Dither volume with three thresholds for each cell location
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 colour component requires the retrieval of a different bit from the volume. Therefore in a multi threshold dither volume for digital halftoning a contone colour image, in the form of an array of contone colour 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 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 3 thresholds defining 4 intensity intervals within which said dither cell location is defined to an alternative not set and set.
2. A method of dithering a dither volume according to claim 1 , including the steps of dividing each dither cells into subcells, and storing each address of the subcells in separately addressable memories from which n thresholds are retrieved in parallel.
3. The method of dithering 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 3 threshold values are retrieved in parallel.
4. The method of dithering a dither volume according to claim 1 , comprising 256 layers.
5. The method of dithering a dither volume according to claim 4 , wherein the contone data is dithered using a triple threshold 64×64×3×8-bit.