Compaction of television display graphics in phantom-raster-scanned image memory

Claim 1

Apparatus for generating a video signal descriptive of an area in a raster-scanned display, said apparatus comprising: means for recurrently generating first and second series of digital electric signals respectively specifying in numeric form first and second orthogonal coordinates of phantom raster scan through said display area, there being a number m of signals in said first series and a number n of signals in said second series, where m and n may be equal or unequal integers; a display memory having a plurality of storage locations each accessable in response to a unique pair of column and row addresses for read-out of a video sample concerning a point in one of selected regions of said display area for which graphic information is stored in the display memory in compacted form, there being a number p of column addresses and a number q of row addresses, where p and q may be equal or unequal integers, where p is no larger than m and q is no larger than n, and where one of the numbers p and q is smaller than the number it is specified as being no larger than; means responsive to digital electric signals in said first series for generating purely in spatial coordinate terms corresponding column addresses for p selected ones of those digital electric signals; means responsive to digital electric signals in said second series for generating purely in spatial coordinate terms corresponding row addresses for q selected ones of those digital electric signals; means responsive to digital electric signals other than the p selected ones of said first series and q selected ones of said second series for supplying a source of video samples alternate to that provided by read-out of said display memory responsive to its being simultaneously addressed by column address generated responsive to a corresponding one of said p selected digital electronic signals of said first series and by column address generated responsive to a corresponding one of said q selected digital electric signals of said second series; and means responding to video samples read-out from said display memory in response to its said being simultaneously addressed, and to video samples supplied by said alternate source to provide said video signal.