Halftone dot thinning
View Patent ↗The invention provides techniques for thinning halftone dots in a halftone dot bit map. A bit map filter may be used to thin the dots. For example, a target glyph may passed over the bit map. If any subsets of bits within the bit map match the target glyph, the subsets of bits can be replaced with bits defined by a thinned glyph. In this manner, the ink of a halftone print can be reduced in a manner that enhances the visual appearance of the print.
1. A method of reducing ink coverage for inkjet printing comprising:
generating a monochromatic halftone bit map of a print to be printed by an inkjet printer; and
applying a bit map filter to the monochromatic halftone bit map to generate a filtered bit map for the inkjet printer, wherein applying the filter comprises comparing a target glyph to a subset of bits in the monochromatic halftone bit map, and replacing the subset of bits with a thinned glyph if the target glyph matches the subset of bits.
2. The method of claim 1 , wherein the monochromatic halftone bit map is a first monochromatic halftone bit map corresponding to a first colorant, the method further comprising:
generating a second monochromatic halftone bit map of the print, the second monochromatic halftone bit map corresponding to a second colorant; and
applying the bit map filter to the second monochromatic halftone bit map.
3. The method of claim 1 , further comprising printing a colorant of the print on a substrate according to the filtered bit map.
4. The method of claim 3 , further comprising examining the substrate and determining whether it is acceptable.
5. The method of claim 1 , further comprising:
passing the target glyph over the monochromatic halftone bit map;
comparing the target glyph to a number of subsets of bits; and
replacing a particular subset of bits with the thinned glyph whenever the target glyph matches the particular subset of bits.
6. The method of claim 1 , the method further comprising:
comparing a second target glyph to a second subset of bits in the monochromatic halftone bit map; and
replacing the second subset of bits with a second thinned glyph if the second target glyph matches the second subset of bits.
7. The method of claim 1 , further comprising detecting an edge of the print and ensuring that a bit corresponding to the edge is not changed by a thinned glyph.
8. The method of claim 1 , wherein the target glyph includes ON-bits and the thinned glyph includes ON-bits and OFF-bits.
9. The method of claim 8 , wherein the target glyph includes five ON-bits forming a plus shape and the thinned glyph includes four ON-bits and one OFF-bit.
10. The method of claim 9 , wherein thinned glyph forms a plus shape, the OFF-bit of the thinned glyph being in the center of the four ON-bits of the thinned glyph.
11. The method of claim 8 , wherein the target glyph includes three ON-bits and the thinned glyph includes two ON-bits and one OFF-bit, the OFF-bit being located between the two ON-bits in the thinned glyph.
12. The method of claim 8 , wherein the ON-bits indicate the presence of ink and the OFF-bits indicate the absence of ink.
13. The method of claim 8 , wherein the ON-bits indicate the presence of a first amount of ink and the OFF-bits indicate the presence of a second amount of ink.
14. The method of claim 1 , further comprising applying a mask prior to applying the filter, the mask defining areas of the monochromatic halftone bit map to which the filter is to be applied.
15. The method of claim 1 , wherein applying the bit map filter begins prior to finalizing the generating of the monochromatic halftone bit map.
16. The method of claim 1 , wherein generating the monochromatic halftone bit map of the print includes converting a number of halftone cells into the monochromatic halftone bit map, each halftone cell including a number of points that are selectively turned on to model a continuous tone pixel.
17. The method of claim 1 , wherein generating the monochromatic halftone bit map of the print includes a screening process that does not make use of halftone cells.
18. A method of reducing ink coverage for inkjet printing comprising:
comparing a target glyph to a subset of bits within a halftone bit map associated with a print to be printed by an inkjet printer; and
replacing the subset of bits within the halftone bit map with a thinned glyph if the target glyph matches the subset of bits to generate a filtered halftone bit map for the inkjet printer.
19. The method of claim 18 , further comprising:
passing the target glyph over the halftone bit map;
comparing the target glyph to a number of subsets of bits; and
creating the filtered halftone bit map by replacing a particular subset of bits with the thinned glyph whenever the target glyph matches the particular subset of bits.
20. The method of claim 19 , further comprising printing a print on a substrate according to the filtered halftone bit map.
21. The method of claim 20 , further comprising examining the substrate and re-defining the target glyph and thinned glyph if the substrate appears unacceptable.
22. The method of claim 21 , further comprising:
passing the re-defined target glyph over the halftone bit map;
comparing the re-defined target glyph to the number of subsets of bits; and
creating a second filtered halftone bit map by replacing a particular subset of bits with the re-defined thinned glyph whenever the re-defined target glyph matches the particular subset of bits.
23. A computer readable medium carrying program code that, when executed reduces ink coverage for inkjet printing by:
generating a monochromatic halftone bit map of a print to be printed by an inkjet printer; and
applying a bit map filter to the monochromatic halftone bit map to generate a filtered bit map, wherein applying the filter comprises comparing a target glyph to a subset of bits in the monochromatic halftone bit map, and replacing the subset of bits with a thinned glyph if the target glyph matches the subset of bits.
24. A computer readable medium carrying program code that reduces ink coverage for inkjet printing wherein the program code, when executed:
compares a target glyph to a subset of bits within a halftone bit map associated with a print to be printed by an inkjet printer; and
replaces the subset of bits within the halftone bit map with a thinned glyph if the target glyph matches the subset of bits to generate a filtered bit map for the inki et printer.
25. A system that reduces ink coverage for inkjet printing comprising:
a memory that stores a monochromatic halftone bit map associated with a print to be printed by an inkjet printer; and
a processor coupled to the memory that applies a bit map filter to the monochromatic halftone bit map to generate a filtered bit map for the inkjet printer, wherein the processor applies the bit map filter by:
passing the target glyph over the monochromatic halftone bit map;
comparing the target glyph to a number of subsets of bits; and
replacing a particular subset of bits with the thinned glyph whenever the target glyph matches the particular subset of bits to generate the filtered bit map.
26. The system of claim 25 , wherein the system is an inkjet printer.
27. The system of claim 25 , wherein the system is coupled to an inkjet printer.
28. A system that reduces ink coverage for inkjet printing comprising:
a memory that stores a halftone bit map associated with a print to be printed by an inkjet printer, a target glyph and a thinned glyph; and
a processor coupled to the memory that compares the target glyph to a subset of bits within the bit map, and replaces the subset of bits within the bit map with the thinned glyph if the target glyph matches the subset of bits to generate a filtered bit map for the inkjet printer.
29. The system of claim 28 , wherein the system is an inkjet printer.
30. The system of claim 28 , wherein the system is coupled to an inkjet printer.
31. A method of reducing ink coverage for a halftone printing device comprising:
generating a monochromatic halftone bit map of a channel of a color image to be printed by the halftone printing device; and
applying a bit map filter to the monochromatic halftone bit map to generate a filtered bit map for the halftone printing device by passing a target glyph over the monochromatic halftone bit map, comparing the target glyph to a number of subsets of bits in the monochromatic halftone bit map, and replacing a particular subset of bits with a thinned glyph when the target glyph matches the particular subset of bits, wherein applying the bit map filter begins prior to finalizing the generating of the monochromatic halftone bit map.