use imcrop and specify width and height but not starting location?

Is there a way to create a specified size rectangle on an image without a set starting point? So I could move the ROI around on the image and save that chunk but without being able to click an drage to change the size of the rectangle?

Answer 1

[DGM]

This is an attempt to constrain the size of the ROI object during user interaction.

% say you have an image
inpict = imread('peppers.png');

% and you know the box geometry
cropsz = [200 100]; % [x y] (pixels)

% start by displaying the image
figure(1)
imshow(inpict);

% create an ROI object with the specified size
% at some default location (e.g. the image origin)
myROI = drawrectangle(gca,'position',[0 0 cropsz]);
addlistener(myROI,'MovingROI',@(a,b) forcesize(myROI,cropsz));

% the ROI object can be manually dragged around the image
% attempts to resize the object will be prevented

% a simple means to wait for the user
input('Press enter when you''re done moving the ROI object.','s');

% crop using the offsets from the ROI and the specified size
outpict = imcrop(inpict,[myROI.Position(1:2) cropsz]);

% show the result
figure(2)
imshow(outpict)

function forcesize(hObject,fixedsz)
    hObject.Position(3:4) = fixedsz;
end

[r_soo]

Thank you so much this helps a lot!

Answer 2

[Image Analyst]

Maybe try drawrectangle. Demo attached. Adapt as needed.