need help using setPositionConstraintFcn

I want to use the imline tool to enable the user to draw a horizontal line on an image. From what I can tell I need to use setPositionConstraintFcn to assign constraints on imline but I can't figure out the syntax for this. Help is appreciated.

Answer 1

[CC]

Here is one example

h1=imline(handles.axes1,[0.5 0;0.5 8]);  %the initial and end point positions 
setColor(h1,[1 0 0])  % red color
fcn = makeConstrainToRectFcn('imline',[0 5],[-2 10]); % on x-axis, move between 0to 5, on y-axis, move between -2 to 10
setPositionConstraintFcn(h1,fcn);