GRAPHICS IMAGE RELOCATION FOR DISPLAY VIEWPORTING AND PEL SCROLLING

摘要

GRAPHICS IMAGE RELOCATION FOR DISPLAY VIEWPORTINGAND PEL SCROLLINGABSTRACTBy selecting the starting time of the display readout of apel buffer raster generation, the pel date is mapped to adisplay screen with an arbitrary displacement with respect tothe screen for relocation or scrolling of the pel image on thescreen. To compensate for non-congruency between the pel datawindow and screen viewport definitions and to provide scrollingon a pel basis, the positioning of the window on the screenincludes fine adjustment achieved by a determinable delaybetween the scanning of the buffer and the generation of thescreen raster. The display circuits include means to extendthe window background to fill in gaps between the edges of awindow of pel data chosen to be displayed and a larger screenviewport in which it is to be displayed. System read/writeaccess times to the buffer are interleaved with andsynchronized to the data fetch times of the display.