武汉理工大学数字图像处理英文课件 Chapter5（1）.pptVIP

Example Filter Convolution Sum Example of Convolution Operation Example Calculation Matlab Function imfilter Filter Example * 1 2 1 2 4 2 1 2 1 1 16 Neighborhood processing often involves mask operations. A mask array, such as shown on the left. identifies coefficients to be associated with a central pixel and its neighbors. Other names for the mask array include template, stencil, and filter. x x x x x x z1 x z7 z4 x z2 x z8 z5 x z3 x z9 z6 x x x x x The mask, shown on the left, is centered at the pixel z5 shown on the right. Pixels marked x do not take part in the operation The pixel z5 in the output image is set to the sum of the products of the elements of the mask and their associated pixels in the input image. The mask is then shifted by one pixel and the process is repeated row by row until the entire new image has been generated. This process is a called a convolution. Input array Output array 1 2 1 2 4 2 1 2 1 1 16 mask 2?16 1?16 4?16 2?16 1 16 mask 1 2 1 2 4 2 1 2 1 1 16 product B = imfilter(A,H) filters the multidimensional array A with the multidimensional filter H. The array, A, can be a nonsparse numeric array of any class and dimension. The result, B, has the same size and class as A. Each element of the output, B, is computed using double-precision floating point. If A is an integer array, then output elements that exceed the range of the integer type are truncated, and fractional values are rounded. B = imfilter(A,H,option1,option2,...) performs multidimensional filtering according to the specified options. rgb = imread(flowers.tif); rgb = im2double(rgb); h = fspecial(motion,50,40); out = imfilter(rgb,h); *