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Finding peak value in 2d array (image)

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Gregory

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Nov 23, 2009, 10:30:20 AM11/23/09
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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

Carlos Adrian Vargas Aguilera

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Nov 23, 2009, 10:55:19 AM11/23/09
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Check out extrema2.m

http://www.mathworks.com/matlabcentral/fileexchange/12275-extrema-m-extrema2-m

Carlos

Bruno Luong

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Nov 23, 2009, 11:48:05 AM11/23/09
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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

ImageAnalyst

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Nov 23, 2009, 2:53:49 PM11/23/09
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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)));

Bruno Luong

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Nov 23, 2009, 2:59:19 PM11/23/09
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ImageAnalyst <imagea...@mailinator.com> wrote in message <dafe86c7-8e9f-4dc4...@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

Message has been deleted

nate271...@gmail.com

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Jul 24, 2012, 12:41:43 AM7/24/12
to Gregory
On Monday, November 23, 2009 7:30:20 AM UTC-8, Gregory wrote:
> I&#39;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&#39;d like something along the lines of [r,c,p] = findPeak(I).
> I&#39;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&#39;ve not been successful.
> Thanks
try this one,
http://www.mathworks.com/matlabcentral/fileexchange/37388-fast-2d-peak-finder

nate271...@gmail.com

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Jul 24, 2012, 12:40:50 AM7/24/12
to Gregory
On Monday, November 23, 2009 7:30:20 AM UTC-8, Gregory wrote:
> I&#39;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&#39;d like something along the lines of [r,c,p] = findPeak(I).
> I&#39;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&#39;ve not been successful.
> Thanks

you can try this peak finder:
http://www.mathworks.com/matlabcentral/fileexchange/37388-fast-2d-peak-finder
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