This lets you rotate the image by an arbitrary angle. Positive values rotate to the right (clockwise) and negative values to the left (counterclockwise). For example, if you enter "27," your image will be rotated 27 degrees to the right, "-27" would rotate it 27 degrees to the left.
Interpolate pixels If checked, the pixels in the new image will be calculated using a pixel average method. Using resampling is much slower, but gives a far better result. Rotating an image without resampling may cause aliasing effects. For example, the image below has been rotated without resampling. You may notice that the rotation has caused the Mona Lisa's left eye to disappear. This would not have occurred if resampling had been used. Note that the image will be converted to RGB deep color when resampling is used.
Example of 45° degree rotation:
The original bitmap
Rotated by 45 degrees