Question about how to use drawline to record line segment lengths in real time

When drawing line on an image, I may need to adjust multiple times to get the optimal position. The drawline example code provided by Matlab can record the line segment length in real time, but I am unable to output and save this real-time length as a variable. I am looking for a way that can tell me the real-time line segment length in the command window as I adjust the line segment, and after I confirm the final position, exit drawline, the function will output the final length value and save it as a variable in the workspace.

Thanks for the help! This is part of my code

img = imread('3.png');
imshow(img);

roi = drawline('Color','r');
addlistener(roi,'MovingROI',@allevents);
addlistener(roi,'ROIMoved',@allevents);

function allevents(src,evt)
    evname = evt.EventName;
    switch(evname)
        case {'MovingROI', 'ROIMoved'}
            linePosition = src.Position;
            x1 = linePosition(1, 1);
            y1 = linePosition(1, 2);
            x2 = linePosition(2, 1);
            y2 = linePosition(2, 2);
            lineLength = sqrt((x2 - x1)^2 + (y2 - y1)^2);
            disp(['length of the line: ', num2str(lineLength)]);
    end
end

Answer 1

[Walter Roberson]

Use wait to wait until the user finishes with the ROI. After that you can examine roi.Position and save that to an appropriate variable or return it from the function.