Fix crash of image_rotation() for +-90 degrees (issue #16)

In the corner cases, sine and cosine values are assigned exactly.
Together with an additional '+1' in the Nx and Ny computation,
this fixes the issue.
Fix crash of image_rotation() for +-90 degrees (issue #16)

In the corner cases, sine and cosine values are assigned exactly.
Together with an additional '+1' in the Nx and Ny computation,
this fixes the issue.
resolve conflict
resolve conflict