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ROBOTICS Handbook of Computer Vision Algorithms in Image Algebra Part 7

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Tham khảo tài liệu 'robotics handbook of computer vision algorithms in image algebra part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | and b x 3 x fc a f respectively. Alternate Image Algebra Formulation The semithresholded image can also be derived by restricting the source image to those points whose values he in the threshold range and then extending the restriction to X with value 0. The image algebra formulation for this method of semithresholding is b If appropriate instead of constructing a result over X one can construct the subimage c of a containing only those pixels lying in the threshold range that is Comments and Observations Figures 4.3.2 and 4.3.3 below show the thresholded and semithresholded images of the original image of the Thunderbirds in Figure 4.3.1. Figure 4.3.1 Image of Thunderbirds a. Figure 4.3.2 Thresholded image of Thunderbirds b c d 190 a . Figure 4.3.3 Semithresholded image of Thunderbirds b a C d 190 a . 4.4. Multilevel Thresholding Global thresholding and semithresholding techniques Sections 4.2 and 4.3 segment an image based on the assumption that the image contains only two types of regions. Certainly an image may contain more than two types of regions. Multilevel thresholding is an extension of the two earlier thresholding techniques that allows for segmentation of pixels into multiple classes 1 . For example if the image histogram contains three peaks then it is possible to segment the image using two thresholds. These thresholds divide the value set into three nonoverlapping ranges each of which can be associated with a unique value in the resulting image. Methods for determining such threshold values are discussed in Sections 4.6 4.7 and 4.8. Let be the source image and let kỵ . kn be threshold values satisfying fy k2 . kn. These values partition R into n 1 intervals which are associated with values vỵ . v ỵ in the thresholded result image. A typical sequence of result values might be 1 11 0. The thresholded image b c R is defined by Image Algebra Formulation R R Define the function J by The thresholded image can be computed by composing f with a i.e. b .