Abstract: A method for increasing the speed of color conversion from a plurality of color spaces to a single color space by reducing the number of color pixels by a factor of two prior to the color conversion step. This pixel reduction constitutes a lossy data compression scheme which takes advantage of the advance knowledge that the pixels will later undergo anti-aliasing by averaging subsequent to the color conversion. First the pixels are grouped into pairs, and one pixel of each pair is eliminated to form a pseudo halfpixel. The eliminated pixel is replaced with a tag identifying either the previous, current or next pseudo halfpixel. Then each pseudo halfpixel is color converted. Finally the indicated previous, current or next pseudo halfpixel, now color converted, is averaged with the current pseudo halfpixel to form a halfpixel, which is then averaged with the halfpixel above or below it to form an anti-aliased full pixel which can be displayed.

Abstract: A circuit for rapidly rotating a digital image through 90 or 270 degrees utilizing memory implemented from ordinary 4-bit wide memory devices. This pipelined circuit transfers the image through a page buffer and a band buffer in a series of memory accessing, shining and reordering steps which converts all vertical lines to horizontal lines and all horizontal lines to vertical lines without requiring the use of a parallel to serial conversion.