Realtime Rotation and Mirror Transformation of Square Images
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
This invention concerns a control of some subset of square image transformations, particularly +90, -90 and 180 degree rotation and mirror imaging relative to horizontal or (and) vertical axes. It is especially suitable for frame buffered raster displays and, to some extent, to stroke displays using an extra memory for font representation. A general approach to two-dimensional transformations uses two systems of equation, one for rotation around the center of transforming area: X' = X Cos O + Y Sin O (1) Y' = -X Sin O + Y Cos O (2) where O - clockwise angle of rotation X,Y - former coordinate of pixel X',Y' - new coordinate of pixel, and a special case of one for rotation to produce mirror images: X' = X Sx Y' = Y Sy where Sx, Sy are +1 or -1.