Horizontal and vertical image inversion circuit for a video display

Claim 1

In a video display system including a computer, a CRT, and means for displaying images which may include graphic displays on said CRT under control of said computer including an image memory which receives image data including graphic display data from the computer for subsequent display on said CRT, the image memory comprising a pixel memory map of the image to be display on the CRT, the improvement comprising means for writing the image data into said image memory in one of two selectable modes, namely, left to right or right to left; the means for writing including address generating means and first address memory means operatively disposed between the address generating means and the image memory, the first address memory means having selectable first and second address spaces, said first and second address spaces adapted to access the image memory, respectively, from left to right and right to left writing modes; means for reading the image data from said image memory for subsequent display on said CRT in one of two selectable modes, namely, top to bottom or bottom to top, the means for reading including said address generating means and second address memory means operatively disposed between the address generating means and the image memory, the second address memory means having selectable third and forth address spaces, said third and forth address spaces adapted to access the image memory, respectively, from top to bottom and bottom to top; and means operatively connected to said first and second address memory means for controlling said writing and reading means whereby the image displayed on said CRT may be normal, inverted or partially inverted when viewed from a fixed position.