matlab

How to calculate Gradient 'direction' (not magnitude) of image along x and y axis in matlab?

I used imgradientxy() ;but it gives values like -600.i need values of angle in range -180 to 180. in both direction separately.

Solution

  • The values are 0 and 90. The gradient is calculated in the X and Y direction by imgradientxy() as you may infer from its name.

    However the gradient in a point is defined by:

    enter image description here

    and you can do [Gx,Gy]=imgradientxy(img).

    That means that your total gradient (not the "directional gradient", which is what Gx and Gy are) is a vector. the (Gxi,Gyi) vector in point i.

    To calculate the modulus and angle of a vector is a straightforward algebra thing:

    The modulus, magnitude, euclidean norm or however you preffer to call it is:

    m=norm([Gx,Gy]);

    And the angle:

    theta=atan2(Gy,Gx); %radians
theta=atand(Gy/Gx); %degrees