halcon视觉缺陷检测系列（3）频域和空间域转换的方法详解

*http://www.ihalcon.com/read-13031-1.html
*缺陷检测，将木板的划痕提取出来
dev_update_off ()
dev_close_window ()
read_image (Image, '缺陷检测木板划痕提取.jpg')
*彩色转灰度图
count_channels (Image, Channels)
if (Channels == 3 or Channels == 4)
    rgb1_to_gray (Image, Image)
endif
get_image_size (Image, Width, Height)
dev_open_window_fit_size (0, 0, Width, Height, -1, -1, WindowHandle)
dev_display (Image)
*傅里叶变换去背景
fft_generic (Image, ImageFFT, 'to_freq', -1, 'sqrt', 'dc_center', 'complex')
gen_rectangle2 (Rectangle1, 308.5, 176.56, rad(-0), 179.4, 7.725)
gen_rectangle2 (Rectangle2, 306.955, 175, rad(-90), 180.765, 4.68)
union2 (Rectangle1, Rectangle2, UnionRectangle)
paint_region (UnionRectangle, ImageFFT, ImageResult, 0, 'fill')
fft_generic (ImageResult, ImageFFT1, 'from_freq', 1, 'sqrt', 'dc_center', 'byte')
*提取划痕
threshold (ImageFFT1, Regions, 5, 240)
connection (Regions, ConnectedRegions)
select_shape (ConnectedRegions, SelectedRegions, 'area', 'and', 20, 99999)
union1 (SelectedRegions, RegionUnion)
dilation_rectangle1 (RegionUnion, RegionDilation, 5, 5)
connection (RegionDilation, ConnectedRegions1)
select_shape (ConnectedRegions1, SelectedRegions1, ['width','height'], 'and', [30,15], [150,100])
dilation_rectangle1 (SelectedRegions1, RegionDilation1, 11, 11)
union1 (RegionDilation1, RegionUnion1)
skeleton (RegionUnion1, Skeleton)
*显示
dev_set_color ('red')
dev_display (Image)
dev_display (Skeleton)

detect_indent_fft.hdev
* Optimize the fft speed for the specific image size
optimize_rft_speed (Width, Height, 'standard')
* 
* Construct a suitable filter by combining two gaussian
* filters
Sigma1 := 10.0
Sigma2 := 3.0
gen_gauss_filter (GaussFilter1, Sigma1, Sigma1, 0.0, 'none', 'rft', Width, Height)
gen_gauss_filter (GaussFilter2, Sigma2, Sigma2, 0.0, 'none', 'rft', Width, Height)
sub_image (GaussFilter1, GaussFilter2, Filter, 1, 0)
* 
* Process the images iteratively
NumImages := 11
for Index := 1 to NumImages by 1
    * 
    * Read an image and convert it to gray values
    read_image (Image, 'plastics/plastics_' + Index$'02')
    rgb1_to_gray (Image, Image)
    * Perform the convolution in the frequency domain
    rft_generic (Image, ImageFFT, 'to_freq', 'none', 'complex', Width)
    convol_fft (ImageFFT, Filter, ImageConvol)
    rft_generic (ImageConvol, ImageFiltered, 'from_freq', 'n', 'real', Width)