JPH06105161A - Full color picture recorder - Google Patents

Abstract

PURPOSE:To obtain the full color picture recorder without a color difference and uneven color while attaining color reproduction with fidelity when an half tone picture is recorded by using a color laser printer 8. CONSTITUTION:Three primary color picture data R8, G8, B8 are converted into 3-primary color binary data R1, G1, B1 through binarization processing, the data R1, G1, B1 are stored tentatively in memories 2, 3, 4, and read from the memories 2, 3, 4 to implement full color recording. In this case, the three primary color picture data R8, G8, B8 are subjected to vector processing at binarization processing, then error diffusion is implemented altogether. When a color difference is calculated between the picture element data and the three primary color picture data R1, G1, B1 and picture element data receiving a diffusion by the error diffusion, a weight coefficient is multiplied with a color difference to control the correlation coefficient among the three primary color picture data R1, G1, B1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-color image recording apparatus, and more particularly, to digital full-color image data.
In order to obtain the binary data suitable for the recording apparatus by controlling the value of the correlation coefficient of the binary data of the three primary colors during the binarization process of compressing the binary data into the binary data of the three primary colors. Full-color image recording device.

[0002]

2. Description of the Related Art In an office or the like, a large amount of documents are always stored in a memory device such as a large-capacity optical disk,
A system that retrieves a desired document from the large number of documents and prints it out as needed is usually called an electronic filing system. It is widely used in recent years because it can significantly improve the utilization efficiency of space such as offices.

FIG. 10 is a block diagram showing an example of a schematic configuration of the known electronic filing system, which is applied to a monochrome system.

In FIG. 10, reference numeral 80 is a document, 81 is an image scanner, 82 is an area determination device, and 83 is a character area 2.
Quantizer, 84 halftone area binarizer, 85 selector, 86 temporary image memory device, 87 optical disk, 8
Reference numeral 8 is a laser printer, and 89 is a duplicate recording original.

The area determining device 82, the character area binarizing device 83, the halftone area binarizing device 84, and the selector 85.
Constitutes the binarization processing means 90 as a whole.

The known electronic filing system configured as described above operates as described below.

First, the image scanner 81 uses the document 8
Scanning reading of 0 is performed, and 8-bit data K8 indicating the reflection density of each pixel is generated. Next, the 8-bit data K8 is supplied to the binarization processing means 90. At this time, in the area determination device 82, the read portion of the document 80 is a character area based on the 8-bit data K8. Or it is in the halftone region. When it is determined in the above determination that the area is the character area, a threshold is provided between the background density and the character density in the character area binarizing device 83, and the 8-bit data K8 is converted into 1-bit binary data. On the other hand, when it is determined in the determination that it is a halftone region, the halftone region binarizing device 84 uses the pseudo-halftone representation such as the error diffusion method to the 8-bit data K8. Is compressed into binary data K1. Furthermore, selector 8
5 selects one binary data K1 from the two binary data K1 based on the result of the determination made by the area determination device 82, and the selected binary data K1 is binarized 90. To output from.

Subsequently, the binary data K1 output from the binarization processing means 90 is sent to the temporary image memory device 86 and temporarily stored therein, and then the optical disk 8 is stored.
7 for storage and storage there for an appropriate period. On the other hand, when searching for a required document from many documents,
The binary data K1 corresponding to the required document is called from the optical disc 87 into the temporary image memory device 86, and the user confirms the contents of the binary data K1 and then prints it on the recording paper by using the laser printer 88 or the like. Value recording,
A duplicate recording original 89 is obtained. In this case, although the copied recording original 89 is binary recording, pseudo halftone is expressed in the halftone area by the above-mentioned error diffusion method or the like.

Next, FIG. 9 is a block diagram showing another example of a schematic configuration of the known electronic filing system, which is applied to a full color system.

In FIG. 9, 60 is a full-color original, 6
1 is a full color image scanner, 62 is for red (R) 2
Binarization processing means, 63 is green (G) binarization processing means, 64
Is a binarization processing unit for blue (B), 65 is a temporary image memory device for red (R), 66 is a temporary image memory device for green (G),
67 is a temporary image memory device for blue (B), 68 is an optical disk, 69 is a full-color laser printer, and 70 is a duplicated full-color recording original.

The full color electronic filing system operates as described below. First, the full-color image scanner 61 scans and reads the full-color original 60, and 8-bit data R of three primary colors of red (R), green (G), and blue (B) color-separated for each pixel.
8, G8 and B8 are generated. Next, 8 of the three primary colors
The bit data R8, G8, B8 are binarized by the binarization processing means 62, 63, 64 dedicated to each color,
1-bit binary data R1, G1, B corresponding to three primary colors
Converted to 1. Next, these binary data R1 and G
1 and B1 are transferred to the optical disc 68 via the temporary image memory devices 65, 66 and 67 respectively dedicated to the three primary colors, and stored and stored in the optical disc 68 for an appropriate period. On the other hand, among a large number of documents stored in the optical disc 68, a required document is read from the optical disc 68 and supplied to each of the temporary image memory devices 65, 66 and 67, where the user confirms the document. After that, the document is supplied to a full-color laser printer 69 or the like,
The duplicated full-color recording original 70 is obtained.

In this case, the data processing in the full-color electronic filing system is performed completely independently for each of the three primary colors of red (R), green (G), and blue (B). The image of the full-color original 60 is equivalently processed as a 3-page monochrome image. As described above, in the known full-color electronic filing system, the data processing is performed completely independently for each of the three primary colors. Therefore, in the known black-and-white electronic filing system, each color is processed three times (three colors). By performing the data processing, it becomes possible to realize a full-color image, and there is an advantage that the configuration is simple.

[0013]

However, the full-color laser printer 69 used in the known full-color electronic filing system is of a recording type which expresses a full-color image by superposing a plurality of color toners (solid state). Therefore, unlike the recording method using the printing ink (liquid state) and the like, the overlapping manner of the color toners is not constant, and the color developing property is largely changed, which is peculiar to the full-color laser printer 69. Becoming a phenomenon.

By the way, in the binarization processing means 62, 63 and 64 dedicated to the three primary colors used in the known full-color electronic filing system, consideration is given to the peculiar phenomenon in the recording system using the full-color laser printer 69. Is not paid at all. Therefore, in the known full-color electronic filing system, when the full-color recording is performed by the full-color laser printer 69, the overlapping manner of the color toners is not constant, and the coloring property of the toner is largely changed, so that the copied full-color recording original 70 is , The color of the halftone recorded image is significantly different from the color of the full-color original, or color unevenness becomes noticeable, and as a result, a high-quality and high-fidelity recorded image cannot be obtained. There is a problem.

The present invention eliminates the above-mentioned problems, and an object thereof is to achieve faithful color reproduction without color difference or color unevenness when recording an image in a halftone using a full-color laser printer. It is to provide a possible full-color image recording device.

Another object of the present invention is to provide a full-color image recording apparatus capable of appropriately changing the image quality of a halftone recorded image by positively changing the color forming property of a full-color laser printer.

[0017]

In order to achieve the above object, the present invention converts three primary color data of a full color image into three primary color binary data by a binarization process, and the three primary color 2
In a full-color image recording device that temporarily stores value data in a memory and then reads out from the memory for full-color recording, during the binarization processing, three primary color image data obtained from the full-color image are vectorized and then collectively processed. When the error diffusion is performed and the color difference between the pixel data to which the diffusion error is added by the error diffusion and the binary data of the three primary colors is calculated, the color difference is multiplied by the weighting coefficient,
The first means is provided for controlling the value of the correlation coefficient of the binary data of the three primary colors.

Further, in order to achieve the above-mentioned other object, the present invention provides a color laser printer in which cyan (C),
When recording with the three primary colors of magenta (M) and yellow (Y), control is performed so that the value of the correlation coefficient of the three-primary-color binary data becomes small, while cyan (C), magenta (M), When recording is performed by removing the undercolor by adding black (B) in addition to the three primary colors of yellow (Y), it is controlled to increase the value of the correlation coefficient of the three primary color binary data. Means are provided.

Further, in order to achieve the above-mentioned other object, the present invention comprises third means capable of manually controlling the value of the correlation coefficient of the binary data of the three primary colors.

[0020]

According to the first means, the 8-bit 3-primary color image data R8, G8, B8 are vectorized and then error diffusion is carried out collectively. If the data R8, G8, and B8 are used as vector quantities to perform binarization at one time, theoretically, at the time of conversion into the three primary color binary data R1, G1, and B1 by the error diffusion,
It is possible to increase or decrease the correlation characteristic between the three primary color binary data R1, G1, and B1 without changing the reproduced color.

Here, if the correlation characteristic is high, the overlapping portion of the three primary color binary data R1, G1, B1 is large, and conversely, if the correlation characteristic is low, the
The overlapping portion of the primary color binary data R1, G1, B1 is reduced.

Further, according to the first means, when the color difference between the pixel data to which the diffusion error is added and the binary data of the three primary colors is calculated, the color difference is multiplied by the weighting coefficient. ing. When the color difference is multiplied by the weighting coefficient, the three primary color binary data R1, G1, B
Among 8 colors of white (W), black (K), red (R), green (G), blue (B), cyan (C), magenta (M), and yellow (Y) reproduced by 1. For example, if the weighting coefficient by which the color difference of white (W) and black (K) is multiplied is selected to be small, the reproduction ratio of white (W) or black (K) increases due to error diffusion.

In this case, since white (W) or black (K) is the same for the three primary color binary data R1, G1, and B1, if the ratio is increased, the three primary color binary data R1, G1 are used. , B1 has a high correlation characteristic. On the contrary, if a large weighting coefficient for multiplying the color difference of white (W) and black (K) is selected, the reproduction ratio of white (W) or black (K) becomes low due to error diffusion.

As described above, in the color laser printer, the color developability of the recorded image greatly varies depending on how the color toners are superposed. Therefore, by controlling the value of the correlation function, three or four color toners The color development can be stabilized by making the overlapping manner of a constant.

Further, according to the second means, the
The value of the correlation coefficient of the primary color binary data R1, G1, B1 is controlled, and the control here is necessary to reflect the user's preference or the compatibility of the recorded image pattern is considered. It is done because of the need. Specifically, regarding the obtained recorded image, a user who prefers a recorded image having a high correlation characteristic between the three primary color binary data R1, G1, and B1 and a user who prefers a recorded image having a low correlation characteristic. Also, with the recorded image, a pattern such as a high-definition line image is suitable for the recorded image having a high correlation characteristic, and a pattern such as a photograph is suitable for the recorded image having a low correlation characteristic. Furthermore, regarding the printing process of the color printer, cyan (C),
Magenta (M), Yellow (Y), Black (K) 4
When the colors are overlaid, the recorded image having a high correlation characteristic is suitable, and when the three colors of cyan (C), magenta (M), and yellow (Y) are overlaid, the correlation characteristic is low. The recorded image is suitable. In addition, depending on the type of coloring material, it is preferable that the coloring material having a low density is made to have a high density by the recorded image having a high correlation characteristic, and the coloring material having a low transparency is made a recording image having the low correlation characteristic. This is because it is preferable to obtain a bright OHP image.

In this way, the three primary color binary data R1, G1 and B are selected according to the respective conditions of the obtained recorded image.
By changing the correlation characteristic between 1 and 2 to be high, low, or in the middle thereof, it is possible to obtain a recorded image having a halftone of a suitable image quality.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

However, here, prior to the description of the embodiments of the present invention, in order to facilitate the understanding of the embodiments of the present invention, a known error diffusion method that has been executed during the conventional binarization processing is performed. I will describe.

FIG. 4 shows an example of the diffusion rule in this known error diffusion method.

In FIG. 4, (i-1, j), (i, j),
(I + 1, j) indicates the position of each of the pixels 41, 42, 43, and among them, for example, the reference pixel 42
, S (i, j) is the image data given to the pixel 42, T (i, j) is the error diffusion image data of the pixel 42 with the diffusion error added, and U (i, j) is 2 The binarized image data of the binarized pixel 42 is shown, and the other pixels 4
The same applies to 1 and 43.

Note that the example shown in FIG. 4 represents a diffusion rule that all the errors occurring in the pixel 41 on the left side of the reference pixel 42 are added to the reference pixel 42 for the sake of simplicity. Other pixels 42, 43
Similar diffusion rules are applied in between. In addition to this, in order to perform binarization, error diffusion pixel data T (i-1,
A judgment rule for binarizing j), T (i, j) and T (i + 1, j) is required.

In this case, if the diffusion rule and the judgment rule are respectively expressed by equations, the equations (1) and (2) below are obtained.

[0033]

[Equation 1]

[0034]

[Equation 2]

As described above, in the conventional binarizing process, the binarizing process of the 8-bit 3-primary color image data R8, G8, B8 is independently performed for each of the three primary colors, and therefore the pixel 42 is used. To the image data S (i, j) of the above, the three-primary-color image data R8, G8, B8 are sequentially substituted, and the binarized image data U (i, j) obtained by the binarization process Assuming binary data R1, G1 and B1, the above equations (1) and (2) are respectively represented by the following equations (3) to (5) and (6) to (8). It can be rewritten as an expression.

[0036]

[Equation 3]

[0037]

[Equation 4]

[0038]

[Equation 5]

[0039]

[Equation 6]

[0040]

[Equation 7]

[0041]

[Equation 8]

Next, in FIG. 5, the three primary color binary data R1, G1, and B1 obtained by the known error diffusion method are used for cyan (C), magenta (M), and yellow (Y) using a full-color laser printer. Recording of three colors C1, M1, and Y1 and four colors C in which black (K) is added to the above three colors
FIG. 3 is an explanatory diagram showing an example of recording 1, M1, Y1, and K1.

Then, (a) is the binary data R1 of three primary colors,
When the phases of G1 and B1 are aligned, (b) is the three primary colors 2
The case where the phase of the value data R1, G1, B1 is different from each other is shown, and (c) is the binary data R of three primary colors.
When the three colors are recorded when the phases of 1, G1 and B1 are aligned, (d) shows the three primary color binary data R1 and G1.
1 shows the case where the three colors are recorded when the phases of B1 are different from each other, and (e) shows the case where the phases of the three primary color binary data R1, G1, B1 are aligned. When recording the four colors by the 100% undercolor removal UCR, (f) is 100% undercolor removal UC when the phases of the three primary color binary data R1, G1, and B1 are different from each other.
The case where the recording of the four colors by R is performed is shown.

Here, the above-mentioned 100% undercolor removal UC
R means 100% of the portion expressing the black (K) by superimposing the three colors when recording the three colors.
By substituting one color of black (K), it means that recording of the four colors is performed.

By the way, in the example of the 8-bit 3-primary color image data R8, G8 and B8 shown in FIG. 5, in the 3-primary color lightness data (8 bits), R8 = 192/255,
It is a uniform image of light gray with G8 = 192/255 and B8 = 192/255. When this light gray image is binarized by a known error diffusion method, as shown in FIG.
The converted primary color binary data R1, G1, B1 are converted into binary data R1, G1, B1. Since the converted binary data R1, G1, B1 are binarized independently as described above, FIG. ), The three primary color binary data R1 and G
There are cases where the phases of 1 and B1 are aligned and where the phases of the three primary color binary data R1, G1 and B1 are different from each other as shown in FIG. 5B.

A full-color laser printer, like an offset printer, has toner images of cyan (C), magenta (M), yellow (Y) and, if necessary, black (K) on recording paper. Since the recording method in which each color is sequentially formed is adopted, as shown in FIG. 5C, three color toners of cyan (C), magenta (M), and yellow (Y) are formed on the recording paper. When the images overlap with each other, the transfer efficiency of the toner image of the color finally transferred to the recording paper may decrease, or the toner may peel due to excessive heat when fixing the transferred image to the recording paper. To do. Therefore, the density of the recorded image recorded on the recording paper becomes unstable, or the color developability deteriorates or peels due to insufficient heat when fixing the toner image of the color first transferred to the recording paper. There will be a problem of causing.

On the other hand, as shown in FIG.
On the recording paper, cyan (C), magenta (M),
If the three color toner images of yellow (Y) do not overlap each other, the above problem does not occur. Moreover, in the recording as shown in FIG. 5D, the principle of color mixing is additive color mixing, and this additive color mixing is reproduced after recording as compared with the recording by subtractive color mixing as shown in FIG. 5C. It has an advantage that the color can be easily predicted.

Although the description so far has been made on the case of recording three colors of cyan (C), magenta (M) and yellow (Y), black (K) is added to the three colors 4 In the case of recording a color, the aspect is different from that in the case of recording with the above three colors. That is, as shown in FIG. 5A, the three primary color binary data R1, G1,
When the phases of B1 are aligned, as shown in FIG. 5 (e), the toner image is completely replaced by one color of black (K) as shown in FIG. 5 (c). The above-mentioned problems due to the overlapping of the three color toner images do not occur.

On the other hand, as shown in FIG.
During the binarization process, the three primary color binary data R1, G1, B1
If the phases are different from each other, it is not possible to replace any part of the obtained recorded image with black (K), so the three colors of cyan (C), magenta (M), and yellow (Y) are superimposed. Therefore, it is necessary to express a gray color, and as shown in FIG. 5E, the color reproducibility becomes worse than in the case of expressing with one color of black (K).

As can be seen from the above description, the binary data R1, G1, B1 of the three primary colors can be obtained by using the color laser printer.
When the image recording is performed by the method, the correlation characteristic between the three primary color binary data R1, G1, and B1 has a great influence on the image quality of the obtained recorded image.

Here, if the correlation characteristic is defined by a statistical correlation coefficient r (xy), the correlation coefficient r (xy) is expressed by the following equation (9).

[0052]

[Equation 9]

In this case, when the correlation coefficient r (xy) is large, the frequency recorded by white (W) or black (K) becomes large as shown in FIG. When the correlation coefficient r (xy) is small, FIG.
As shown in (b), white (W) and black (K)
Will be recorded less frequently.

In the known binarization process, no consideration was given to the correlation coefficient r (xy), so that in one recorded image, due to the difference in the position of the image, a large number of images were recorded. Of the recorded image, the correlation coefficient r is different depending on the type of the image.
(Xy) becomes larger or smaller, and thus the recorded image obtained becomes unstable in color reproducibility and has uneven color.

Here, FIG. 1 is a block diagram showing an embodiment of a full-color image recording apparatus according to the present invention.

In FIG. 1, 1 is a binarization processing means, 2 is a temporary image memory device dedicated to red (R), 3 is a temporary image memory device dedicated to green (G), and 4 is a temporary image memory dedicated to blue (B). Image memory device, 5 is an optical disk device, 6 is a full color image scanner, 7 is a full color original document, 8 is a color laser printer, and 9 is a duplicated full color recording original document.

Then, 8-bit 3-primary color image data R8, G8, B obtained from the full-color image scanner 6
8 is supplied to the binarization processing means 1. Binary data R1, G1, B of three primary colors obtained by the binarization processing means 1.
1 is a temporary image memory device 2 dedicated to red (R),
The temporary image memory device 3 dedicated to green (G) and the temporary image memory device 4 dedicated to blue (B) are respectively supplied.

The full-color image recording apparatus according to this embodiment operates as described below.

First, the full-color image scanner 6
Scans the document of the full-color original document 7 and 8-bit image data R8, G8, B8 of three primary colors of red (R), green (G) and blue (B) color-separated for each pixel.
Are generated respectively. Next, the 8-bit three-primary-color image data R8, G8, B8 are all supplied to the binarization processing means 1. In the binarization processing means 1,
The three primary color image data R8, G8, and B8 are vectorized and binarized at one time, and as described below, error diffusion is performed using an error diffusion method peculiar to the present invention to obtain 1 bit. 3 primary color binary data R1 and G
1, converted to B1. Next, these three primary color binary data R1, G1, B1 are stored in the temporary image memory devices 2, 3, 4 dedicated to the respective colors red (R), green (G) and blue (B).
After being transferred to the optical disk device 5 and temporarily stored therein, the data is transferred to the optical disk device 5 and stored and stored therein together with other documents for an appropriate period.

On the other hand, in the optical disc device 5 in which a large number of documents are stored, the required document is read out from the optical disc device 5 according to the user's request, and the binary data R1, G1, and B1 of each color are separately classified. It is supplied to the corresponding temporary image memory devices 2, 3, 4. In the temporary image memory devices 2, 3, 4, after the user confirms the document, the binary data R1, G1, B of the three primary colors are displayed.
1 is supplied to a full-color laser printer 8, where an image recording using color toner by an electrophotographic method as known is performed, and a duplicated full-color recording original 9 is obtained.

Next, the error diffusion method peculiar to the present invention executed by the binarization processing means 1 will be described. However, the diffusion rule of the error diffusion method according to the present invention is the same as the diffusion rule of the known error diffusion method shown in FIG.

Particularly, in the error diffusion method according to the present invention, 8-bit 3-primary color image data R8, G8, B8 and 3-primary binary data R1, G1, B1 are collectively processed as vector quantities. It is a thing. In this case, the three primary color image data R8, G8, B8 and the three primary color binary data R1, G1, B1 are defined by the following equation (10).

[0063]

[Equation 10]

According to the above definition, the diffusion rule of the known error diffusion method shown in FIG. 4 is converted as shown in FIG.
Further, the formulas (3) to (5) are given below (1
It is expressed as in equation (1).

[0065]

[Equation 11]

However, as described above, since the diffusion rule of the error diffusion method according to the present invention is the same as the diffusion rule of the known error diffusion method, the equations (3) to (5) and the equation (11) are used.
The expressions are equivalent.

In this case, the feature of the present invention resides in the judgment rule for binarization in the expressions (6) to (8), and the judgment rules are the following expressions (12) and (13). )
It is expressed as an equation.

[0068]

[Equation 12]

[0069]

[Equation 13]

As shown in the equations (12) and (13), the feature of the present invention is that the position (i, j) shown in FIG.
From the error diffusion binary image data T (i, j) to which the diffused error has been added in the pixel at, 8 colors represented by the binary data, red (Ur), green (Ug), blue (Ub) , Cyan (Uc), magenta (Um), yellow (Uy),
Weighting factors ar, ag, ab, ac, am, and a are set for the distances to black (Uk) and white (Uw), respectively.
The point is that the above-mentioned determination rule by which y, ak, and aw are multiplied is used. Note that the known error diffusion method determination rule is that these weighting factors ar, ag, ab, ac, am, ay, a
This corresponds to the case where k and aw are selected as in the following expression (14).

[0071]

[Equation 14]

FIG. 7 is a three-dimensional structure diagram showing the relationship between the points of each color and the points of the binary image data when the contents of the equations (12) and (13) are followed.

In FIG. 7, the color of the pixel at the position (i, j) is 8 colors represented by the binary data, red (Ur),
Defined by the above formula (11) among the points indicated by green (Ug), blue (Ub), cyan (Uc), magenta (Um), yellow (Uy), black (Uk) and white (Uw) The color of the point closest to the generated error diffusion binary image data T (i, j) is selected as the color of the pixel at the position (i, j). On the other hand, according to the known error diffusion method determination rule, as shown in the equation (14), the probability that any one of the eight colors is selected is the same.

Further, in the present invention, each of the weighting factors ar, ag, ab, ac, am, shown in the above equation (13),
It is also possible to set ay, ak, and aw to values other than the values defined in the equation (13). It can be seen that if such a setting is made, a particular color among the eight colors shown in FIG. 7 can be easily selected or, on the contrary, difficult to be selected.

By the way, in the present embodiment, the respective weighting factors ar, ag, ab, ac, am, ay, ak, a used in the decision rule of the error diffusion method in the binarization process.
For w, select to satisfy the following expression (15), and
The valuation process is being executed.

[0076]

[Equation 15]

FIG. 8A is a three-dimensional structure diagram showing the relationship between the points of each color and the points of the binary image data when the expression (15) is satisfied.

As shown in FIG. 8A, in the diffusion error binary image data T (i, j), the distance to black (Uk) and the distance to white (Uw) are respectively multiplied by 0.4. Therefore, substantially, the black (Uk) and white (Uw) points are moved to the virtual black (Uk ′) point and the virtual white (Uw ′) point that are closer to the image data T (i, j) direction. This is equivalent to that of the binary image data T (i, j), and the color closest to the binary image data T (i, j) has a high probability of becoming the virtual black (Uk ′) or the virtual white (Uw ′). Thus, the error is diffused even if the probability that the black (Uk ′) or the white (Uw ′) is selected as the color of the binary image data T (i, j) is high. Therefore, the color reproducibility is the same as before.

Table 1 below shows i + k from the i-th pixel in the j-th scan line (where k = 0, 1, 2, ..., 15).
It shows an example of binarized output up to the th pixel.

However, similarly to the example shown in FIG. 5, the i-th pixel to the i + k-th pixel satisfy the following expression (16), and the diffusion error (initial value) shown in the above expression (11) is satisfied. The condition) is a binarization process using the known error diffusion method determination rule shown in the equation (14) for the first and second cases shown in the following equations (17) and (18). The output is obtained when the binarization process is performed and when the binarization process is performed using the determination rule of the error diffusion method of the present invention represented by the equation (15).

[0081]

[Equation 16]

[0082]

[Equation 17]

[0083]

[Equation 18]

[0084]

[Table 1]

According to Table 1, in the first case, when the known binarization process is performed, as shown in FIG. 5B, the three primary color binary data R1, G1, B1 are obtained. Position of the three primary color binary data R1, G1,
The correlation coefficient between B1 (see the above equation (9)) becomes small.
On the other hand, when the binarization processing of the present embodiment is performed, in each pixel after U (i + 5, J), as shown in FIG. , G1, B1 are aligned, and the three primary color binary data R1, G1,
The correlation coefficient between B1 becomes large.

On the other hand, in the second case, the known 2
In both the case where the binarization process is performed and the case where the binarization process of this embodiment is performed, the three primary color binary data R1 and G
1 and B1 are prepared, and binary data of three primary colors R1, G1,
The correlation coefficient between B1 is large.

Although the first and second cases mentioned above are both typical examples, the position (i, j)
Even if the diffusion error (initial condition) added to the pixel is a case other than the first and second cases, when the known binarization processing is performed, the error is 3 depending on the case.
While the correlation coefficient between the primary color binary data R1, G1, and B1 increases or decreases, when the binarization processing of this embodiment is performed, After the binarization process, the probability that two colors of black (Uk) and white (Uw) will appear is high, and therefore the correlation coefficient between the three primary color binary data R1, G1, and B1 is large.

In the binarization process of this embodiment, the two weighting factors ak and aw are selected to be 0.4 in the equation (15), but these weighting factors ak and aw are selected. The smaller the numerical value of 1 is, the higher the probability that two colors of black (Uk) and white (Uw) will appear. However, if the above value is made too small, the error due to the error diffusion method will be accumulated.
The numerical value cannot be extremely reduced.

As described above, according to the present embodiment, the correlation coefficient between the binary data R1, G1, and B1 of the three primary colors after the binarization process becomes large, so that as shown in FIG. If 100% undercolor removal is performed in the laser printer 8,
The ratio of black (Uk) substitution is high, and when recording is performed using the color laser printer 8, it is possible to obtain a stable recorded image of high image quality.

Next, FIG. 8B is a three-dimensional structure diagram showing the relationship between the points of each color and the points of the binary image data in the case of the second embodiment of the judgment rule of the diffusion processing method according to the present invention. is there.

The second embodiment of the decision rule of the diffusion processing method is that each weighting coefficient ar, ag, ab, ac, am, ay,
The ak and aw are selected as in the following equation (19) and the binarization processing is executed.

[0092]

[Formula 19]

As shown in FIG. 8B, in the present embodiment, the binary image data T for the pixel at the position (i, j).
Since the distance from the (i, j) point to the black (Uk) point and the distance to the white (Uw) point are both multiplied by 2.5, each of the black (Uk) and white (Uw) points is actually A virtual black (Uk ') point and a virtual white (Uw') that are distant from the binary image data T (i, j) point.
It is equivalent to moving to a point. Therefore, the color of the point closest to the binary image data T (i, j) point is black (U
k) or white (Uw) is less likely. Also in this case, since the error is diffused, the color reproducibility does not change.

Next, Table 2 shows a case in which the known binarization process is performed for the first and second cases shown in Table 1 under the same conditions as those in Table 1, and It is shown by comparing each binarized output when the binarization processing of the embodiment is performed.

[0095]

[Table 2]

According to Table 2 above, in the case of the first case, both of the known binarization process and the binarization process of the present embodiment, the three primary colors are performed. The binary data R1, G1, B1 are scattered, and the correlation coefficient between the three primary color binary data R1, G1, B1 data is small.

In the case of the second case, the known 2
When the binarization process is performed, as shown in FIG.
The three primary color binary data R1, G1, and B1 come to be aligned,
The correlation coefficient between the three primary color binary data R1, G1, and B1 becomes large. However, when the binarization processing of the present embodiment is performed, as shown in FIG.
1, G1, B1 are separated, and the three primary color binary data R
The correlation coefficient between 1, G1 and B1 becomes small.

As described above, according to this embodiment, the three primary color binary data R1, G1, and B1 are always separated regardless of the diffusion error (initial condition) added to the pixel at the position (i, j). .

Also in the case of the present embodiment, both the first case and the second case mentioned above are typical examples, but the diffusion error added to the pixel at the position (i, j) is Even in cases other than the first case and the second case (initial condition), when the known binarization processing is performed, the correlation coefficient between the three primary color binary data R1, G1, and B1 is When the binarization processing of the present embodiment is performed, while it becomes large or small,
Obviously, the probability that two colors of black (Uk) and white (Uw) appear after the binarization processing becomes low, and the three primary colors 2
The correlation coefficient between the value data R1, G1, B1 becomes smaller.

Further, in this embodiment, 2.5 is selected as the numerical value of the two weighting factors ak and aw, but the larger the numerical value is, the more the black (Uk) and white (Uw) The probability of two colors appearing is low,
If this value is made too large, the error due to the error diffusion method will be accumulated, and therefore the value cannot be made extremely large.

As described above, according to this embodiment, the correlation coefficient between the binary data R1, G1, and B1 of the three primary colors after the binarization processing becomes small, so that as shown in FIG. Cyan (C), magenta (M) using the printer 8,
When three-color recording of yellow (Y) is performed, the proportion of any two of the three colors and all three colors overlapping is low, and a stable high-quality recorded image can be obtained.

FIG. 2 is a block diagram showing an example of the internal configuration of the binarization processing means 1 shown in FIG.

In FIG. 2, 10 is a microcomputer, 11 is an input line, 12 is a pixel synchronizing signal (PEL) line, 13 is a line synchronizing signal (LINE) line,
14 is an output line.

Then, the microcomputer 10 has the 8-bit red (R), green (G) and blue (B) image data R8 and G respectively.
8, B8 are supplied via the input line 11, the pixel synchronization signal (PEL) line 12 receives the pixel synchronization signal (PEL), and the line synchronization signal (LINE) line 13 receives the line synchronization signal (L).
INE) respectively and output lines 14 to 3
The primary color binary data R1, G1, and B1 are transmitted.

In the above structure, the microcomputer 10 is a PE
The image data R8, G8 from the input line 11 are synchronized with the pixel synchronization signal (PEL) and the line synchronization signal (LINE) supplied via the L line 12 and the LINE line 13.
B8 is input, these image data R8, G8, B8 are vectorized to perform arithmetic binarization processing, and the three primary color binary data R1, G1, B1 are output to the output line 14.

Next, FIG. 3 is a block diagram showing another embodiment of the full-color image recording apparatus according to the present invention.

In FIG. 3, 15 is a binarization processing means, 1
Reference numeral 6 is a correlation coefficient control means, 17 is a brightness detection means, 18 is an area determination means, and 19 is a user instruction means.

Then, the full-color image scanner 6
The output (see FIG. 1) is directly connected to the input of the binarization processing means 15, and is also connected to the inputs of the brightness detection means 17 and the area determination means 18, respectively. The outputs of the brightness detection means 17 and the area determination means 18 are connected to the correlation coefficient control means 16, and the outputs of the correlation coefficient control means 16 are connected to the binarization processing means 15. The output of the user instruction means 19 is also connected to the correlation coefficient control means 16, and the output side of the binarization processing means 15 is a temporary image memory device 2 dedicated to red (R) and a dedicated temporary image memory device 2 dedicated to green (G). A color laser printer 8 is connected via a temporary image memory device 3 and a temporary image memory device 4 dedicated to blue (B) (see FIG. 1).

The full-color image recording apparatus according to this embodiment operates as described below.

As described above, the color laser printer 8
Adopts a method in which toner images of cyan (C), magenta (M), yellow (Y), and black (K) are sequentially transferred one by one onto recording paper, as is done with an offset printing apparatus. Therefore, it is possible to form a color recording image with three colors of cyan (C), magenta (M), and yellow (Y) without using black (K) (this is called a three primary color mode). . By the way, in the recording image in the three primary color mode, in addition to the above three colors, black (K) is used, and a color recording image in which 100% undercolor is removed is formed (this is referred to as an undercolor removal mode).
When compared with the recorded image obtained in, the image quality of the recorded image differs slightly due to the difference in the colorimetric characteristics of the toner,
Users may have different tastes.

Therefore, in this embodiment, the user instruction means 19 is connected to the correlation coefficient control means 16. The user instructing means 19 uses the binarization processing means 15 when the recorded image is obtained by color image recording in the three primary color mode.
In the binarization processing in, the weighting coefficients ar, ag, ab, ac, which are set in the correlation coefficient control unit 16,
Am, ay, ak, and aw are determined, for example, as in the equation (15), and are operated so as to increase the correlation coefficient between the three primary color binary data R1, G1, and B1. On the other hand, when a recorded image is obtained by color image recording in the under color removal mode, conversely, in the binarization processing by the binarization processing means 15,
Each weighting coefficient a set in the correlation coefficient control means 16
r, ag, ab, ac, am, ay, ak, and aw are set, for example, as in the equation (19), and act to reduce the correlation coefficient between the three primary color binary data R1, G1, and B1. Let

According to this embodiment, the user inputs the weighting factors ar, ag, ab, ac, am, ay, ak, aw in the correlation coefficient control means 16 by the user instruction means 19.
By making the change setting, it is possible to always obtain a stable high-quality recorded image regardless of whether the color image recording in the three primary color mode or the color image recording in the under color removal mode is selected. However, when the document is stored and stored in the optical disk device 5 shown in FIG. 1, it is necessary to simultaneously store in which of the three primary color modes or the undercolor removal mode the binarization processing is performed. .

In this case, even when the color image recording in the under color removal mode is performed, the toner images of the respective colors overlap relatively in a low density area of the recorded image, so that the three primary colors are forced. Binary data R1, G1, B
When it is attempted to superimpose the toner images of the respective colors by increasing the correlation coefficient between 1 and 1, the positional deviation between the toner images of the respective colors becomes conspicuous, and the image quality of the recorded image deteriorates. Therefore, in the high concentration region, 3
Even if it is necessary to increase the correlation coefficient between the primary color binary data R1, G1, and B1 to remove the undercolor, the correlation coefficient is decreased in the low density region to reduce the influence of the positional deviation. Will need to be reduced.

In this embodiment, the brightness detecting means 17 is provided, and the brightness detecting means 17 determines the brightness Y of the 8-bit 3-primary color image data R8, G8, B8 as the following (20). It is calculated by the formula.

[0115]

[Equation 20]

In the equation (20), when the luminance Y of the 8-bit 3-primary color image data R8, G8, B8 is high luminance (for example, Y> 0.7), it is low when the recorded image is obtained. Since the density is reached, the brightness detecting means 17 reduces the correlation coefficient between the three primary color binary data R1, G1, and B1,
The correlation coefficient control means 16 is instructed to that effect. Conversely, when the luminance Y is low (for example, Y <0.3)
Since the density becomes high when a recorded image is obtained, the luminance detecting means 17 instructs the correlation coefficient controlling means 16 to increase the correlation coefficient. As described above, according to the present embodiment, it is possible to prevent the image quality from being deteriorated such as the positional deviation that occurs in the low density area when the under color removal mode is executed.

Further, in this embodiment, the area judging means 18 used in the known electronic filing system shown in FIG. 10 is provided, and the judgment result obtained by the area judging means 18 is compared. Relation number control means 1
I am trying to input in 6. For example, the binarization processing is performed while controlling the correlation coefficient of the three primary color binary data R1, G1, and B1 in the area determined to have many areas of uniform density in the recorded image. However, the binarization process is executed without controlling the correlation coefficient for the region where it is determined that there are many fine parts.
By performing such binarization processing, it becomes possible to stabilize the recorded image in the case of an image having many areas of uniform density.

[0118]

As described above, according to the present invention,
When performing the binarization process of the three primary color image data R8, G8, B8, the correlation coefficient of the three primary color binary data R1, G1, B1 obtained by the binarization process is controlled. When three-color recording of cyan (C), magenta (M), and yellow (Y) is performed using the laser printer 8 and also when four-color recording including black (K) in the three colors is performed. Also in this case, it is possible to perform image recording in which color reproduction is faithfully performed, and it is possible to obtain image recording with stable image quality without color unevenness.

According to the present invention, the correlation coefficient is
Since it can be changed according to the user's preference, the brightness of the recorded image, and the result of the area determination of the recorded image, it is possible to obtain a suitable image recording in various points. There is an effect.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of a full-color image recording apparatus according to the present invention.

2 is a block configuration diagram showing an example of an internal configuration of a binarization processing unit used in the full-color image recording apparatus of FIG.

FIG. 3 is a block diagram showing another embodiment of the full-color image recording apparatus according to the present invention.

FIG. 4 is an explanatory diagram showing an example of a diffusion rule in a known error diffusion method.

FIG. 5 is an explanatory diagram showing a case where three-color recording and four-color recording are performed by a full-color laser printer on binary data of three primary colors obtained by a known error diffusion method.

FIG. 6 is an explanatory diagram showing an example of a diffusion rule in the error diffusion method of the present invention.

FIG. 7 is a three-dimensional structure diagram showing the relationship between binary image data points and eight color points.

FIG. 8 is a three-dimensional structure diagram showing the relationship between binary image data points and eight color points when the correlation coefficient is changed.

FIG. 9 is a block configuration diagram showing an example of a schematic configuration in a known electronic filing system (full color system).

FIG. 10 is a block configuration diagram showing an example of a schematic configuration in a known electronic filing system (monochrome system).

[Explanation of symbols]

 1, 15 Binarization Processing Means 2 Red (R) Dedicated Temporary Image Memory Device 3 Green (G) Dedicated Temporary Image Memory Device 4 Blue (B) Dedicated Temporary Image Memory Device 5 Optical Disc Device 6 Full Color Image Scanner 7 Full Color Document 8 Full-color laser printer 9 Duplicate full-color recording document 10 Microcomputer 11 Input line 12 Pixel synchronization signal (PEL) line 13 Line synchronization signal (LINE) line 14 Output line 16 Correlation coefficient control means 17 Luminance detection means 18 area determination means 19 user instruction means

Claims (7)

[Claims] 1. Three-primary color data of a full-color image is converted into three-primary-color binary data by binarization processing,
In a full-color image recording apparatus that temporarily stores the value data in the memory and then reads the value data from the memory to perform full-color recording, when the binarization processing is performed, 3 of the full-color image is recorded.
After vectorizing the primary color data, error diffusion is collectively performed, and when the color difference between the pixel data to which a diffusion error is added due to this error diffusion and the respective three primary color binary data is calculated, the color difference is weighted. A full-color image recording apparatus, wherein a value of a correlation coefficient of the binary data of the three primary colors is controlled by multiplying the coefficient. 2. The binarization process uses a color laser printer to print cyan (C), magenta (M), and yellow (Y).
2. The full-color image recording apparatus according to claim 1, wherein the value of the correlation coefficient is controlled so that the correlation coefficient of the binary data of the three primary colors becomes small when recording is performed with the three primary colors. . 3. The binarization process uses a color laser printer to print cyan (C), magenta (M), and yellow (Y).
In addition to the three primary colors, black (K) is added to perform recording by removing the undercolor, the value of the correlation coefficient is controlled so that the correlation coefficient of the binary data of the three primary colors becomes large. The full-color image recording apparatus according to claim 1, wherein 4. The full-color image recording apparatus according to claim 1, wherein in the binarization process, a value of a correlation coefficient of the binary data of the three primary colors is manually controllable. 5. The binarizing process, when recording is performed by removing undercolor by adding black (K) in addition to the three primary colors of cyan (C), magenta (M), and yellow (Y), 4. The full-color image recording apparatus according to claim 1, wherein the value of the correlation coefficient is controlled so that the correlation coefficient of the binary data of the three primary colors changes according to the brightness of the image. 6. The value of the correlation coefficient is controlled such that the correlation coefficient of the binary data of the three primary colors becomes small when the brightness of the image is high and becomes large when the brightness of the image is low. The full-color image recording apparatus according to claim 5, which is performed. 7. The binarizing process, when recording is performed by removing undercolor by adding black (K) in addition to the three primary colors of cyan (C), magenta (M), and yellow (Y), 7. The full color according to claim 1, wherein the value of the correlation coefficient is controlled so that the correlation coefficient of the binary data of the three primary colors changes according to the result of the area determination. Image recording device.