| 摘要 |
Multi level pixel image data is converted into half tone image data using a set of bit mask arrays 350-0 to 350-255 stored in memory. In order to reduce the appearance of contouring between regions represented by similar grey levels, the bit mask arrays are arranged such that the number of differences for arrays representing similar shades (eg 350-224 and 350-225) is kept below a threshold value, ensuring a smooth transition between grey levels. Also disclosed is a printing method wherein the majority of dots in a half tone arrangement for a particular shade are included in a subset of the dot arrangement for a similar, but darker, shade. A method for compressing/decompressing bit mask data involving subjecting bit mask data values to exclusive OR operations prior to run-length encoding is described. |
