1. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

2. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

3. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

4. MATLAB/Image Processing Toolbox
MATLAB Fourier transforms
>> f=imread(‘Figure_Rectangle.jpg’); % load in spatial rectangle
>> F=fft2(f); % do 2D FFT
>> S=abs(F); % determine magnitude for display
>> imshow(S, [ ]) % shows in four corners of display
>> Fc=fftshift(F); % shift FFT to center
>> imshow(abs(Fc), [ ]); % show magnitude of FFT in center
% much tougher to do display transform
>> g=im2unit8(mat2gray(log(1+double(f))));
>> imshow(g)
% double converts the image to double precision floating point
% mat2gray brings the values to the range [0,1]
% im2unit8 brings the values back to the range [0,255]
% general log transform
>> g=im2unit8(mat2gray(c*log(1+double(f))));
SEE GWE, Section 4.2 Computing and Visualizing the 2-D DFT in MATLAB
GWE, Section Logarithmic and Contrast Stretching Transformations

5. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

6. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

7. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

8. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

9. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

10. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

11. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

12. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

13. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

14. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

15. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

16. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

17. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

18. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

19. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

20. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

21. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

22. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

23. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

24. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

25. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

26. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

27. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

28. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

29. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

30. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

31. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

32. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

33. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

34. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

35. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

36. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

37. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

38. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

39. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

40. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

41. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

42. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

43. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

44. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain

45. Image Enhancement in the
Chapter 4
Image Enhancement in the
Frequency Domain