imresize(a,0.5,'nearest');
imshow(b,'truesize')
c=fft2(b);
d=log(1+abs(c));
e=mat2gray(d);
figure
imshow(e,'truesize')
title('FFT of original Image')
f=fftshift(e);
figure
imshow(f,'truesize')
title('FFT shift')