union_lines

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• This program shows how to detect defects (scratches) in
• an inhomogeneously illuminated surface by filtering in
• the frequency domain.
• First, a suitable bandpass filter is created. Then, the
• input image is fourier transformed and filtered in the
• frequency domain, so that high frequency information is
• enhanced. Finally, it is transformed back to the
• spatial domain and the enhanced defects are post-processed
• by morphology.

• dev_update_off () dev_close_window () read_image (Image, 'surface_scratch') invert_image (Image, ImageInverted) get_image_size (Image, Width, Height) dev_open_window (0, 0, Width, Height, 'black', WindowHandle) set_display_font (WindowHandle, 16, 'mono', 'true', 'false') dev_display (Image)

• Optimize the speed of the fast fourier transform
• Message := 'Optimize the speed of the fast fourier transform.'
• Message[1] := 'Please wait...'
• disp_message (WindowHandle, Message, 'window', 12, 12, 'black', 'true')
• optimize_rft_speed (Width, Height, 'standard')
• disp_continue_message (WindowHandle, 'black', 'true')
• stop ()
• Enhance the scratches by filtering in the frequency domain gen_sin_bandpass (ImageBandpass, 0.4, 'none', 'rft', Width, Height) rft_generic (ImageInverted, ImageFFT, 'to_freq', 'none', 'complex', Width) convol_fft (ImageFFT, ImageBandpass, ImageConvol) rft_generic (ImageConvol, Lines, 'from_freq', 'n', 'byte', Width)
• Segment the scratches by using morphology threshold (Lines, Region, 5, 255) connection (Region, ConnectedRegions) select_shape (ConnectedRegions, SelectedRegions, 'area', 'and', 5, 5000) dilation_circle (SelectedRegions, RegionDilation, 5.5) union1 (RegionDilation, RegionUnion) reduce_domain (Image, RegionUnion, ImageReduced) lines_gauss (ImageReduced, LinesXLD, 0.8, 3, 5, 'dark', 'false', 'bar-shaped', 'false') union_collinear_contours_xld (LinesXLD, UnionContours, 40, 3, 3, 0.2, 'attr_keep') select_shape_xld (UnionContours, SelectedXLD, 'contlength', 'and', 15, 1000) gen_region_contour_xld (SelectedXLD, RegionXLD, 'filled') union1 (RegionXLD, RegionUnion) dilation_circle (RegionUnion, RegionScratches, 10.5)
• Display the results dev_set_draw ('margin') dev_set_line_width (3) dev_set_colored (12) dev_display (Image) dev_display (RegionScratches)

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connection (Region, ConnectedRegions) select_shape (ConnectedRegions, SelectedRegions, 'area', 'and', 5, 5000) dilation_circle (SelectedRegions, RegionDilation, 5.5) union1 (RegionDilation, RegionUnion) reduce_domain (Image, RegionUnion, ImageReduced) lines_gauss (ImageReduced, LinesXLD, 0.8, 3, 5, 'dark', 'false', 'bar-shaped', 'false') union_collinear_contours_xld (LinesXLD, UnionContours, 40, 3, 3, 0.2, 'attr_keep') select_shape_xld (UnionContours, SelectedXLD, 'contlength', 'and', 15, 1000) gen_region_contour_xld (SelectedXLD, RegionXLD, 'filled') union1 (RegionXLD, RegionUnion) dilation_circle (RegionUnion, RegionScratches, 10.5)