Dither volume with multiple thresholds for each cell
View Patent ↗While a general large layer dither volume provides great flexibility in dither cell design, by decoupling different intensity levels, they are inefficient to access since each color component requires the retrieval of a different bit from the volume. Therefore in a multi threshold dither volume for digital halftoning a contone color image, in the form of an array of contone color pixel values to bi-level dots, there is allocated for each dither cell location a fix set of n thresholds defining n+1 intensity intervals within which said dither cell location is defined to be alternatively not set and set.
1. A dither volume for digital halftoning a contone image, in the form of an array of contone color pixel values, to bi-level dots, said dither volume comprising for each dither cell location, a fixed set of n thresholds defining n+1 intensity levels within which said dither cell location is defined to be alternately not set and set.
2. A dither volume according to claim 1 wherein each dither cell is split into subcells and stored in separately addressable memories from which said different n threshold values are retrieved in parallel.
3. A dither volume according to claim 1 comprising 256 layers.
4. A method of dithering a dither volume, for digital halftoning a contone image, in the form of an array of contone color pixel values, to bi-level dots, comprising the steps of:
assigning for each dither cell location a fixed set of n thresholds defining n+1 intensity intervals within which said dither cell location is defined to an alternative not set and set.
5. A method of dithering a dither volume according to claim 4 , including the steps of dividing each dither cells into subcells, and
storing each address of the subcells in separately addressable memories from which said n thresholds are retrieved in parallel.