Patent US 4,168,488

This specification describes image rotation hardware for allowing the displaying of an image stored in digital form in other than its originally stored orientation. In this hardware a word-organized image buffer stores a digital representation of a full image with each picture element (pel) of the full image being represented by a bit within the buffer. The buffer is divided into a plurality of square sections each storing a portion or subimage of the full image. Each section is n.times.n bits in size where n is the number of bits in a word stored in the buffer. The contents of each square section of the buffer can be transferred into an n.times.n storage array with first word organization, and then transferred back into the buffer with second word organization such that the subimage stored by the square section is rotated through 90.degree..