武汉理工大学数字图像处理英文课件 Chapter6（7）.pptVIP

MinMax Neighborhood Filters Example Matlab Function ordfilt Example maxfilt Minfilt Example minfilt Grayscale Image Example (rep=1) Grayscale Image Example (rep=2) Comparison to Laplacian Color Image Example Matlab Function imdiff * A minmax neighborhood filter finds the minimum (maximum) pixel in 3 x 3 neighborhoods of each pixel. Repeated calls to the filter extend the size of the neighborhood. function out = maxfilt(in,repeat) % MAXFILT % out = maxfilt(in); % returns maximum value in a 3 x 3 neighborhood % % out = maxfilt(in,n) repeats the operation n times % % Author: John S. Loomis (17 March 2000) if nargin2 repeat=1; end sp = size(in); sm = sp-1; out = in; for k=1:repeat out(1:sm(1),:) = max(out(1:sm(1),:),out(2:sp(1),:)); out(2:sp(1),:) = max(out(1:sm(1),:),out(2:sp(1),:)); out(:,1:sm(2)) = max(out(:,1:sm(2)),out(:,2:sp(2))); out(:,2:sp(2)) = max(out(:,1:sm(2)),out(:,2:sp(2))); end As a simple example, consider the case of isolated pixels on a zero background: ? a = zeros(9); ? idx = [1 5 9]; ? a(idx,idx) = 1 a = 1 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 1 ? a href=maxfilt.m.htmlmaxfilt/a(a) ans = 1 1 0 1 1 1 0 1 1 1 1 0 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 1 1 0 1 1 1 0 1 1 1 1 0 1 1 1 0 1 1 1 1 0 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 1 1 0