Manipulation - (ma-nip-u-la-tion) 

1. a. the act or practice of manipulating.

    b. the state of being manipulated. 

2. shrewd or devious management, especially for one's own advantage.

The act of manipulating an image, or anything for that matter, is in my opinion a deliberate and premeditated process. The manipulator sets about changing certain visual aspects in order to relay a different message through the image.