//! Rotates points around center.
/*! This is a quite straight method, it calculates in pixels
* and so it produces rounding errors.
* \param points The points inside will be rotated.
* \param angle Rotating angle (counterclockwise, start at 3 o'clock, 360 is full circle).
* \param center Center of rotation.
//! Rotates points around center.
/*! This is a quite straight method, it calculates in pixels
* and so it produces rounding errors.
* \param points The points inside will be rotated.
* \param angle Rotating angle (counterclockwise, start at 3 o'clock, 360 is full circle).
* \param center Center of rotation.