Getting the maximum value of several matrices loaded from image files.

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I have troubles with the max command applied to images files.
I have N=108 image files tif. Each file corresponds to a matrix. I need to load all the matrix/images and compute a matrix containing the maximum values among the 108 matrices.
My script to read the N=108 files is as follows:
imagelist = dir('*.tif');
N = numel(imagelist);
imdata = cell(1, numel(imagelist));
for k = 1: N
imdata{k} = imread(imagelist(k).name);
I don’t know to compute the “maximum matrix” since imdata contains matrices as cells.
indeed I obtain a row vector containing only the maximum values of the first cell.

Accepted Answer

Image Analyst
Image Analyst on 12 Nov 2013
Edited: Image Analyst on 12 Nov 2013
Something like this (untested):
maxImage = zeros(rows, columns, 'uint8');
overallMax = -inf;
for k = 1: N
thisImage = imread(imagelist(k).name);
% Get max of this image.
thisMax = max(thisImage(:));
if thisMax > overallMax
overallMax = thisMax;
% Get max image, in case you really meant that. Delete if not.
maxImage = max(maxImage, thisImage);
Of course you need to make sure that the dimensions (rows, columns, number of color channels) of all the images match up.
Image Analyst
Image Analyst on 15 Nov 2013
OK good. MATLAB has a rule that integers must be combined with integers of the same class. Usually that comes into play when you're adding or multiplying them but I guess you found out that it also applies when you use the max function. There's no such rule for floating point numbers. Anyway, I'm glad you got it working and accepted the answer.

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More Answers (1)

Doug Hull
Doug Hull on 12 Nov 2013
Do not store the images in cells. Just load each in turn, get the maximum value. Compare this maximum value to the previously found maximum value. Keep the maximum of those two. Repeat until all have been done.
  1 Comment
Chiara on 13 Nov 2013
Thanks for your answer. I cannot convert the cells into matrices though. I’ve tried to automatically upload the 108 tif files I have, using strcat function but doesn’t work. My files are “200301_monthly_adg_443_gsm_P90.tif” The only part varying is the first “200301”. I have already implemented strcat function but not with images.

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