Method of and apparatus for removing artifacts from a reproduction

Claim 1

A method of reducing aliasing effects in a reproduction of an original image wherein the reproduction is divided into a two-dimensional array of pixels and each pixel has a sampled value associated therewith representing any of a plurality of grayscale levels at an associated portion thereof, the sampled values being stored in a memory, the method comprising the steps of: programming a general purpose computer to access the memory and execute the program steps of: finding a first set of pixels extending in a first direction in the reproduction and satisfying a first condition indicating that an edge has been found; defining a number of second sets of pixels in the reproduction wherein each second set includes a pixel adjacent to a pixel of the first set and at least one additional pixel and wherein the pixels of each second set extend along a line transverse to the first direction; analyzing the first set of pixels and the pixels of the second sets of pixels to determine whether a second condition is met indicating that a stroke has been found; if the second condition is met identifying a third set of pixels extending in the first direction in the reproduction from the first set of pixels and from sampled values associated with the second set of pixels; an reducing the number of grayscale levels by modifying the sampled values for pixels of the third set toward a first value and modifying the sampled values for pixels adjacent pixels of the third set toward a second value.

Claim 2

A method of reducing aliasing effects in a reproduction of an original image wherein the reproduction is divided into a two-dimensional array of pixels and each pixel has a sampled value associated therewith representing any of a plurality of grayscale levels at an associated portion thereof, the sampled values being stored in a memory, the method comprising the steps of: programming a general purpose computer to access the memory and execute the program steps of: finding a first set of pixels extending in a first direction in the reproduction and satisfying a first condition indicating that an edge has been found; defining a number of second sets of pixels in the reproduction wherein each second set includes a pixel adjacent to a pixel of the first set and at least one additional pixel and wherein the pixels of each second set extend along a line transverse to the first direction; analyzing the first set of pixels and the pixels of the second sets of pixels to determine whether a second condition is met indicating that a stroke has been found; if the second condition is met identifying a third set of pixels extending in the first direction in the reproduction from the first set of pixels and from sampled values associated with the second set of pixels; an reducing the number of grayscale levels by modifying the sampled values for pixels of the third set toward a first value and modifying the sampled values for pixels adjacent pixels of the third set toward a second value.

Claim 12

A method of modifying an image having a plurality of pixels each of which has a sampled value stored in a memory associated therewith, and wherein each sampled value can assume a scale level the method comprising the steps of: programming a general purpose computer to access the memory and execute the program steps of finding pixels in the image satisfying an edge condition and extending in a first direction; determining from the found pixels the overall dimension of a stroke in a second direction transverse to the first direction; identifying a set of contiguous pixels defining a first line extending in the first direction in dependence upon the found pixels and the determined stroke dimension; and reducing the number of grayscale levels by modifying the sampled values for the pixels in the identified set toward a first value and modifying the sampled values for pixels defining a second line adjacent the first line toward a second value.

Claim 13

A method of modifying an image having a plurality of pixels each of which has a sampled value stored in a memory associated therewith, and wherein each sampled value can assume a scale level the method comprising the steps of: programming a general purpose computer to access the memory and execute the program steps of finding pixels in the image satisfying an edge condition and extending in a first direction; determining from the found pixels the overall dimension of a stroke in a second direction transverse to the first direction; identifying a set of contiguous pixels defining a first line extending in the first direction in dependence upon the found pixels and the determined stroke dimension; and reducing the number of grayscale levels by modifying the sampled values for the pixels in the identified set toward a first value and modifying the sampled values for pixels defining a second line adjacent the first line toward a second value.

Claim 19

A method of developing a halftone reproduction of an original image having a plurality of pixels each of which has a sampled value associated therewith wherein the sampled values are in a range between first and second limits, the method comprising the steps of: finding a first set of pixels extending in a first direction in the image and satisfying an edge condition; identifying a second set of pixels also extending in the first direction in the image and which, together with the first set of pixels, define a stroke; associating with each pixel of the first set a pixel of the second set wherein associated pixels of the first and second sets are displaced from one another along a second direction perpendicular to the first direction; for each pixel of the first set adding the sampled value thereof to the sampled value of the pixel of the second set associated therewith and the sampled values of all pixels located therebetween to obtain a plurality of sums; dividing each sum by one of the first and second limits to obtain a plurality of stroke run lengths each associated with one of the pixels of the first set; finding the most common stroke run length and the pixels of the first set associated with the most common run length; defining first and second lines extending in the first direction based upon the pixels of the first set associated with the most common stroke run length; converting pixels lying on the first and second lines to a first binary value; converting pixels on third and fourth lines adjacent to the first and second lines, respectively, to a second binary value; and using the binary values of the converted pixels to control a halftone reproduction device.

Claim 20

A method of developing a halftone reproduction of an original image having a plurality of pixels each of which has a sampled value associated therewith wherein the sampled values are in a range between first and second limits, the method comprising the steps of: finding a first set of pixels extending in a first direction in the image and satisfying an edge condition; identifying a second set of pixels also extending in the first direction in the image and which, together with the first set of pixels, define a stroke; associating with each pixel of the first set a pixel of the second set wherein associated pixels of the first and second sets are displaced from one another along a second direction perpendicular to the first direction; for each pixel of the first set adding the sampled value thereof to the sampled value of the pixel of the second set associated therewith and the sampled values of all pixels located therebetween to obtain a plurality of sums; dividing each sum by one of the first and second limits to obtain a plurality of stroke run lengths each associated with one of the pixels of the first set; finding the most common stroke run length and the pixels of the first set associated with the most common run length; defining first and second lines extending in the first direction based upon the pixels of the first set associated with the most common stroke run length; converting pixels lying on the first and second lines to a first binary value; converting pixels on third and fourth lines adjacent to the first and second lines, respectively, to a second binary value; and using the binary values of the converted pixels to control a halftone reproduction device.

Claim 24

A system for reducing aliasing effects in a reproduction of an original image wherein the reproduction is divided into a two-dimensional array of pixels and wherein each pixel has a sampled value associated therewith representing any of a plurality of grayscale levels at an associated portion thereof, comprising: a computer-readable memory for storing programming to implement means for finding a first set of pixels extending along a first direction in the reproduction and satisfying an edge condition; means for defining a number of second sets of pixels in the reproduction wherein each second set includes a pixel adjacent to a pixel of the first set and at least one additional pixel and wherein the pixels of each second set extend along a line transverse to the first direction; means for analyzing the first set of pixels and the pixels of the second sets of pixels to determine whether a second condition is met indicating that a stroke has been found; means coupled to the finding means for identifying a third set of pixels extending in the first direction in the reproduction from the first set of pixels and from sampled values associated with the second set of pixels; and means coupled to the identifying means for reducing the number of grayscale levels by modifying the sampled values for pixels of the third set toward a first value and by modifying the sampled values for pixels adjacent pixels of the third set toward a second value.

Claim 25

A system for reducing aliasing effects in a reproduction of an original image wherein the reproduction is divided into a two-dimensional array of pixels and wherein each pixel has a sampled value associated therewith representing any of a plurality of grayscale levels at an associated portion thereof, comprising: a computer-readable memory for storing programming to implement means for finding a first set of pixels extending along a first direction in the reproduction and satisfying an edge condition; means for defining a number of second sets of pixels in the reproduction wherein each second set includes a pixel adjacent to a pixel of the first set and at least one additional pixel and wherein the pixels of each second set extend along a line transverse to the first direction; means for analyzing the first set of pixels and the pixels of the second sets of pixels to determine whether a second condition is met indicating that a stroke has been found; means coupled to the finding means for identifying a third set of pixels extending in the first direction in the reproduction from the first set of pixels and from sampled values associated with the second set of pixels; and means coupled to the identifying means for reducing the number of grayscale levels by modifying the sampled values for pixels of the third set toward a first value and by modifying the sampled values for pixels adjacent pixels of the third set toward a second value.

Claim 35

A system for creating a halftone reproduction of an image having a plurality of pixels each of which has a grayscale sampled value associated therewith, comprising; means for finding a first set of pixels in the image extending in a first direction and satisfying an edge condition; means coupled to the finding means for determining from the first set of pixels the overall dimension of a stroke in a second direction transverse to the first direction; means coupled to the finding means and the determining means for identifying a set of contiguous pixels defining a first line extending in the first direction in dependence upon the pixels of the first set and the determined stroke dimension; means coupled to the identifying means for setting the sampled values for the pixels in the identified set equal to a first halftone value and for setting the sampled values for pixels defining a second line adjacent the first line equal to a second halftone value; and a halftone reproduction device coupled to the setting means for creating the halftone reproduction.

Claim 36

A system for creating a halftone reproduction of an image having a plurality of pixels each of which has a grayscale sampled value associated therewith, comprising; means for finding a first set of pixels in the image extending in a first direction and satisfying an edge condition; means coupled to the finding means for determining from the first set of pixels the overall dimension of a stroke in a second direction transverse to the first direction; means coupled to the finding means and the determining means for identifying a set of contiguous pixels defining a first line extending in the first direction in dependence upon the pixels of the first set and the determined stroke dimension; means coupled to the identifying means for setting the sampled values for the pixels in the identified set equal to a first halftone value and for setting the sampled values for pixels defining a second line adjacent the first line equal to a second halftone value; and a halftone reproduction device coupled to the setting means for creating the halftone reproduction.