| 摘要 |
A digital screener for digitally converting a continuous tone color separation into a corresponding high resolution, bit-mapped, raster scanned halftone separation of an original artwork which utilizes a contone line buffer (913), an image handler (930), a screen handler (950), and a font memory (970). For every successive micro raster that is to occur in the screened image, the screen handler repetitively generates appropriate sampling coordinates, using predefined fast and slow scan incremental values, in order to sample any of the halftone reference patterns along successively positioned angled sampling lines (710, 730) that collectively form an angled grid so as to provide a bit-mapped halftone image pattern oriented at a desired screen angle. The font memory stores a different halftone dot pattern for each different contone value. Each contone value and simultaneously occurring sampling coordinates form addresses to the font memory for selecting a particular sampled reference halftone dot pattern while the sampling coordinates are used to access a particular bit within that pattern. The image handler and the screen hander operate essentially independently of each other for pipelined operation to increase throughput. |
