| 摘要 |
<p>Image data (10) is represented by a plurality of scan lines (30). Each scan line (30) includes a line of pixels (32) along a fast scan access. Each pixel (32) represents an optical density for a specific location in the image data (10). Pairs of pixels in the fast scan direction of odd numbered scan lines (30) are grouped in even/odd pixel pairs by logic circuit (12). Pairs of pixels of even numbered scan lines (3) are grouped in odd/even pixel pairs such that the groupings in adjacent lines are offset. Each pixel pair contains n addressability units defining a halftone cell. The addressability units of the pixel pair are combined. A propagated error value from a previous pixel pair and the data values of each pixel pair are combined and used to address a memory location in a look-up table (14). The memory location contains a corresponding binary data value representing an intensity level for each pixel of the pixel pair. The binary data is outputted to a gray modulator (16) to be printed by a printer (18). The outputted data grid is equivalent to a very high frequency halftone screen having a Moiré pattern not visually perceivable. <IMAGE></p> |
