Multi-step-digital color image reproducing method and apparatus

• US 4,974,067 A
• Filed: 06/05/1987
• Issued: 11/27/1990
• Est. Priority Date: 06/06/1986
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Suzuki, Koichi, Murayama, Noboru
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Powell, Mark R.
• Application Number:
  US07/058,945
• Time in Patent Office: 1,271 Days
• Field of Search: 358/75, 358/75 IJ, 358/283, 358/80, 358/458, 358/459
• US Class Current: 358/534
• CPC Class Codes: H04N 1/4055 producing a clustered dots or a size modulated halftone pattern
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening

Abstract

A digital image processing method and an apparatus for the same which separate an original image into a plurality of color components to thereby produce image data each being associated with a respective one of the color components. The image data are individually processed to provide record color component density data. One halftone representation pattern is specified on a color component basis by the record color component density data to record that pattern. In color-by-color halftone data processing, there are used halftone representation patterns which are different in the positions of tone rendering spots from one color to another. Each of the record density data is extracted by assigning a particular area of the pattern thereto. The halftone representation patterns adapted to record a first and a second color which degrade color reproducibility when mixed together, e.g., those for magenta and cyan are provided with the centers of the above-mentioned spots at different positions from each other. The halftone representation patterns for recording a third color such as yellow have spots the centers of which are distributed between those of the patterns adapted for the first and second colors. The methodology and apparatus provide for the suppressing of overlapping of colors in a low density range despite the use of the same density pattern by changing the pattern phase, color by color and in addition implementing variable magnification recording of a high quality color image by use of a submatrix type recording system.

Claims

1. A digital processing method for reproduction of a color image comprising the steps of:

separating a color image into a plurality of color components;

converting image density into digital data on a color component basis;

processing said digital data to produce color component record density data;

specifying on a color basis and based on said color component record density data, one of a plurality of halftone representation patterns, each of which has a predetermined number of data bits and further wherein record data bits and non-record data bits, form said predetermined number of data bits wherein each of said bits correspond to a respective recording density, which are representative of the entire image;

setting up on a color basis a correspondence between data bits of one of said specified halftone representation patterns that represent a predetermined small area of a recording medium, said small area being divided into a plurality of minute subareas;

recording for a predetermined color in each minute subarea of said small area to which, among the data bits which correspond to the small area a given record data bit is assigned which represents said color;

assigning a group of plurality of halftone representation patterns to each of the color components, with each of said halftone representation patterns in the same group having a distribution of record data bit which is such that, when said halftone representation pattern is provided in a two-dimensional, or X-Y, bit distribution, record data bits sequentially expand from a predetermined point of X-Y coordinates as record density increases with said predetermined point of X-Y coordinates differing from one group to another;

specifying one of the halftone representation patterns, which correspond to any of the color components based on color component record density data of said color component, at least a part of said halftone representation pattern specified being extracted; and

assigning said color component, being recorded by said extracted part of said halftone representation pattern to a predetermined small area of a recording medium which is assigned to said color component record density data;

wherein assuming that each of the halftone representation patterns MMP is divided into m parts in a main scanning direction and n parts in a subscanning direction, i.e., into m×

n submatrix pattern where CMP₁₁ to CMP_mn are formed, where the former half of each subscript is representative of a position of the submatrix pattern in the halftone representation pattern MMP in the main scanning direction and the latter half of each subscript is representative of a position of said submatrix pattern in the subscanning direction, that said halftone representation pattern may be expressed as;

##EQU6## and that one halftone representation pattern of image data is defined by m×

n record density data such that ##EQU7## which is made up of the components ICD₁₁ to ICD_mn in the summation, with data in the submatrix pattern CMP_ij of the halftone representation pattern which is specified by the record density data ICD_ij being produced as record data in a bit distribution corresponding to said record density data ICD_ij.

2. A digital color image reproducing apparatus, comprising:

color image reading means for separating a color image into a plurality of color components and then converting image density into digital data on a color components basis;

color component digital data processing means for processing said digital data into color components record density data;

memory means for storing a plurality of groups of data which represent a plurality of halftone representation pattern data in each of which has record data bits and non-record bits which are distributed in correspondence with a respective one of record densities, which are to be representative of a given area, wherein each of said groups are assigned to a respective one of the color components, with each of the halftone representation pattern data in the same group, when distributed in a two-dimensional, or X-Y, bit distribution define a record area such that the record data bits sequentially expand from a predetermined point with respect to the X-Y coordinates with the record density increasing, and with said predetermined point of X-Y coordinates differing from one group to another;

pattern data reading means, for specifying one of the groups on a color components basis, wherein the specified one of said halftone representation pattern data, of said one group is based on the corresponding color component record density data, and reading data of a predetermined part of said one halftone representation pattern data specified out of said memory means; and

recording means for assigning said data in said predetermined part to a predetermined small area of a recording medium said small area being divided into a plurality of minute subareas, and recording a predetermined color in each minute subarea of said predetermined area to which record information bits in said data are to be assigned;

wherein assuming that each of the halftone representation patterns MMP is divided into m parts in a main scanning direction and n parts in a subscanning direction, i.e., into m×

n submatrix pattern where CMP₁₁ to CMP_mn are formed, where the former half of each subscript is representative of a position of the submatrix pattern in the halftone representation pattern MMP in the main scanning direction and the latter half of each subscript is representative of a position of said submatrix pattern in the subscanning direction, such that said halftone representation pattern may be expressed as;

##EQU8## and that one halftone representation pattern of image data is defined by m×

n record density data such that ##EQU9## which is made up of the components ICD₁₁ to ICD_mn, in the summation, where the pattern data of the submatrix pattern CMP_ij of the halftone representation pattern is specified by the record density data ICD_ij being produced as record data in a bit distribution corresponding to said record density data ICD_ij.

3. A digital processing method for reproducing a color image, comprising the steps of:

separating a color image into a plurality of color components;

converting image density into digital data on a color component basis to convert said digital data into color component record density data;

converting said color component record density data into record and non-record data bits by using a halftone representation pattern having a predetermined small area, said small area being divided into a plurality of minute subareas, in which a plurality of threshold data are provided in one-to-one correspondence with predetermined minute subareas, or halftone representation patterns constituted by a plurality of data bit distribution patterns, a number of which corresponds to a predetermined range of record density data, in which record and non-record bits are distributed in correspondence with said small area by comparing all of threshold data with said record density data; and

assigning record and non-record bit data to a minute area of a recording medium on a color component basis, and recording a predetermined color in a minute area to which, among the bit data assigned to said first-mentioned minute subarea, the record data bits are to be assigned;

a plurality of groups of the halftone representation patterns are provided one for a respective one of the color components, each of said halftone representation patterns adapted for at least first color and second color recording having a record data bit distribution which is such that, when said halftone representation patterns is used for recording a predetermined area, record information bits sequentially expand from a predetermined point of X-Y coordinates, a plurality of said predetermined points of X-Y coordinates being scattered in particular positions which differ from one color components to another;

wherein assuming that each of the halftone representation patterns MMP is divided into m parts in a main scanning direction and n parts in a subscanning direction, i.e., into m×

n submatrix pattern where CMP₁₁ to CMP_mn are formed, where the former half of each subscript is representative of a position of the submatrix pattern in the halftone representation pattern MMP in the main scanning direction and the latter half of each subscript is representative of a position of said submatrix pattern in the subscanning direction, that said halftone representation pattern may be expressed as;

##EQU10## and that one halftone representation pattern of image data is defined by m×

n record density data such that ##EQU11## which is made up of the components ICD₁₁ to ICD_mn in the summation, with the pattern data of the submatrix pattern CMP_ij of the halftone representation pattern being specified, by the record density data ICD_ij, which is produced as record data in a bit distribution corresponding to said record density data ICD_ij.

4. A method as claimed in claim 3 wherein minute subareas a number of which corresponds to a part of the halftone representation pattern are recorded assigned one to each color record density data.

5. A method as claimed in claim 3, wherein while the halftone representation patterns adapted for the first color and second color recording become substantially analogous in pattern when many of each said halftone representation pattern are developed in a plane, threshold data or record and non-record data are distributed such that the predetermined points associated with the first recording and those associated with the second recording are distributed at the furthest point from each other and the distance between these if plotted on an X-Y coordinate system are at the maximum distance from each other.

6. A digital color image reproducing apparatus, comprising:

color image reading means for separating a color image into a plurality of color components and, then, converting image density into digital data on a color component basis;

color component data processing means for processing said digital data into color components record density data;

memory means storing a plurality of groups of a plurality of halftone representation pattern data in each of which print data bit and non-print data bit are distributed in correspondence with a respective one of record densities, which are to be rendered as a certain entire area, each of said groups being assigned to a respective one of the color components, each of the halftone representation pattern data in the same group, when distributed in a two-dimensional, or X-Y, bit distribution which defines a record area, being such that the record data bits sequentially expand from a predetermined point of X-Y coordinates as the record density is increased, a plurality of said predetermined points being distributed in positions which differ from group to group;

pattern data reading means for specifying one of the groups on a color components basis, specifying one halftone representation pattern data of said one group based on the color component record density data, and reading data of a predetermined area of said one halftone representation pattern data specified out of said memory means; and

recording means for assigning said data in said predetermined area to a predetermined small area of a recording medium, and recording a predetermined color in a minute subarea of said predetermined area to which record data bits in said data are to be assigned;

wherein assuming that each of the halftone representation patterns MMP is divided into m parts in a main scanning direction and n parts in a subscanning direction, i.e., into m×

n submatrix pattern where CMP₁₁ to CMP_mn are formed, where the former half of each subscript is representative of a position of the submatrix pattern in the halftone representation pattern MMP in the main scanning direction and the latter half of each subscript is representative of a position of said submatrix pattern in the subscanning direction, that said halftone representation pattern may be expressed as;

##EQU12## and that one halftone representation pattern of image data is provided by m×

n record density data ##EQU13## which is made up of the components ICD₁₁ to ICD_mn, in the summation, with the pattern data in the submatrix pattern CMP_ij of the halftone representation pattern which is specified by the record density data ICD_ij being produced as record data in a bit distribution corresponding to said record density data ICD_ij.

7. In a digital processing method for reproducing a color image, having the steps of separating a color image into a plurality of color component, and converting image density into digital data on a color component basis to convert said digital data into color component record density data;

converting said color component record density data into record an non-record bit data by using a halftone representation pattern having a predetermined small area in which a plurality of threshold data are provided in one-to-one correspondence with predetermined minute subareas, or halftone representation patterns constituted by a plurality of bit distribution patterns, a number of which corresponds to a predetermined range of record density data, in which record and non-record bits are distributed in correspondence to said small area by comparing all of threshold data with said record density data; and

assigning record and non-record bit data to a minute area of recording medium on a color component basis, and recording a predetermined color in a minute area to which, among the bit data assigned to said first-mentioned minute subarea, the record data bits are to be assigned;

each of the halftone representation patterns adapted for first color and second color recording is such that, when said halftone representation pattern is used for recording a predetermined area, record information bits sequentially expand from a predetermined point of X-Y coordinates, said predetermined point of X-Y coordinates differing in position from one color to another, a halftone representation pattern for third color recording being different from those of the first color and second color recording in that record data bits expand from each of a plurality of predetermined points which are distributed between the predetermined points of the first color and second color recording;

wherein assuming that each of the halftone representation patterns MMP is divided into m parts in a main scanning direction and n parts in a subscanning direction, i.e., into m×

n submatrix pattern where CMP₁₁ to CMP_mn are formed, where the former half of each subscript is representative of a position of the submatrix pattern in the halftone representation pattern MMP in the main scanning direction and the latter half of each subscript is representative of a position of said submatrix pattern in the subscanning direction, such that said halftone representation pattern may be expressed as;

##EQU14## and that one halftone representation pattern of image information is defined by m×

n record density data such that ##EQU15## which is made up of the components ICD₁₁ to ICD_mn, in the summation, the pattern data of the submatrix pattern CMP_ij of the halftone representation pattern is specified by the record density data ICD_ij being produced as record data in a bit distribution corresponding to said record density data ICD_ij.

8. A method as claimed in claim 7, wherein minute subareas a number of which corresponds to a part of the halftone representation pattern are recorded assigned one to each color record density data.

9. A method as claimed in claim 7, wherein while the halftone representation patterns adapted for the first color and second color recording become substantially analogous in pattern when many of each said halftone representation pattern are developed in a plane, threshold data or record and non-record data are distributed such that the predetermined points associated with the first recording and those associated with the second recording are distributed at [a maximum distance if plotted on an X-Y system, from each other.]

10. A digital color reproducing apparatus comprising:

color image reading means for separating a color image into a plurality of color components and, then, converting image density into digital data on a color component basis;

color component data processing means for processing said digital data into color component record density data;

memory means storing halftone representation patterns of a first color recording group and halftone representation patterns of a second color recording group, each of said halftone representation patterns having a record data bit distribution which is such that record data bits sequentially expand from a predetermined point of X-Y coordinates as record density is increased, said predetermined point differing from one color to another, and halftone representation patterns of a third color recording group which are different from said halftone representation patterns for said first color and second color recording and each having a recording bit distribution which is such that record data bits expand from each of a plurality of predetermined points, which are distributed between the predetermined point of the first color and second color recording;

pattern data reading means for specifying one of the groups based on the color component, specifying one halftone representation pattern data of said one group based on the color component record density data, and reading data of a predetermined area of said halftone representation pattern data specified out of said memory means; and

recording means for assigning said data in said predetermined area to a predetermined small area of a recording medium, an recording a predetermined color in a minute subarea of said predetermined area to which record data bits in said data are to be assigned;

wherein assuming that each of the halftone representation patterns MMP is divided into m parts in a main scanning direction and n parts in a subscanning direction, i.e., into m×

n submatrix pattern where CMP₁₁ to CMP_mn are formed, where the former half of each subscript is representative of a position of the submatrix pattern in the halftone representation pattern MMP in the main scanning direction and the latter half of each subscript is representative of a position of said submatrix pattern in the subscanning direction, such that said halftone representation pattern may be expressed as;

##EQU16## and that one halftone representation pattern of image information is defined by m×

n record density data such that ##EQU17## which is made up of the components ICD₁₁ to ICD_mn, in the summation, where the pattern information data of the submatrix pattern CMP_ij of the halftone representation pattern is specified by the record density data ICD_ij being produced as record information in a bit distribution corresponding to said record density data ICD_ij.