Methods for fast scrolling of images

摘要

Fast scrolling of images can be achieved by drawing only the portions that are changed as a result of scrolling. Because there is no need to draw the whole image during scrolling, the scrolling speed can be increased. This method can be applied to bitmap and vector images. A high speed data transfer device can also be used to further increase scrolling speed. This device comprises two memory buffers, a first circuit for communicating data with a hard disk, and a second circuit for communicating data with system memory. The device also comprises a data switching circuit which alternative couples the first circuit to one of the two buffers and alternatively couples the second circuit to the remaining one of the two buffers. As a result, graphic data can be continuously transfer between the hard disk and system memory. Consequently, scrolling can be performed without slowed down by data transfer.