Radius Corporation

Paul Campbell

Martin Randall

Douglas J Gilbert

A method and apparatus for performing transparent data transfer operations on graphics data (such as video data), in which a source image currently displayed as part of a destination image (or stored in memory) is moved to a selected destination location on the destination image without obliterating background portions of the destination image. In a class of embodiments, the invention accomplishes a transparent bit-block transfer by clocking out source data (stored in an internal memory) to a bank of arithmetic logic units (ALUs), and processing the source data in the ALUs to identify portions of the source data representing transparent (or background) data which should not replace corresponding destination data, and which represent foreground data (new text to replace destination data). The marked source data are selectively written into a video memory containing the destination data, to selectively overwrite only those destination data pixels corresponding to new text. Transfers of source data to individual video memory locations which correspond transparent (background) data are inhibited or aborted.

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Berkeley, CA, United States of America

Paul Campbell