Calculates an affine matrix of 2D rotation

M = cv.getRotationMatrix2D(center, angle, scale)

Input

• center Center of the rotation in the source image [x,y].
• angle Rotation angle in degrees. Positive values mean counter-clockwise rotation (the coordinate origin is assumed to be the top-left corner).
• scale Isotropic scale factor.

Output

• M The output affine transformation, 2x3 double matrix.

The function calculates the following matrix:

[ a, b, (1-a)*center(1) - b*center(2) ;
 -b, a, b*center(1) + (1-a)*center(2) ]

where:

a = scale * cos(angle)
b = scale * sin(angle)

The transformation maps the rotation center to itself. If this is not the target, adjust the shift.