Emulation of a halftone printed image on a continuous-tone device
First Claim
1. A method for emulating a halftone printed image on a continuous-tone device, said image being defined by N color separation bitmaps, and said continuous-tone device being capable of producing one of a continuous range of colors at each of a plurality of first addressable units, the method comprising the steps of:
- (a) constructing a halftone device model defined by a plurality of second addressable units and a plurality of device spots, said device spots being sized larger than said second addressable units such that said device spots produce a plurality of overlap regions within each of said second addressable units when addressed to said second addressable units;
(b) addressing said device spots to said second addressable units based on said N color separation bitmaps, wherein each of said device spots is assigned one of N different colors determined by colors associated with said N color separation bitmaps, said device spots forming, with said overlap regions, a maximum of 2N different colors within each of said second addressable units;
(c) dividing each of said second addressable units into K addressable sub-units;
(d) determining, for each of said 2N different colors, the number of said sub-units in which the respective one of said 2N different colors is formed;
(e) dividing, for each of said 2N different colors, the number of said sub-units in which the respective one of said 2N different colors is formed by the total number K of said sub-units, thereby calculating fractional values for each of said 2N different colors;
(f) calculating a set of color values for each of said second addressable units based on the fractional values calculated for each of said 2N different colors formed in the respective one of said second addressable units; and
(g) controlling said continuous-tone device to produce one of said continuous range of colors at each of said first addressable units based on the set of color values calculated for one or more of said second addressable units, thereby emulating said halftone printed image on said continuous-tone device.
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Abstract
A system and method for representing a multi-color, halftone image on a multi-color, continuous-tone device can be configured to employ an approximation technique for determining areas of overlap regions produced by adjacent device spots in a printed halftone image based on a halftone device model. The approximation technique enables consideration of the effects of a variety of halftone device characteristics such as addressability, device spot size, and color values on the appearance of a printed halftone image. The system and method can be configured to employ the approximation technique in a manner that also enables consideration of the effect of misregistration between color separations on the appearance of a printed halftone image. As an alternative, the system and method can be configured to employ a geometrical abstract that effectively centers device spots on the corners of addressable units. This "corner-centered" addressing enables a computationally faster calculation of overlaps when used with either the approximation technique or an analytical technique based on geometric relationships, particularly for device spot diameters between a factor of √2 and 2 of the addressability of the halftone device. Finally, the system and method may incorporate a technique for scaling the addressability of color values representative of the halftone printed image without introducing significant artifacts.
60 Citations
42 Claims
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1. A method for emulating a halftone printed image on a continuous-tone device, said image being defined by N color separation bitmaps, and said continuous-tone device being capable of producing one of a continuous range of colors at each of a plurality of first addressable units, the method comprising the steps of:
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(a) constructing a halftone device model defined by a plurality of second addressable units and a plurality of device spots, said device spots being sized larger than said second addressable units such that said device spots produce a plurality of overlap regions within each of said second addressable units when addressed to said second addressable units; (b) addressing said device spots to said second addressable units based on said N color separation bitmaps, wherein each of said device spots is assigned one of N different colors determined by colors associated with said N color separation bitmaps, said device spots forming, with said overlap regions, a maximum of 2N different colors within each of said second addressable units; (c) dividing each of said second addressable units into K addressable sub-units; (d) determining, for each of said 2N different colors, the number of said sub-units in which the respective one of said 2N different colors is formed; (e) dividing, for each of said 2N different colors, the number of said sub-units in which the respective one of said 2N different colors is formed by the total number K of said sub-units, thereby calculating fractional values for each of said 2N different colors; (f) calculating a set of color values for each of said second addressable units based on the fractional values calculated for each of said 2N different colors formed in the respective one of said second addressable units; and (g) controlling said continuous-tone device to produce one of said continuous range of colors at each of said first addressable units based on the set of color values calculated for one or more of said second addressable units, thereby emulating said halftone printed image on said continuous-tone device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for emulating a halftone printed image on a continuous-tone device, said image being defined by N color separation bitmaps, and said continuous-tone device being capable of producing one of a continuous range of colors at each of a plurality of first addressable units, the method comprising the steps of:
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(a) constructing a halftone device model defined by a plurality of second addressable units and a plurality of device spots, wherein each of said second addressable units defines a substantially rectangular area having four corners, wherein each of said device spots is a substantially circular device spot having a radius, wherein each of said device spots, when addressed, has a center substantially centered on one of the corners of one of said second addressable units, and wherein said device spots have sizes greater than sizes of said second addressable units such that said device spots produce a plurality of overlap regions within each of said second addressable units when addressed to said second addressable units; (b) addressing said device spots to said second addressable units based on said N color separation bitmaps, wherein each of said device spots is assigned one of N different colors determined by colors associated with said N color separation bitmaps, said device spots forming, with said overlap regions, a maximum of 2N different colors within each of said second addressable units; (c) dividing each of said second addressable units into a plurality of overlap regions; (d) determining, for each of said second addressable units, the one of said 2N different colors formed within each of said overlap regions in the respective one of said second addressable units; (e) calculating, for each of said second addressable units, fractional values for each of said 2N different colors formed within said overlap regions in the respective one of the second addressable units, the fractional values being calculated based on a ratio of the sums of areas of the respective overlap regions in which the respective one of said 2N different colors is formed to a total area of the respective one of the second addressable units; (f) calculating a set of color values for each of said second addressable units based on the fractional values calculated for each of said 2N different colors formed in the respective one of said second addressable units; and (g) controlling said continuous-tone device to produce one of said continuous range of colors at each of said first addressable units based on the set of color values calculated for one or more of said second addressable units, thereby emulating said halftone printed image on said continuous-tone device. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A system for emulating a halftone printed image on a continuous-tone device, said image being defined by N color separation bitmaps, and said continuous-tone device being capable of producing one of a continuous range of colors at each of a plurality of first addressable units, the system comprising:
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(a) means for constructing a halftone device model defined by a plurality of second addressable units and a plurality of device spots, said device spots being sized larger than said second addressable units such that said device spots produce a plurality of overlap regions within each of said second addressable units when addressed to said second addressable units; (b) means for addressing said device spots to said second addressable units based on said N color separation bitmaps, wherein each of said device spots is assigned one of N different colors determined by colors associated with said N color separation bitmaps, said device spots forming, with said overlap regions, a maximum of 2N different colors within each of said second addressable units; (c) means for dividing each of said second addressable units into K addressable sub-units; (d) means for determining, for each of said 2N different colors, the number of said sub-units in which the respective one of said 2N different colors is formed; (e) means for dividing, for each of said 2N different colors, the number of said sub-units in which the respective one of said 2N different colors is formed by the total number K of said sub-units, thereby calculating fractional values for each of said 2N different colors; (f) means for calculating a set of color values for each of said second addressable units based on the fractional values calculated for each of said 2N different colors formed in the respective one of said second addressable units; and (g) means for controlling said continuous-tone device to produce one of said continuous range of colors at each of said first addressable units based on the set of color values calculated for one or more of said second addressable units, thereby emulating said halftone printed image on said continuous-tone device. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. A system for emulating a halftone printed image on a continuous-tone device, said image being defined by N color separation bitmaps, and said continuous-tone device being capable of producing one of a continuous range of colors at each of a plurality of first addressable units, the system comprising:
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(a) means for constructing a halftone device model defined by a plurality of second addressable units and a plurality of device spots, wherein each of said second addressable units defines a substantially rectangular area having four corners, wherein each of said device spots is a substantially circular device spot having a radius, wherein each of said device spots, when addressed, has a center substantially centered on one of the corners of one of said second addressable units, and wherein said device spots have sizes greater than sizes of said second addressable units such that said device spots produce a plurality of overlap regions within each of said second addressable units when addressed to said second addressable units; (b) means for addressing said device spots to said second addressable units based on said N color separation bitmaps, wherein each of said device spots is assigned one of N different colors determined by colors associated with said N color separation bitmaps, said device spots forming, with said overlap regions, a maximum of 2N different colors within each of said second addressable units; (c) means for dividing each of said second addressable units into a plurality of overlap regions; (d) means for determining, for each of said second addressable units, the one of said 2N different colors formed within each of said overlap regions in the respective one of said second addressable units; (e) means for calculating, for each of said second addressable units, fractional values for each of said 2N different colors formed within said overlap regions in the respective one of the second addressable units, the fractional values being calculated based on a ratio of the sums of areas of the respective overlap regions in which the respective one of said 2N different colors is formed to a total area of the respective one of the second addressable units; (f) means for calculating a set of color values for each of said second addressable units based on the fractional values calculated for each of said 2N different colors formed in the respective one of said second addressable units; and (g) means for controlling said continuous-tone device to produce one of said continuous range of colors at each of said first addressable units based on the set of color values calculated for one or more of said second addressable units, thereby emulating said halftone printed image on said continuous-tone device. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42)
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Specification