Matlab 的fspecial函数用法

fspecial 函数用于建立预定义的滤波算子，其语法格式为： h = fspecial(type) h = fspecial(type ， para) 其中 type 指定算子的类型， para 指定相应的参数； type 的类型有： 1 、 'average'averaging filter 为均值滤波，参数为 hsize 代表模板尺寸，默认值为【 3 ， 3 】。 H = FSPECIAL('average',HSIZE) returns an averaging filter H of size HSIZE. HSIZE can be a vector specifying the number of rows and columns in H or a scalar, in which case H is a square matrix. The default HSIZE is [3 3]. 2 、 'disk'circular averaging filter 为圆形区域均值滤波，参数为 radius 代表区域半径，默认值为 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. 3 、 'gaussian'Gaussian lowpass filter 为高斯低通滤波，有两个参数， hsize 表示模板尺寸，默认值为【 3 3 】， sigma 为滤波器的标准值，单位为像素，默认值为 0.5. H = FSPECIAL('gaussian',HSIZE,SIGMA) returns a rotationally symmetric Gaussian lowpass filterof size HSIZE with standard deviation SIGMA (positive). HSIZE can be a vector specifying the number of rows and columns in H or a scalar, in which case H is a square matrix. The default HSIZE is [3 3], the default SIGMA is 0.5. 4 、 'laplacian' filter approximating the 2-D Laplacian operator 为拉普拉斯算子，参数 alpha 用于控制算子形状，取值范围为【 0 ， 1 】，默认值为 0.2. H = FSPECIAL('laplacian',ALPHA) returns a 3-by-3 filter approximating the shape of the two-dimensional Laplacian operator. The parameter ALPHA controls the shape of the Laplacian and must be in the range 0.0 to 1.0. The default ALPHA is 0.2. 5 、 'log'Laplacian of Gaussian filter 为拉普拉斯高斯算子，有两个参数， hsize 表示模板尺寸，默认值为【 3 3 】， sigma 为滤波器的标准差，单位为像素，默认值为 0.5. H = FSPECIAL('log',HSIZE,SIGMA) returns a rotationally symmetric Laplacian of Gaussian filter of size HSIZE with standard deviation SIGMA (positive). HSIZE can be a vector specifying the number of rows and 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. 6 、 'motion'motion filter 为运动模糊算子，有两个参数，表示摄像物体逆时针方向以 theta 角度运动了 len 个像素， len 的默认值为 9 ， theta 的默认值为 0 ； H = FSPECIAL('motion',LEN,THETA) returns a filter to approximate, once convolved with an image, the linear motion of a camera by LEN pixels, with an angle of THETA degrees in a counter-clockwise direction. The filter becomes a vector for horizontal and vertical motions.The default LEN is 9, the default THETA is 0, which corresponds to a horizontal motion of 9 pixels. 7 、 'prewitt'Prewitt horizontal edge-emphasizing filter 用于边缘增强，大小为【 3 3 】，无参数 H = FSPECIAL('prewitt') returns 3-by-3 filter that emphasizes horizontal edges by approximating a vertical gradient. If you need to emphasize vertical edges, transpose the filter H: H'. [1 1 1;0 0 0;-1 -1 -1]. 8 、 'sobel'Sobel horizontal edge-emphasizing filter 用于边缘提取，无参数 H = FSPECIAL('sobel') returns 3-by-3 filter that emphasizes horizontal edges utilizing the smoothing effect by approximating a vertical gradient. If you need to emphasize vertical edges, transpose the filter H: H'. [1 2 1;0 0 0;-1 -2 -1]. 9 、 'unsharp'unsharp contrast enhancement filter 为对比度增强滤波器。参数 alpha 用于控制滤波器的形状，范围为【 0 ， 1 】，默认值为 0.2. H = FSPECIAL('unsharp',ALPHA) returns a 3-by-3 unsharp contrast enhancement filter. FSPECIAL creates the unsharp filter from the negative of the Laplacian filter with parameter ALPHA. ALPHA controls the shape of the Laplacian and must be in the range 0.0 to 1.0. The default ALPHA is 0.2