EP0342845A1
Expired / Lapsed
EP
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Producing half-tone images
Assignee: Crosfield Electronics Ltd
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Filing: 1989-05-09
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Granted: —
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Expires: 2009-05-09
Abstract
Abstract A method and apparatus for generating a half-tone version of an image represented by a first set of digital data defining the colour content of abutting pixels of the image at a first resolution. The apparatus comprises a radiation beam generator (8); a record medium support (11), wherein the radiation beam and the support are relatively moveable such that the radiation beam scans a record medium (10) mounted on the support in a series of abutting scan lines; a radiation beam modulator (7) for modulating the radiation beam in response to a control signal (CS); and a control signal generator (5) for generating the control signal. The radiation beam is modulated selectively to expose a record medium on the support (11) at a second, finer resolution, the control signal generator (5) being adapted to interpolate the second set of digital data from the first set of digital data and to generate the control signal by comparing the second set of digital data with half-tone information.
Inventors
- 👤 Graham Webb
- 👤 Richard Anthony Kirk
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 15:10
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/40068; G; G06; G06T; G06T3/00; G06T3/40; G06T3/4007; H04N1/405; H04N1/4055
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
87 words
A method of generating a half-tone version of an image represented by a first set of digital data defining the colour content of abutting pixels of the image at a first resolution in which a record medium is selectively exposed in response to a control signal representing image pixels at a second, finer resolution, the control signal being generated by comparing the second set of digital data with half-tone information characterised by at least partly interpolating the second set of data from the first set of data.
Claim 2
Independent Claim
87 words
A method of generating a half-tone version of an image represented by a first set of digital data defining the colour content of abutting pixels of the image at a first resolution in which a record medium is selectively exposed in response to a control signal representing image pixels at a second, finer resolution, the control signal being generated by comparing the second set of digital data with half-tone information characterised by at least partly interpolating the second set of data from the first set of data.
Claim 3
Dependent Claim
76 words
A method according to claim 1, wherein the half-tone information defines an array of half-tone dot elements at the second resolution, each element being associated with a respective threshold value, whereby each pixel at the second resolution is compared with the threshold values of a respective section of the half-tone dot elements chosen in accordance with the relative position of the exposing beam within a half-tone dot portion in order to generate the control signal (CS).
Claim 4
Dependent Claim
22 words
A method according to claim 2, wherein each half-tone dot section comprises a square array of dot elements at the second resolution.
Claim 5
Independent Claim
63 words
A method according to any of the preceding claims, wherein the second set of digital data is obtained from the first set by interpolating a third set of digital data defining image pixels at a third resolution finer than the first resolution but no finer than the second resolution, and thereafter replicating the third set of image data to obtain the second set.
Claim 6
Independent Claim
22 words
A method according to any of the preceding claims, wherein the interpolation is such as to enhance features in the reproduced image.
Claim 7
Dependent Claim
15 words
A method according to claim 5, wherein the interpolation is based on a cubic function.
Claim 8
Independent Claim
52 words
A method according to any of the preceding claims, wherein a pixel value (PV) is interpolated from the pixel values P₁₋P₄ of the neighbouring pixels of the first set in accordance with the formula: PV = AP₁ + BP₂ + CP₃ + DP₄ where A-D are weighting coefficients and A+B+C+D = 1.
Claim 9
Independent Claim
27 words
A method according to any of the preceding claims, wherein the record medium is exposed to a radiation beam modulated in response to the control signal (CS).
Claim 10
Dependent Claim
167 words
Apparatus for generating a half-tone version of an image represented by a first set of digital data defining the colour content of abutting pixels of the image at a first resolution, the apparatus comprising recording means (8); a record medium support (11), wherein the recording means and the support are relatively moveable such that an image can be recorded on a record medium (10) mounted on the support in a series of abutting scan lines; and a control signal generator (5) for generating a control signal (CS) representing image pixels at a second, finer resolution, which is fed to the recording means (8) such that a record medium on the support (11) is selectively exposed at the second, finer resolution, the control signal generator (5) being adapted to generate the control signal by comparing the second set of digital data with half-tone information, characterised in that the control signal generator at least partly interpolates the second set of digital data from the first set of digital data.
Claim 11
Dependent Claim
167 words
Apparatus for generating a half-tone version of an image represented by a first set of digital data defining the colour content of abutting pixels of the image at a first resolution, the apparatus comprising recording means (8); a record medium support (11), wherein the recording means and the support are relatively moveable such that an image can be recorded on a record medium (10) mounted on the support in a series of abutting scan lines; and a control signal generator (5) for generating a control signal (CS) representing image pixels at a second, finer resolution, which is fed to the recording means (8) such that a record medium on the support (11) is selectively exposed at the second, finer resolution, the control signal generator (5) being adapted to generate the control signal by comparing the second set of digital data with half-tone information, characterised in that the control signal generator at least partly interpolates the second set of digital data from the first set of digital data.
Claim 12
Dependent Claim
59 words
Apparatus according to claim 9, wherein the second set of digital data is obtained from the first set by interpolating a third set of digital data defining image pixels at a third resolution finer than the first resolution but no finer than the second resolution, and thereafter replicating the third set of image data to obtain the second set.
References Cited (Backward Citations)
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