FFT变换去除图像背景纹理

Halcom

代码如下：

1. dev_update_off ()
   
2. dev_set_draw('margin')
   
3. Scale := [1.0,.65]
   
4. MinGray := [55,100]
   
5. * Read and display the image
   
6. read_image (Image, 'C:/Users/ysw/Desktop/2.jpg')
   
7. count_channels(Image, Channels)
   
8. if(Channels>1)
   
9.     rgb1_to_gray(Image, Image)
   
10. endif
    
11. get_image_size (Image, Width, Height)
    
12. dev_set_part (0, 0, Height - 1, Width - 1)
    
13. dev_display (Image)
    
14. *
    
15. * Perform fft and display spectrum
    
16. optimize_fft_speed (Width, Height, 'standard')
    
17. *
    
18. fft_generic (Image, ImageFFT, 'to_freq', -1, 'sqrt', 'dc_center', 'complex')
    
19. dev_set_color ('red')
    
20. dev_display (ImageFFT)
    
21. *
    
22. * Detect the eight most significant peaks in the spectrum
    
23. power_real (ImageFFT, PowerSpectrum)
    
24. binomial_filter (PowerSpectrum, ImageSmooth, 9, 9)
    
25. threshold (ImageSmooth, Region, MinGray[0], 100000)
    
26. connection (Region, ConnectedRegions)
    
27. select_shape (ConnectedRegions, SelectedRegions, 'area', 'and', 3, 200)
    
28. union1 (SelectedRegions, RegionUnion)
    
29. reduce_domain (ImageSmooth, RegionUnion, ImageReduced)
    
30. local_max (ImageReduced, LocalMaxima)
    
31. *
    
32. * Next, detect peaks one octave higher, i.e., at twice
    
33. * the frequency of the most significant peaks
    
34. shape_trans (LocalMaxima, RegionTrans, 'convex')
    
35. * Construct ROI band at twice the frequency
    
36. hom_mat2d_identity (HomMat2DIdentity)
    
37. hom_mat2d_scale (HomMat2DIdentity, 1.5, 1.5, Height / 2, Width / 2, HomMat2DScale)
    
38. affine_trans_region (RegionTrans, RegionTrans1, HomMat2DScale, 'nearest_neighbor')
    
39. hom_mat2d_scale (HomMat2DIdentity, 1.3, 1.3, Height / 2, Width / 2, HomMat2DScale)
    
40. affine_trans_region (RegionTrans, RegionTrans2, HomMat2DScale, 'nearest_neighbor')
    
41. difference (RegionTrans1, RegionTrans2, RegionDifference)
    
42. * Extract the peaks at twice the frequency
    
43. reduce_domain (ImageSmooth, RegionDifference, ImageReduced)
    
44. threshold (ImageReduced, Region, 16, 100000)
    
45. reduce_domain (ImageSmooth, Region, ImageReduced)
    
46. local_max (ImageReduced, LocalMaxima2)
    
47. *
    
48. * Merge the peaks of both octaves and enlarge them to
    
49. * integrate the relevant frequencies into the filter
    
50. union2 (LocalMaxima, LocalMaxima2, RegionUnion)
    
51. dilation_circle (RegionUnion, RegionDilation, 15.5)
    
52. paint_region (RegionDilation, ImageFFT, ImageFFTFiltered, 0, 'fill')
    
53. dev_display (ImageFFT)
    
54. dev_display (RegionDilation)
    
55. *
    
56. * Apply the filter and display the results
    
57. fft_generic (ImageFFTFiltered, ImageFiltered, 'from_freq', 1, 'sqrt', 'dc_center', 'byte')
    
58. sub_image (Image, ImageFiltered, ImageTexture, 1, 128)
    
59. dev_display (ImageTexture)
    

复制代码

（1）关键在于频率成分的选取；规则的纹理，均为低频成分，去掉低频成分即可。
（2）此代码中，关键点在于上、下两个频域成分的去除。

参考链接：https://pan.baidu.com/s/1RpiNyfULyjx7om_ta1LYzQ