Activate the window in which the target image is located. To do this, click the left mouse button on the window area or header (marked by the arrow in Fig. 5.25).
Click on the arrow on the right side of the Rotate 
button and select the angle
from the drop-down menu.
To restore the initial image position, select the Set image rotation angle 0° item.
To rotate an image by an arbitrary angle, activate the Rotate tool by clicking
the left/right/middle mouse button. To continue work with this tool, use the button with
which the tool was activated. To learn more about tool control, see Section 1.14. Rotate
the image by moving the mouse while holding down the button that activated the tool.
.
