# imshow, imcrop and imread to set a predefined coordinate system to analyze images

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Hello,
I have a code shown below that analyzes images to quantify a predefined value termed CTR (basically how bright something is against a background)... I want to set a predefined coordinate system instead of always having to select the area to analyze in each image when I have +50 images. I was wondering what I would need to do to make this adjustment and if anyone had any advice on how to do this.
The code is seen below:
close all clear all
%Images should be labled X.jpg, where X is an integer from 1 to Npics. %Enter number of images to be analyzed.
Npics = 46;
pic = [1:1:Npics]; for n = 1:1:Npics
G = rgb2gray(I);
figure(1),imshow(G),title(['Press enter to crop TISSUE section ',num2str(n)]);
pause;
GT = imcrop(G);
M = mean(mean(GT));
figure(1),imshow(G),title(['Press enter to crop CONTRAST section ',num2str(n)]);
pause;
GC = imcrop(G);
C = mean(mean(GC));
mat(n,1) = M;
mat(n,2) = C;
for k = size(mat,1)
CTR(k) = 20.*log10(mat(k,2)./mat(k,1));
end
end
close all

Jean-Marie Sainthillier on 20 Oct 2016
Edited: Jean-Marie Sainthillier on 20 Oct 2016
For the first image use :
[GT,rec] = imcrop(G);
(rec is a 4-element vector with the form [XMIN YMIN WIDTH HEIGHT])
For others images, you can re-use directly (non-interactively) theses coordinates with :
GC = imcrop(G,rec);