US Patent 7944586 Page expansion and printing method

A page expansion and printing procedure requires a first page description into a first memory buffer, the first page description having a bi-level black layer and a contone CMYK layer; decompressing the bi-level black layer and the contone CMYK layer in parallel; half-toning the contone CMYK layer to bi-level CMYK; compositing the bi-level black layer over the bi-level CMYK layer to form a printable image; and transmitting the printable image to a second memory buffer for printing by the pagewidth printer. The step of transmitting the printable image to a second memory buffer is performed simultaneously with receiving a subsequent page description in the first memory buffer.