Overlapping drop assignment for multi-level ink jet printing
View Patent ↗To avoid the image artifacts of a uniform drop-per-pixel, a drop assignment overlap is introduced. Larger and lower drops are printed simultaneously to represent uniform gray level. The regions at which the first number of drops and the second number of drops are put down overlap. Thus, a pattern in which a uniform number of drops is put down at every pixel is eliminated, and a pattern of overlapping first and second drops is obtained.
1. An method for forming an image using an image processing device, comprising:
inputting image data representing an image to produce an input level for each pixel of a plurality of pixels that reproduce the image by a plurality of print elements;
mapping from the input level to a mapping level for each pixel;
determining drop assignment values for the pixel from the mapping levels to provide a multi-level output value that assigns none, one or more than one of the print elements corresponding to the pixel, the drop assignment values corresponding to their respective print elements; and
forming a reproduced image based on the plurality of pixels and the determined drop assignment values, wherein the drop assignment values overlap in accordance with the multi-level output value.
2. The image processing method of claim 1 , further comprising running independent drop assignment routines for the mapping.
3. The image processing method of claim 2 , wherein one of the drop assignment routines is error diffusion, wherein the mapping levels are error diffusion levels.
4. The image processing method of claim 2 , wherein one of the drop assignment routines is half-toning.
5. The image processing method of claim 2 , wherein a gray level introduced by one of the drop assignment routines is lower than another of the drop assignment routines.
6. The image processing method of claim 1 , wherein the drop assignment includes assigning various drop sizes to at least two levels.
7. The image processing method of claim 1 , wherein the drop assignment includes assigning various numbers of drops to at least two levels.
8. The image processing method of claim 1 , wherein the drop assignment includes assigning various drop sizes to at least two levels.
9. The image processing method of claim 1 , wherein the drop assignment includes assigning drops of varying concentration to at least two levels.
10. The image processing method of claim 1 , comprising running one drop assignment routine.
11. An image processing device, comprising:
an image data input device that inputs image data representing an image to produce an input level for each pixel of a plurality of pixels that reproduce the image by a plurality of print elements;
a mapping circuit that maps the pixel from the input level to mapping levels;
a drop assignment determination circuit that determines drop assignment values for the pixel from the mapping levels to provide a multi-level output value that assigns none, one or more than one of the print elements corresponding to the pixel, the drop assignment values corresponding to their respective print elements; and
an imager that forms a reproduced image based on the plurality of pixels and the determined drop assignment values, wherein the drop assignment values overlap in accordance with the multi-level output value.
12. The image processing device of claim 11 , further comprising a drop assignment circuit that runs independent drop assignment routines for the mapping circuit.
13. The image processing device of claim 12 , wherein one of the drop assignment routines is error diffusion, wherein the mapping levels are error diffusion levels.
14. The image processing device of claim 12 , wherein one of the drop assignment routines is half-toning.
15. The image processing device of claim 12 , wherein a gray level introduced by one of the drop assignment routines is lower than another of the drop assignment routines.
16. The image processing device of claim 11 , wherein the drop assignment includes assigning various drop sizes to each level.
17. The image processing device of claim 11 , wherein the drop assignment includes assigning various number of drops to each level.
18. The image processing device of claim 11 , wherein the drop assignment includes assigning various drop sizes to each level.
19. The image processing device of claim 11 , wherein the drop assignment includes assigning drops of varying concentration to each level.
20. The image processing device of claim 11 , comprising a drop assignment circuit that runs one drop assignment routine.