Problem drawing lines by dragging the mouse

Question

0 个投票

I want to draw a set of disconnected lines on top of an image by dragging the mouse while the left button is pressed. However, if I click on a previously drawn line to specify the starting point of the next line, the callback function is not being called and I don't get the point. Here is my code:

 function main_test
 S.fH = figure('menubar','none');
 im = imread( 'image.jpg' );
 S.aH = axes;
 S.iH = imshow( im ); hold on
 axis image;
 X = [];
 Y = [];
 set(S.aH,'ButtonDownFcn',@startDragFcn)
 set(S.iH,'ButtonDownFcn',@startDragFcn)
 set(S.fH, 'WindowButtonUpFcn', @stopDragFcn);
    function startDragFcn(varargin)
        set( S.fH, 'WindowButtonMotionFcn', @draggingFcn );
        pt = get(S.aH, 'CurrentPoint');
        x = pt(1,1);
        y = pt(1,2);
        X = x;
        Y = y;
    end
    function draggingFcn(varargin)
        pt = get(S.aH, 'CurrentPoint');
        x = pt(1,1);
        y = pt(1,2);
        X = [X x];
        Y = [Y y];
        plot(X, Y, 'r', 'LineWidth', 6);
        hold on
        drawnow 
    end
    function stopDragFcn(varargin)
        set(S.fH, 'WindowButtonMotionFcn', '');  %eliminate fcn on release
    end
 end