Finding peak value in 2d array (image)
in [Matlab]
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From: Gregory on 23 Nov 2009 10:30 I'm new to Matlab... I need to find the peak value stored in a 2d array which is actually an image (640x480). I need to know the row,column, and pixel value of the peak. Ideally I'd like something along the lines of [r,c,p] = findPeak(I). I've been stumbling around trying to find a solution to what I know is probably a trivial problem. I thought max might do the trick, but I've not been successful. Thanks
From: Carlos Adrian Vargas Aguilera on 23 Nov 2009 10:55 Check out extrema2.m http://www.mathworks.com/matlabcentral/fileexchange/12275-extrema-m-extrema2-m Carlos
From: Bruno Luong on 23 Nov 2009 11:48 If you need faster code, you might be interested in using a min/max filter on FEX (mex installation required). z = peaks(500); % on FEX http://www.mathworks.com/matlabcentral/fileexchange/24705 maxz = minmaxfilt(z,[],'max','same'); [i j] = find(maxz==z); % Check surf(z); hold on; zmax = z(sub2ind(size(z),i,j)); plot3(j,i,zmax,'vr','MarkerSize',20); Bruno
From: ImageAnalyst on 23 Nov 2009 14:53 For multiple local 2D max of different values, you can use imregionalmax() if you have the Image Processing Toolbox. For a global max, you can use the find() function like Bruno showed you. Or do something like [rows cols] = find(imageArray == max(max(imageArray)));
From: Bruno Luong on 23 Nov 2009 14:59
ImageAnalyst <imageanalyst(a)mailinator.com> wrote in message <dafe86c7-8e9f-4dc4-9cf4-024694d94012(a)e20g2000vbb.googlegroups.com>... > For a > global max, you can use the find() function like Bruno showed you. Accept that my code looks for all *local* maxima (including a global one). Bruno |