Dear pangfengjiang,
if the image you are grabbing is already too large for the memory, you will not be able to avoid a larger grabber.
Have you already looked at the examples under "GeometricTransformation"? This describes the geometric transformations, including rotation.
You should find an example in: C:\Program Files\Basler\VisualApplets_3.3\Examples\Processing\Geometry\GeometricTransformation
Best regards
Matthias