Moving ROIs within images and across images
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Nandini Chatterjee
le 11 Nov 2020
Commenté : Auwal
le 16 Oct 2023
I have a code where I read in two images and display it side-by-side. I draw a region of interest within the first image, and the region is automatically shown on the second image. When I move the rectangle to another region within the first image, only that rectangle moves (not the second image's rectangle). How can I fix this so that when I move the first rectangle, the second move moves to the same position as well.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/410205/image.png)
What I have now
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/410210/image.png)
% Read images
I = imread('cameraman.tif');
I2 = imread('cameraman.tif');
% plot image 1 & draw a rectangular ROI on images
subplot(1,2,1); imshow(I);
roi = drawrectangle('LineWidth',2,'Color','white');
subplot(1,2,2); imshow(I2);
roi2 = drawrectangle(gca,'Position',roi.Position);
% set up listeners for ROI moving events
addlistener(roi,'MovingROI',@allevents);
addlistener(roi,'ROIMoved',@allevents);
% allevents callback function displays the previous position & the current position of the ROI
function allevents(~,evt)
evname = evt.EventName;
switch(evname)
case{'MovingROI'}
disp(['ROI moving previous position: ' mat2str(evt.PreviousPosition)]);
disp(['ROI moving current position: ' mat2str(evt.CurrentPosition)]);
case{'ROIMoved'}
disp(['ROI moved previous position: ' mat2str(evt.PreviousPosition)]);
disp(['ROI moved current position: ' mat2str(evt.CurrentPosition)]);
end
end
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Réponse acceptée
Ameer Hamza
le 11 Nov 2020
Modifié(e) : Ameer Hamza
le 11 Nov 2020
Currently, your event lister function is just priting the values. You need to set the position too. Try following code
% Read images
I = imread('cameraman.tif');
I2 = imread('cameraman.tif');
% plot image 1 & draw a rectangular ROI on images
subplot(1,2,1); imshow(I);
roi = drawrectangle('LineWidth',2,'Color','white');
subplot(1,2,2); imshow(I2);
roi2 = drawrectangle(gca,'Position',roi.Position);
% set up listeners for ROI moving events
addlistener(roi,'MovingROI',@(r1,evt) allevents(r1,evt,roi2));
addlistener(roi,'ROIMoved',@(r1,evt) allevents(r1,evt,roi2));
% allevents callback function displays the previous position & the current position of the ROI
function allevents(roi1,evt,roi2)
evname = evt.EventName;
roi2.Position = roi1.Position;
switch(evname)
case{'MovingROI'}
disp(['ROI moving previous position: ' mat2str(evt.PreviousPosition)]);
disp(['ROI moving current position: ' mat2str(evt.CurrentPosition)]);
case{'ROIMoved'}
disp(['ROI moved previous position: ' mat2str(evt.PreviousPosition)]);
disp(['ROI moved current position: ' mat2str(evt.CurrentPosition)]);
end
end
Or a simpler solution using linkprop()
% Read images
I = imread('cameraman.tif');
I2 = imread('cameraman.tif');
% plot image 1 & draw a rectangular ROI on images
subplot(1,2,1); imshow(I);
roi = drawrectangle('LineWidth',2,'Color','white');
subplot(1,2,2); imshow(I2);
roi2 = drawrectangle(gca,'Position',roi.Position);
linkprop([roi, roi2], 'Position')
15 commentaires
Ameer Hamza
le 21 Nov 2020
Try this definition of event callback function
function allevents(roi,~,I,I2,I3,ax1,ax2,ax3)
rect = roi.Position;
ax1.Children.CData = imcrop(I, rect); axis(ax1, 'auto');
ax2.Children.CData = imcrop(I2, rect); axis(ax2, 'auto');
ax3.Children.CData = imcrop(I3, rect); axis(ax3, 'auto');
end
Plus de réponses (1)
Auwal
le 16 Oct 2023
Thanks everyone that contributed.
please may i know if it is possible to get the pixel values in the defined roi and calculate the mean value.
Thanks in advace
2 commentaires
Image Analyst
le 16 Oct 2023
Yes
croppedImage = imcrop(originalImage, roi.Position); % Get values in the rectangle.
meanValue = mean2(croppedImage)
Auwal
le 16 Oct 2023
Thanks so much Image Analyst. It works fine.
However, I am not sure why is not working with circular roi "drawcircle"
Many thanks
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