This function rotates the PixMap image clockwise. The rotation
angle must be a multiple of 90. If an invalid number of degrees is
specified, then an ArgumentOutOfRangeException will be thrown.
An image may have an associated bit mask or soft (alpha) mask.
If this is the case, the associated mask will be transformed as
When a PixMap is drawn on a page, it is scaled to fit into a
particular location. The scaling is separate from the PixMap
itself. Rotating by 90 or 270 degrees will swap the width and
height of the PixMap. Because the scaling of drawn copies is
separate from the PixMap itself, any previously drawn instances of
the PixMap may appear to have an incorrect aspect ratio.
After the Bitmap has been set, the PixMap will be uncompressed.
You may wish to compress it using a call like CompressJpeg or CompressFlate.