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COMPUTER-AIDED INTELLIGENT RECOGNITION TECHNIQUES AND APPLICATIONS phần 4

để đảm bảo rằng các mục được chọn nằm trong các cạnh lớp học, thử nghiệm nó sẽ tự động bằng cách phân loại k-NN. Phương pháp (4) là k có nghĩa là phân nhóm [23], cũng được sử dụng rộng rãi cho LVQ khởi tạo [28,29] và có được nguyên mẫu bằng cách phân cụm dữ liệu huấn luyện của mỗi lớp | Feature Extraction 135 2.3 Step 3 Wavelet-based Segmentation In the previous step the border pixels of hand shape are sequentially traced and represented by a set of coordinates xỂ yỂ i 1 2 . . . .In this step the wavelet-based segmentation technique is adopted to find the locations of five fingertips and four finger roots. As we know these points are located at the corners of the hand shape. Since the crucial corner points Pa Pb and P3 see Figure 9.2 c determine the ROI location in the palm table it is very important to explicitly locate the corner points of the hand shape. The wavelet transform can provide stable and effective segmented results in corner detection. The detected corner points in Figure 9.2 b are illustrated in Figure 9.2 c . 2.4 Step 4 Region Of Interest ROI Generation In this step we will find the Region Of Interest ROI in the palm table. Based on the result generated in Step 3 the location of the ROI is determined from points Pa Pb P3 and geometrical formulae. Thus the square region P P P P of size 256 by 256 is defined to be the region of interest as shown in Figure 9.2 c . From these four points the image of the ROI is cut from the hand image as shown in Figure 9.2 d . 3. Feature Extraction Feature extraction is a step to extract the meaningful features from the segmented ROI for the later modeling or verification process. In extracting the features we use the operator-based approach to extract the line-like features of palm-prints in the ROI of the palm table. First we employ simple Sobel operators to extract the feature points of a palmprint. Four directional Sobel operators S0 S90 S45 and S135 are designed. Consider a pixel of the ROI in the palm table four directional Sobel operators are performed to select the maximal value as the resultant value of the ROI. This operation is carried out according to the following expression f S max f S0 f S90 f S 5 f S135 9.1 Here symbol is defined as the convolution operation. The Sobel features of the