How do I draw two lines on an image using the mouse and get the angle between the lines?

I have an image in a figure window and I would like to use the mouse to draw two lines on the image.

For example, say I have a satellite image of an airplane on landing approach to a runway. I want to draw one line through the center of the airplane along the direction of flight and a second line down the center of the runway. I want MATLAB to determine the angle between these lines.

Answer 1

[MathWorks Support Team]

This script file demonstrates how this can be done.

% function theta = measureAngle

% Get four mouse clicks from the user in the current figure

[x,y] = ginput(4);

% Draw the two lines that the four points represent

line(x(1:2), y(1:2));

line(x(3:4), y(3:4));

% Define the two vectors

v1 = [x(2) - x(1), y(2) - y(1)];

v2 = [x(4) - x(3), y(4) - y(3)];

% Compute the angle from v1 to v2

theta = acosd(dot(v1, v2) / (norm(v1) * norm(v2)) )

% end