EP0406956A1
Expired / Lapsed
EP
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A method of reproducing image information in vector form on to a raster pattern and apparatus for reproducing an image
Assignee: Canon Production Printing Netherlands BV
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Filing: 1990-06-29
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Granted: —
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Expires: 2010-06-29
Abstract
Abstract Boundaries between coloured and uncoloured image parts are reproduced on a pixel raster by determining a binary value ("coloured" or "uncoloured"), proceeding along a boundary, for adjoining pixels intersected by said boundary, said value being determined on the basis of the situation of said pixel with respect to the boundary and a carried-forward correction value. On the basis of the situation of said pixel with respect to the boundary a fractional value is calculated which is then rounded off to a binary pixel value. The rounding-off error made in such cases is processed using a prevention function for preventing allocating such binary values to the boundary pixels that visible bulges are formed on the boundary and is then carried forward to the next pixel and included in the fractional value thereof. Instances of such prevention functions are described. This procedure gives a better reproduction of lines extending obliquely over the pixel raster.
Inventors
- 👤 Maurice Lambert Martin Luttmer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 13:48
CPC Classifications
G; G06; G06K; G06K15/00; G06K15/02; G06K15/12; G06K15/128; G06K2215/00; G06K2215/0002; G06K2215/004; G06K2215/0042; G06K2215/0045; G06K2215/006
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
173 words
A method of reproducing image information in vector form on to a raster pattern of binary pixels, comprising allocating binary values to the pixels in dependence on the position of the said pixels with respect to coloured and uncoloured image areas contained in the image information, characterised in that pixels intersected by a boundary line between image areas are processed successively, following that boundary line, by allocating to each pixel a binary value in accordance with the sum of the ratio of the parts into which that pixel is divided by the boundary line and a correction value calculated from any error made by allocating a binary value to the previously processed pixel, the correction value being calculated by processing the said error made by allocating a binary value to the previously processed pixel with a prevention function for preventing allocating such binary values to pixels that those pixels form bulges on the boundary of a reproduced image area that are separated from each other by more than a predetermined number of pixels.
Claim 2
Independent Claim
173 words
A method of reproducing image information in vector form on to a raster pattern of binary pixels, comprising allocating binary values to the pixels in dependence on the position of the said pixels with respect to coloured and uncoloured image areas contained in the image information, characterised in that pixels intersected by a boundary line between image areas are processed successively, following that boundary line, by allocating to each pixel a binary value in accordance with the sum of the ratio of the parts into which that pixel is divided by the boundary line and a correction value calculated from any error made by allocating a binary value to the previously processed pixel, the correction value being calculated by processing the said error made by allocating a binary value to the previously processed pixel with a prevention function for preventing allocating such binary values to pixels that those pixels form bulges on the boundary of a reproduced image area that are separated from each other by more than a predetermined number of pixels.
Claim 3
Dependent Claim
64 words
A method according to claim 1, wherein the prevention function is given by f(err) = [err]n, wherein f is the prevention function; err is the error made by allocating a binary value to the previously processed pixel (expressed as a part of a pixel); [x]n means rounding off x to a whole multiple of 1/n (including 0), n is a predetermined integer > 1.
Claim 4
Dependent Claim
58 words
A method according to claim 1, wherein the prevention function is given by: f(err) = 0 if|err| < 1/n err if|err| >= 1/n, wherein f is the prevention function; err is the error made by allocating a binary value to the previously processed pixel (expressed as a part of a pixel); n is a predetermined integer > 1.
Claim 5
Dependent Claim
58 words
A method according to claim 1, wherein the prevention function is given by: f(err) = 0 when processing every (n-1)th pixel err otherwise, wherein f is the prevention function; err is the error made by allocating a binary value to the previously processed pixel (expressed as a part of a pixel); n is a predetermined integer > 2.
Claim 6
Dependent Claim
12 words
A method according to claim 2 or 3, wherein n = 2.
Claim 7
Dependent Claim
13 words
A method according to claim 2, 3 or 4, wherein n = 3.
Claim 8
Dependent Claim
181 words
Apparatus for reproducing image information in vector form, comprising a raster generator for allocating binary values to the pixels of a raster pattern in dependence on the position of the said pixels with respect to coloured and uncoloured image areas contained in the image information, characterised in that the raster generator is provided with - means for indicating successive adjoining pixels intersected by a boundary line between image areas; - means for allocating to an indicated pixel a binary value in accordance with the sum of the ratio of the parts into which that pixel is divided by the boundary line and a correction value; - means for calculating the error made by allocating a binary value to a pixel; - means for calculating a correction value by processing the error made by allocating a binary value to the previously indicated pixel with a prevention function for preventing allocating such binary values to pixels that those pixels form bulges on the boundary of a reproduced image area that are separated from each other by more than a predetermined number of pixels.
Claim 9
Dependent Claim
181 words
Apparatus for reproducing image information in vector form, comprising a raster generator for allocating binary values to the pixels of a raster pattern in dependence on the position of the said pixels with respect to coloured and uncoloured image areas contained in the image information, characterised in that the raster generator is provided with - means for indicating successive adjoining pixels intersected by a boundary line between image areas; - means for allocating to an indicated pixel a binary value in accordance with the sum of the ratio of the parts into which that pixel is divided by the boundary line and a correction value; - means for calculating the error made by allocating a binary value to a pixel; - means for calculating a correction value by processing the error made by allocating a binary value to the previously indicated pixel with a prevention function for preventing allocating such binary values to pixels that those pixels form bulges on the boundary of a reproduced image area that are separated from each other by more than a predetermined number of pixels.
Claim 10
Dependent Claim
45 words
Apparatus according to claim 7, wherein the means for calculating a correction value comprise a prevention function module that upon input of a value returns that value rounded off to a whole multiple of 1/n (including zero) (wherein n is a predetermined integer > 1).
Claim 11
Dependent Claim
62 words
Apparatus according to claim 7, wherein the means for calculating a correction value comprise a prevention function module that upon input of a value returns: - that same value, if the absolute value of that value is greater than or equal to 1/n, and - zero, if that absolute value is less than 1/n (wherein n is a predetermined integer > 1).
Claim 12
Dependent Claim
46 words
Apparatus according to claim 7, wherein tne means for calculating a correction value comprise a prevention function module that upon input of a value returns: - zero, when processing every (n-1)th pixel, and - that same value, otherwise (wherein n is a predetermined integer > 2).
Claim 13
Dependent Claim
11 words
Apparatus according to claim 8 or 9, wherein n = 2.
Claim 14
Dependent Claim
12 words
Apparatus according to claim 8, 9 or 10, wherein n = 3.
Claim 15
Dependent Claim
16 words
Raster generator for use in an apparatus according to any one of claims 7 to 12.
References Cited (Backward Citations)
US4593278A
Cited
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