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fspecial函數
用於建立預定義的濾波運算元，其文法格式為：h = fspecial(type)h = fspecial(type，para)其中type指定運算元的類型，para指定相應的參數；2type的類型有
‘average‘averaging filter為均值濾波，參數為hsize代表模板尺寸，預設值為[3，3]。H = FSPECIAL(‘average‘,HSIZE) returns an averaging filter H of sizeHSIZE. HSIZE can be a vector specifying the number of rows and columns inH or a scalar, in which case H is a square matrix.The default HSIZE is [3 3].‘disk‘circular averaging filter為圓形地區均值濾波，參數為radius代表地區半徑，預設值為5.H = FSPECIAL(‘disk‘,RADIUS) returns a circular averaging filter(pillbox) within the square matrix of side 2*RADIUS+1.The default RADIUS is 5.‘gaussian‘Gaussian lowpass filter為高斯低通濾波，有兩個參數，hsize表示模板尺寸，預設值為[3 3]，sigma為濾波器的標準值，單位為像素，預設值為0.5.H = FSPECIAL(‘gaussian‘,HSIZE,SIGMA) returns a rotationallysymmetric Gaussian lowpass filterof size HSIZE with standarddeviation SIGMA (positive). HSIZE can be a vector specifying thenumber of rows and columns in H or a scalar, in which case H is asquare matrix.The default HSIZE is [3 3], the default SIGMA is 0.5.‘laplacian‘filter approximating the 2-D Laplacian operator為拉普拉斯運算元，參數alpha用於控制運算元形狀，取值範圍為[0，1]，預設值為0.2.H = FSPECIAL(‘laplacian‘,ALPHA) returns a 3-by-3 filterapproximating the shape of the two-dimensional Laplacianoperator. The parameter ALPHA controls the shape of theLaplacian and must be in the range 0.0 to 1.0.The default ALPHA is 0.2.‘log‘Laplacian of Gaussian filter為拉普拉斯高斯運算元，有兩個參數，hsize表示模板尺寸，預設值為[3 3]，sigma為濾波器的標準差，單位為像素，預設值為0.5.H = FSPECIAL(‘log‘,HSIZE,SIGMA) returns a rotationally symmetricLaplacian of Gaussian filter of size HSIZE with standard deviationSIGMA (positive). HSIZE can be a vector specifying the number of rowsand columns in H or a scalar, in which case H is a square matrix.The default HSIZE is [5 5], the default SIGMA is 0.5.‘motion‘motion filter為移動模糊運算元，有兩個參數，表示攝像物體逆時針方向以theta角度運動了len個像素，len的預設值為9，theta的預設值為0；H = FSPECIAL(‘motion‘,LEN,THETA) returns a filter to approximate, onceconvolved with an image, the linear motion of a camera by LEN pixels,with an angle of THETA degrees in a counter-clockwise direction. Thefilter becomes a vector for horizontal and vertical motions.Thedefault LEN is 9, the default THETA is 0, which corresponds to ahorizontal motion of 9 pixels.‘prewitt‘Prewitt horizontal edge-emphasizing filter用於邊緣增強，大小為[3 3]，無參數H = FSPECIAL(‘prewitt‘) returns 3-by-3 filter that emphasizeshorizontal edges by approximating a vertical gradient. If you need toemphasize vertical edges, transpose the filter H: H‘.[1 1 1;0 0 0;-1 -1 -1].‘sobel‘Sobel horizontal edge-emphasizing filter用於邊緣提取，無參數H = FSPECIAL(‘sobel‘) returns 3-by-3 filter that emphasizeshorizontal edges utilizing the smoothing effect by approximating avertical gradient. If you need to emphasize vertical edges, transposethe filter H: H‘.[1 2 1;0 0 0;-1 -2 -1].‘unsharp‘unsharp contrast enhancement filter為對比增強濾波器。參數alpha用於控制濾波器的形狀，範圍為[0，1]，預設值為0.2
