Abstract: A system for generating a set of bit masks arrays is provided (350-0 to 350-255) where the bit mask arrays (350-0 to 350-255) are such that clusters of entries of different types are spread across each array and entries of different types within the arrays are either part of a larger cluster of entries of that type or are immediately adjacent to a cluster of entries of that type. When a multi-level image (200) is converted to a half-tone image (300) utilizing the bit mask arrays (350-0 to 350-255) a half-tone image (300) which limits the occurrence of small isolated printed or unprinted areas is generated. The bit mask arrays (350-0 to 350-255) are therefore particularly suitable for use with laser printers (28,32) which have difficulty rendering half tone images which comprise small isolated printed and unprinted areas.

Abstract: A printing system is disclosed where a multi level pixel image (200) is converted into a half tone image (300) utilising a set of bit mask arrays (350-0 to 350-255) stored within a memory (310). The value of a multi level pixel is used to select one of the stored bit mask arrays. The co-ordinates of the multi level pixel in an image are then used to identify an entry from within the selected bit mask array. The identified entry is then used to set the value of the corresponding pixel in the half tone image. In order to reduce the appearance of contouring at the boundaries of adjacent portions of an image having similar grey levels, the stored bit mask arrays (350-0 to 350-255) are such that the majority of entries in the bit mask arrays for successive grey levels are identical. In addition to reducing contouring problems, the similarity of significant portions of bit mask arrays for successive grey levels make the bit mask arrays suitable for compression.

Abstract: A printing system is disclosed where a multi level pixel image (200) is converted into a half tone image (300) utilising a set of bit mask arrays (350-0 to 350-255) stored within a memory (310). The value of a multi level pixel is used to select one of the stored bit mask arrays. The co-ordinates of the multi level pixel in an image are then used to identify an entry from within the selected bit mask array. The identified entry is then used to set the value of the corresponding pixel in the half tone image. In order to reduce the appearance of contouring at the boundaries of adjacent portions of an image having similar grey levels, the stored bit mask arrays (350-0 to 350-255) are such that the majority of entries in the bit mask arrays for successive grey levels are identical. In addition to reducing contouring problems, the similarity of significant portions of bit mask arrays for successive grey levels make the bit mask arrays suitable for compression.