I wrote the Matlab GUI script below in App Designer in order to select an image ROI:

function markROIButtonPushed(app, event)
            function allevents(src,evt)
                evname = evt.EventName;
                switch(evname)
                    case{'MovingROI'}
                        disp(['ROI moving previous position: ' mat2str(evt.PreviousPosition)]);
                        disp(['ROI moving current position: ' mat2str(evt.CurrentPosition)]);
                        pos = roi.Position;
                        app.col1 = floor(pos(1)); % Column 1
                        app.col2 = ceil(pos(1) + pos(3)); % Column 2
                        app.row1 = floor(pos(2));   % Row 1
                        app.row2 = ceil(pos(2) + pos(4));   % Row 2
                        app.x1Crop = app.col1;
                        app.y1Crop = app.row1;
                    case{'ROIMoved'}
                        disp(['ROI moved previous position: ' mat2str(evt.PreviousPosition)]);
                        disp(['ROI moved current position: ' mat2str(evt.CurrentPosition)]);
                        pos = roi.Position;
                        app.col1 = floor(pos(1)); % Column 1
                        app.col2 = ceil(pos(1) + pos(3)); % Column 2
                        app.row1 = floor(pos(2));   % Row 1
                        app.row2 = ceil(pos(2) + pos(4));   % Row 2
                        app.x1Crop = app.col1;
                        app.y1Crop = app.row1;
                end
            end

            imshow(app.I,'Parent', app.imageAxes);
            roi = drawrectangle(app.imageAxes);
            [app.Iy1,app.Ix1,app.Iz1] = size(app.I);

            addlistener(roi,'MovingROI',@allevents);
            addlistener(roi,'ROIMoved',@allevents);
            pos = roi.Position;
            app.col1 = floor(pos(1)); % Column 1
            app.col2 = ceil(pos(1) + pos(3)); % Column 2
            app.row1 = floor(pos(2));   % Row 1
            app.row2 = ceil(pos(2) + pos(4));   % Row 2
            app.x1Crop = app.col1;
            app.y1Crop = app.row1;
 
            if  app.col1 < 1
                app.col1 = 1;
            end

            if  app.row1 < 1
                app.row1 = 1;
            end

            if  app.col2 > app.Ix1
                app.col2 = app.Ix1;
            end

            if  app.row2 > app.Iy1
                app.row2 = app.Iy1;
            end 
        end

        % Button pushed function: selectROIButton
        function selectROIButtonPushed(app, event)
           app.Icrop = app.I(app.row1 : app.row2, app.col1 : app.col2, :)
            disp(app.col1)
            disp(app.row1)
            app.RoiOn = true;
            app.ROISwitch.Enable = 'off';
        end

But when I wish to start to mark the ROI from the image coordinates (1,1) for the upper-left corner of the image I get this error “Index in position 2 is invalid. Array indices must be positive integers or logical values.”

The same issue will appear in the lower-left corner of the image (error: "Index in position 1 exceeds array bounds. Index must not exceed...")?

How can I solve it?