tailieunhanh - Woven Fabric Engineering Part 9

Tham khảo tài liệu 'woven fabric engineering part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Detection of Defects in Fabric by Morphological Image Processing 223 Fig. 1. Test fabrics with defects row 1 thresholded images row 2 and results of defect detection by morphological erosion row 3 and opening operations row 4 . filtered image when the pixels are converted to either 1 or 0 if it is above or below a preselected threshold value Pth. Therefore Fb 1 if Ffs Pth and Fb 0 if Fsf Pth. The threshold value Pth is however depended on the type of fabric. The test results of morphological operations after the removal of grating structures of fine medium and coarse fabric are shown in Fig. 2. Some general conclusions can be drawn from the results. It is not possible to remove the grating structure of warp and weft yarns by digital spatial filterig particularly for coarse fabric when the size of defects are comparable or slightly bigger than the yarn diameter row 2 of fig. 2 . In fine and medium fabrics it is possible to remove the interlaces grating completely by suitably selecting the diameter of spatial filter and the threshold value. For defect detection opening dilation erosion and closing operations are performed. The type of morphological operations to be performed depends on the types of defects present in the test fabric. The result follows the expected 224 Woven Fabric Engineering pattern for long defects since the connectivity of the yarn in the whole image set is higher than that of the defects. In fig. 2 for the detection of defect present in the first type of test fabric opening operations are carried out. For defects in the second third and fourth types dialtion erosion and opening operations are carried out respectively. 4. Morphological filtering operations for noise removal from fabric image Before applying the morphological operations for the detection of defects in woven fabric the gray fabric image F is de-noised by using morphological filtering technique. This preprocessing is necessary particularly for cotton fabric where the presence of .