How to fix ROI size irrespective of image

I have multiple images and I am using imcrop function to take ROI in image. The problem with imcrop is it gives me different size of ROI on each image. I would like to take ROI of same size for each image. There is a option in imcrop by which I can select size but for that I need to keep my location of ROI fix. I want to fix window size but vary location of window on image. Is there a function available for this functionality in Matlab?

Answer 1

[Image Analyst]

If you don't need to interactively size it, then just hard code the values and use normal, regular indexing:

row1 = 100; % or whatever.
col1 = 200; % or whatever.
row2 = 150; % or whatever.
col2 = 225; % or whatever.
croppedImage = grayImage(row1:row2, col1:col2);

[Kirti]

I would like to interactively select desired ROI. The problem is , the desired ROI is available at different location on each image. User should be able to select it but the size of selected ROI should be same on all images.

[Image Analyst]

Use ginput to let the user select the upper left corner. Otherwise you can use the mousemove callback to interactively let the user drag a rectangle of fixed size around the image and then fix it whenever they click, but that's more complicated than just using ginput(), though it's more elegant and user friendly.

[Kirti]

Thanks. I am trying to understand how ginput will give me fix size ROI? I am getting coordinates by ginput. And ROI coordinates will vary image to image. Can you please let me know if I have to use any other parameters of ginput to get fix ROI?

[Image Analyst]

You know the size, so you simply add it to the coordinates.

[col1, row1] = ginput(1);
row2 = row1 + height;  % You know the height because you fixed it.
col2 = col1 + width;  % You know the width because you fixed it.