EP0398763A2
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EP
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Image forming apparatus
Assignee: Canon Inc
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Filing: 1990-05-18
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Granted: —
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Expires: 2010-05-18
Abstract
Abstract An image forming apparatus for forming a color image from image data on an image having a plurality of colors. Density conversion information is stored with respect to pixel blocks having a predetermined phase and a predetermined configuration, which blocks are provided for each color. Pixel density values of image data items corresponding to each of the density conversion blocks are successively compared with a predetermined threshold value, and the compared image data item is converted according to the density conversion information if (pixel density) < (predetermined threshold value) is satisfied, thereby limiting changes in color tones at a highlighted portion of the image and stabilizing the color tones.
Inventors
- 👤 Kazuhisa C/O Canon Chigusadai-Ryo Kemmochi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 14:20
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/52; H04N1/40; H04N1/40087
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
153 words
An image forming apparatus comprising: input means for inputting image data on an image having a plurality of color elements; storage means for storing information on density conversion blocks having a predetermined phase and a predetermined configuration with respect to each color element; conversion means for comparing pixel density values of image data items corresponding to each of the density conversion blocks memorized by said storage means with a predetermined threshold value, and for converting the compared image data item in accordance with the density conversion information if (the pixel density) < (the predetermined threshold value) is satisfied; binary coding means for converting image data output from said conversion means into a binary signal corresponding to the density designated by this image data; and image forming means for forming a color image in which the plurality of color elements are superposed in accordance with the binary signals output from said binary coding means.
Claim 2
Dependent Claim
153 words
An image forming apparatus comprising: input means for inputting image data on an image having a plurality of color elements; storage means for storing information on density conversion blocks having a predetermined phase and a predetermined configuration with respect to each color element; conversion means for comparing pixel density values of image data items corresponding to each of the density conversion blocks memorized by said storage means with a predetermined threshold value, and for converting the compared image data item in accordance with the density conversion information if (the pixel density) < (the predetermined threshold value) is satisfied; binary coding means for converting image data output from said conversion means into a binary signal corresponding to the density designated by this image data; and image forming means for forming a color image in which the plurality of color elements are superposed in accordance with the binary signals output from said binary coding means.
Claim 3
Dependent Claim
38 words
An image forming apparatus according to claim 1, wherein said threshold value is set to a value not smaller than the minimum of pixel density levels at which image development can be effected by said image forming means.
Claim 4
Dependent Claim
19 words
An image forming apparatus according to claim 1, wherein said image data contains elements of yellow, magenta and cyan.
Claim 5
Dependent Claim
36 words
An image forming apparatus according to claim 1, wherein said conversion means includes comparing means for comparing said image data with said threshold value and adding means for adding image data of a plurality of pixels.
Claim 6
Dependent Claim
19 words
An image forming apparatus according to claim 1, wherein said binary coding means includes a pulse width modulation circuit.
Claim 7
Dependent Claim
19 words
An image forming apparatus according to claim 1, wherein said image forming means is a frame sequential color printer.
Claim 8
Dependent Claim
18 words
An image forming apparatus according to claim 6, wherein said image forming means is a laser beam printer.
Claim 9
Dependent Claim
15 words
An image forming apparatus according to claim 1, wherein said storage means is a table.
Claim 10
Dependent Claim
62 words
An image processing apparatus comprising: input means for inputting color image data corresponding to a given image; concentrating means for concentrating data less than a predetermined value from said color image data, said concentrating means concentrating said color image data corresponding to a kind of color elements; and supplying means for suppling data concentrated by said concentrating means to a color printer.
Claim 11
Dependent Claim
62 words
An image processing apparatus comprising: input means for inputting color image data corresponding to a given image; concentrating means for concentrating data less than a predetermined value from said color image data, said concentrating means concentrating said color image data corresponding to a kind of color elements; and supplying means for suppling data concentrated by said concentrating means to a color printer.
Claim 12
Dependent Claim
18 words
An image processing apparatus according to claim 9, wherein said color printer is a frame sequential color printer.
Claim 13
Dependent Claim
36 words
An image processing apparatus according to claim 9, wherein said concentrating means includes comparing means for comparing said image data with said threshold value and adding means for adding image data of a plurality of pixels.
Claim 14
Dependent Claim
39 words
An image processing apparatus according to claim 11, wherein said concentrating means concentrates said image data corresponding to the kind of color elements through changing order of additions by said adding means corresponding to the kind of color elements.
Claim 15
Dependent Claim
22 words
An image processing apparatus according to claim 9, wherein said concentrating means respectively executes different concentration to each kind of color elements.
Claim 16
Dependent Claim
22 words
An image processing apparatus according to claim 9, wherein said color image data includes elements of yellow, magenta and cyan image data.
Claim 17
Dependent Claim
38 words
An image processing apparatus according to claim 9, wherein said supplying means includes binary coding means for converting image data output from said concentrating means into a binary signal corresponding to the density designated by the image data.
Claim 18
Dependent Claim
19 words
An image processing apparatus according to claim 15, wherein said binary coding means includes a pulse width modulation circuit.
Claim 19
Dependent Claim
17 words
An image processing apparatus according to claim 10, wherein said color printer is a laser beam printer.
Claim 20
Dependent Claim
36 words
An image processing apparatus according to claim 9, wherein said concentrating means includes storage means for storing information on density conversion blocks having a predetermined phase and a predetermined configuration with respect to each color element.
Claim 21
Dependent Claim
15 words
An image processing apparatus according to claim 18, wherein said storage means is a table.
Claim 22
Independent Claim
234 words
A method or apparatus for forming an image having a first colour and a second colour, in which the first colour image is divided into a first predetermined pattern of blocks of pixels, and if a pixel in a block has an image value for the first colour which is below a first colour threshold value, the image values for the first colour in the block are redistributed amongst pixels according to predetermined rules which establish for each said block a priority pixel position in which image values for the first colour are preferentially accumulated, and in which the second colour image is divided into a second predetermined pattern of blocks of pixels, and if a pixel in a block has an image value for the second colour which is below a second colour threshold value, the image values for the second colour in the block are redistributed amongst pixels according to predetermined rules which establish for each block a priority pixel position in which image values for the second colour are preferentially accumulated, characterised in that the first and second predetermined patterns and the predetermined rules are such that the proportion of priority pixels of the first colour which are superposed on priority pixels of the second colour remains substantially constant for at least a one-pixel superposition error shift in a first direction between the first colour image and the second colour image.
Claim 23
Independent Claim
234 words
A method or apparatus for forming an image having a first colour and a second colour, in which the first colour image is divided into a first predetermined pattern of blocks of pixels, and if a pixel in a block has an image value for the first colour which is below a first colour threshold value, the image values for the first colour in the block are redistributed amongst pixels according to predetermined rules which establish for each said block a priority pixel position in which image values for the first colour are preferentially accumulated, and in which the second colour image is divided into a second predetermined pattern of blocks of pixels, and if a pixel in a block has an image value for the second colour which is below a second colour threshold value, the image values for the second colour in the block are redistributed amongst pixels according to predetermined rules which establish for each block a priority pixel position in which image values for the second colour are preferentially accumulated, characterised in that the first and second predetermined patterns and the predetermined rules are such that the proportion of priority pixels of the first colour which are superposed on priority pixels of the second colour remains substantially constant for at least a one-pixel superposition error shift in a first direction between the first colour image and the second colour image.
References Cited (Backward Citations)
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