Image-data processing apparatus
First Claim
1. An image-data processing apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data comprising a number of sets of multilevel pixel data each set of which represents one of more than two color values as a first color value indicating a color of a corresponding one of a number of pixels of the half-tone image, and is processed into a corresponding one of a number of sets of bilevel pixel data of the bilevel image data so that said corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of a number of pixels of the bilevel image, the apparatus comprising:
- data obtaining means for obtaining said multilevel image data; and
data processing means for processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data is distributed to at least one first pixel which neighbors said corresponding one pixel of the half-tone image and corresponds to at least one set of multilevel pixel data yet to be processed by said data processing means, said data processing means processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by employing a threshold value which is variable depending upon said each set of multilevel pixel data,wherein said data processing means comprises threshold determining means for determining said variable threshold value based on said each set of multilevel pixel data, andwherein said threshold determining means comprises means for determining said variable threshold value, Tvar, according to a following expression;
space="preserve" listing-type="equation">T.sub.var =a×
I+bwhere I is said first color value of said each set of multilevel pixel data, anda and b are predetermined values, respectively.
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Abstract
An apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data including sets of multilevel pixel data each set of which represents one of three or more color values as a first color value indicating a color of a corresponding one of pixels of the half-tone image, and is processed into a corresponding one of sets of bilevel pixel data of the bilevel image data so that the corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of pixels of the bilevel image, the apparatus including a data processing device for processing each set of multilevel pixel data into a corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing each set of multilevel pixel data into a corresponding one set of bilevel pixel data is distributed to one or more first pixels which neighbor the corresponding one pixel of the half-tone image and correspond to one or more sets of multilevel pixel data yet to be processed, the processing device processing each set of multilevel pixel data into a corresponding one set of bilevel pixel data, by employing a threshold value which is variable depending upon the each set of multilevel pixel data.
20 Citations
42 Claims
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1. An image-data processing apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data comprising a number of sets of multilevel pixel data each set of which represents one of more than two color values as a first color value indicating a color of a corresponding one of a number of pixels of the half-tone image, and is processed into a corresponding one of a number of sets of bilevel pixel data of the bilevel image data so that said corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of a number of pixels of the bilevel image, the apparatus comprising:
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data obtaining means for obtaining said multilevel image data; and data processing means for processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data is distributed to at least one first pixel which neighbors said corresponding one pixel of the half-tone image and corresponds to at least one set of multilevel pixel data yet to be processed by said data processing means, said data processing means processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by employing a threshold value which is variable depending upon said each set of multilevel pixel data, wherein said data processing means comprises threshold determining means for determining said variable threshold value based on said each set of multilevel pixel data, and wherein said threshold determining means comprises means for determining said variable threshold value, Tvar, according to a following expression;
space="preserve" listing-type="equation">T.sub.var =a×
I+bwhere I is said first color value of said each set of multilevel pixel data, and a and b are predetermined values, respectively.
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2. An image-data processing apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data comprising a number of sets of multilevel pixel data each set of which represents one of more than two color values as a first color value indicating a color of a corresponding one of a number of pixels of the half-tone image, and is processed into a corresponding one of a number of sets of bilevel pixel data of the bilevel image data so that said corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of a number of pixels of the bilevel image, the apparatus comprising:
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data obtaining means for obtaining said multilevel image data; and data processing means for processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data is distributed to at least one first pixel which neighbors said corresponding one pixel of the half-tone image and corresponds to at least one set of multilevel pixel data yet to be processed by said data processing means, said data processing means processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by employing a threshold value which is variable depending upon said each set of multilevel pixel data, wherein said data processing means comprises threshold determining means for determining said variable threshold value based on said each set of multilevel pixel data, and wherein said threshold determining means comprises means for determining said threshold value, Tvar, according to a following expression;
space="preserve" listing-type="equation">T.sub.var =n/2+(I-n/2)×
Awhere I is said first color value of said each set of multilevel pixel data, n is a number of said more than two color values, and A is an arbitrary coefficient satisfying 0<
A≦
1.
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3. An image-data processing apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data comprising a number of sets of multilevel pixel data each set of which represents one of more than two color values as a first color value indicating a color of a corresponding one of a number of pixels of the half-tone image, and is processed into a corresponding one of a number of sets of bilevel pixel data of the bilevel image data so that said corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of a number of pixels of the bilevel image, the apparatus comprising:
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data obtaining means for obtaining said multilevel image data; and data processing means for processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data is distributed to at least one first pixel which neighbors said corresponding one pixel of the half-tone image and corresponds to at least one set of multilevel pixel data yet to be processed by said data processing means, said data processing means processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by employing a threshold value which is variable depending upon said each set of multilevel pixel data, wherein said data processing means comprises threshold determining means for determining said variable threshold value base don said each set of multilevel pixel data, and wherein said threshold determining means comprises means for determining said threshold value, Tvar, according to a following expression;
space="preserve" listing-type="equation">T.sub.var =n/2+(I-n/2)×
1/2wherein I is said first color of each set of multilevel pixel data, and n is a number of said more than two color values.
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4. An image-data processing apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data comprising a number of sets of multilevel pixel data each set of which represents one of more than two color values as a first color value indicating a color of a corresponding one of a number of pixels of the half-tone image, and is processed into a corresponding one of a number of sets of bilevel pixel data of the bilevel image data so that said corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of a number of pixels of the bilevel image, the apparatus comprising:
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data obtaining means for obtaining said multilevel image data; and data processing means for processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data is distributed to at least one first pixel which neighbors said corresponding one pixel of the half-tone image and corresponds to at least one set of multilevel pixel data yet to be processed by said data processing means, said data processing means processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by employing a threshold value which is variable depending upon said each set of multilevel pixel data, wherein said data processing means comprises means for employing said variable threshold value when said first color value falls within a first range of said more than two color values, and employing, in place of said variable threshold value, a predetermined threshold value when said first color value falls within a second range of said more than two color values which does not overlap said first range. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An image-data processing apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data comprising a number of sets of multilevel pixel data each set of which represents one of more than two color values as a first color value indicating a color of a corresponding one of a number of pixels of the half-tone image, and is processed into a corresponding one of a number of sets of bilevel pixel data of the bilevel image data so that said corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of a number of pixels of the bilevel image, the apparatus comprising:
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data obtaining means for obtaining said multilevel image data; and data processing means for processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data is distributed to at least one first pixel which neighbors said corresponding one pixel of the half-tone image and corresponds to at least one set of multilevel pixel data yet to be processed by said data processing means, said data processing means processing, according to a predetermined rule, said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by using a first-color-value correction value having an absolute value greater than an absolute value of a sum of at least one error value distributed thereby to said corresponding one pixel of the half-tone image from at least one second pixel which neighbors said corresponding one pixel of the half-tone image and which corresponds to at least one set of multilevel pixel data which has been processed by the data processing means. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. An image-data processing apparatus for processing multilevel image data representing a half-tone image, into bilevel image data representing a bilevel image corresponding to the half-tone image, the multilevel image data comprising a number of sets of multilevel pixel data each set of which represents one of more than two color values as a first color value indicating a color of a corresponding one of a number of pixels of the half-tone image, and is processed into a corresponding one of a number of sets of bilevel pixel data of the bilevel image data so that said corresponding one set of bilevel pixel data represents one of two color values as a second color value indicating a color of a corresponding one of a number of pixels of the bilevel image, the apparatus comprising:
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data obtaining means for obtaining said multilevel image data; and data processing means for processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data, by an error diffusion process wherein an error value occurring in processing said each set of multilevel pixel data into said corresponding one set of bilevel pixel data is distributed to at least one first pixel which neighbors said corresponding one pixel of the half-tone image and corresponds to at least one set of multilevel pixel data yet to be processed by said data processing means, said data processing means determining, according to a predetermined rule, said error value by using a first-color-value correction value having an absolute value smaller than an absolute value of a sum of at least one error value distributed thereby to said corresponding one pixel of the half-tone image from at least one second pixel which neighbors said corresponding one pixel of the half-tone image and which corresponds to at least one set of multilevel pixel data which has been processed by the data processing means. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42)
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Specification