JPH07210672A - Method and device for binarization - Google Patents

Abstract

PURPOSE:To keep the gradation more than the conventional dither method and to speed up the processing speed more than the error diffusion method in binarizing the multilevel data picture. CONSTITUTION:A pixel division part 401 divides the picture element plane into cells. A cell selecting part 402 decides the noticed cell. Then, a total calculation part 403 obtains the total value SIGMA of the density value of the whole composed pixels of the noticed cell. Then, a subtraction part 404 divides the total value SIGMA by the gradation number such as 256. A pixel selection part 405 takes the quotient obtained by the part 404 in the order of high density value among all pixels of the noticed cell. A binarization part 406 performs binarization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binarization method, for example, a binarization method when an RGB multi-valued image is output as a binary CMYK full color image.

[0002]

2. Description of the Related Art Conventionally, as a binarizing method for tone reproduction of a color image when outputting an RGB multi-valued image as a binary CMYK full color image in a recording apparatus such as thermal transfer recording, ink jet recording, electrophotographic recording, etc. , Many methods have been proposed. Among them, the systematic dither method and the error diffusion method are usually most frequently used.

[0003]

However, the above-mentioned conventional binarization method has the following drawbacks. For example, the systematic dither method has a simple device configuration and does not require complicated calculations, and thus has a high processing speed, but it is difficult to maintain gradation, and the error diffusion method maintains gradation, but it is complicated. Since it requires various device configurations and calculations, the processing speed is slow.

[0004]

The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, a binarization device for converting multivalued data of gradation expression into binary data, comprising a pixel dividing means for dividing a pixel plane of the multivalued data image into cells of a predetermined matrix, and the pixel dividing means. Cell selecting means for selecting a cell to be processed among cells obtained by the division by, a total sum calculating means for obtaining a total sum of density values of all pixels forming the cell selected by the cell selecting means, and the total sum calculation Dividing means for dividing the total sum calculated by the means by the number of gradations of the multi-valued data, and density of the same number of pixels as the quotient obtained by the dividing means from all the pixels forming the cell selected by the cell selecting means It has a pixel selection means for selecting in descending order of the value, and the pixel selected by the pixel selection means is one of the binarization.

For example, the pixel dividing means divides the pixel plane of the multi-valued data image into cells of an 8 × 8 matrix, and 8 × n (0 <n
<8, n is an integer) and there is a pixel group that cannot be divided m × 8 (0 <m <8, m is an integer)
It is characterized in that it is divided into an m × n matrix when there is a pixel group that cannot be divided.

[0006]

With the above construction, in the binarization processing of a multi-valued data image, it is possible to maintain the gradation property more than the conventional dither method, and to increase the processing speed more than the error diffusion method. Has the effect of.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view showing the internal structure of a laser beam printer (LBP) 100 according to the present embodiment. This LBP 100 is used for registering character patterns from a data source (host computer, etc.) (not shown) and for writing fixed form (form data). It is configured to allow registration.

In FIG. 1, reference numeral 100 denotes an LBP main body, which inputs and stores character information (character code) supplied from an externally connected host computer or the like, form information, macro commands, and the like. A corresponding character pattern, form pattern, or the like is created according to the information, and an image is formed on a recording paper, which is a recording medium. Three
Reference numeral 00 is an operation panel on which various switches for operation and LED displays are arranged, and 101 is a printer control unit for controlling the entire LBP 100 and analyzing character information and the like supplied from the host computer. The printer control unit 101 mainly converts character information into a video signal of a corresponding character pattern and outputs it to the laser driver 102.

The laser driver 102 is a semiconductor laser 10.
3 is a circuit for driving the semiconductor laser 3, and switches the semiconductor laser on and off in accordance with the input video signal. The laser light 104 is swung in the left-right direction by the rotary polygon mirror 105 to scan the electrostatic drum 106. As a result, an electrostatic latent image having a character pattern is formed on the electrostatic drum 106. The latent image is formed on the developing unit 107 around the electrostatic drum 106.
And then transferred to a recording paper. A cut sheet is used for this recording paper, and the LBP10 cassette recording paper is used.
The paper feed roller 10
It is taken into the apparatus by the 9 and the conveyance rollers 110 and 111 and is supplied to the electrostatic drum 106.

In this embodiment, an RGB multi-valued data image on a color monitor in an information processing system such as a personal computer is converted into CMYK multi-valued data by a known method such as logarithmic conversion in the printer control unit 101 of the LBP 100 described above. The cyan pixel plane after conversion into an image will be described as an example. Note that multi-valued data of each color of RGB is represented by 256 gradations.

FIG. 2 shows a cyan pixel plane described as the present embodiment. In the cyan pixel plane of FIG. 2, each constituent pixel is divided into an 8 × 8 matrix, and the number of surplus pixels n (0 <n <8, n in the main scanning direction on the cyan pixel plane.
Is an integer), and the number of surplus pixels m (0 <m
<8, m is an integer) occurs. Therefore, in the cyan pixel plane of FIG. 2, 8 × 8 cells 1 and 8 × n, which are hatched, are shown.
Cells of four patterns of cells 2, cells 3 of m × 8, and cells 4 of m × n are generated.

In this embodiment, m = n = 4,
The description will be given below. FIG. 3 shows an example of multi-valued data of each constituent pixel in the cells of the four-pattern matrix shown in FIG. 2 described above. 3A shows multi-valued data forming an 8 × 8 cell, that is, an example of the density value of each pixel, and FIG. 3B shows multi-valued data forming an 8 × 4 cell, that is, 3C shows an example of the density value of each pixel, FIG. 3C shows an example of the density value of each pixel, that is, the multi-valued data forming a 4 × 8 cell,
FIG. 3D shows an example of multivalued data forming a 4 × 4 cell, that is, the density value of each pixel. Therefore, the cell 1 shown in FIG. 2 is shown in FIG. 3A, the cell 2 is shown in FIG.
Corresponds to (c) of FIG. 3 and cell 4 corresponds to (d) of FIG.

A method of converting multivalued data into binary data on the cyan pixel plane divided into the above matrix will be described with reference to the block diagram of FIG. FIG. 4 is a block configuration diagram of a binarization unit that performs binarization in the printer control unit 101 of the LBP 100 of this embodiment. In FIG. 4, reference numeral 401 denotes a pixel division unit that divides input pixel plane data into, for example, 8 × 8 cells and stores the cells in the memory 407. A cell selection unit 402 selects a cell of interest from among the cells divided by the pixel division unit 401 and stored in the memory 407. Reference numeral 403 denotes a total sum calculation unit that calculates the total sum of the density values of the pixels forming the cell of interest selected by the cell selection unit 402. 404
Is a division unit, and the sum of the density values obtained in 403 is divided by the number of gradations such as 256 to obtain the quotient. Reference numeral 405 denotes a pixel selection unit, which selects a pixel to be binarized in the cell of interest.
The number of quotients obtained by the division unit 404 is selected. A binarization unit 406 converts each pixel in the cell of interest selected by the pixel selection unit 405 as one of binarization.

As described above, with the configuration shown in FIG. 4, the pixel plane stored in the memory 407 is binarized for each cell divided by the pixel division unit 401. The binarization process in this embodiment as described above will be described in more detail with reference to the flowchart of FIG. Figure 5
3 is a flowchart showing the flow of binarization processing in this embodiment.

In step S301 of FIG. 5, the pixel dividing unit 401 of FIG. 4 sets the cyan pixel plane shown in FIG.
8 is divided into 8 matrices, cells of 8 × 8 matrix 201 shown in FIG. 2 are created, and stored in the memory 407. Then, in step S302, if the division process is completed for all pixels, the process proceeds to step S308, but if an unprocessed pixel group that cannot be divided into 8 × 8 remains, the process proceeds to step S303.

In step S303, the pixel division unit 401 divides the unprocessed pixel group by 8 × n, that is, 8 in this embodiment.
The division processing into the × 4 matrix is performed to create the cells of the 8 × 4 matrix indicated by 202 in FIG.
To store. Then, in step S304, it is determined whether or not all the division processes have been completed. If it is determined in step S304 that the division is completed, the process proceeds to step S308, but if a pixel group that cannot be divided into 8 × 4 remains, the process proceeds to step S305.

In step S305, for the unprocessed pixel group, the pixel division unit 401 has m × 8, that is, 4 pixels in this embodiment.
The division processing into the × 8 matrix is performed to create the cells of the 4 × 8 matrix indicated by 203 in FIG.
Store to. In step S306, it is determined whether the division process has been completed for all pixels. Step S306
If it is determined that the division processing has been completed for all the pixels in step S308, the process proceeds to step S308. However, if an unprocessed pixel group remains, the process proceeds to step S307, and the pixel division unit 401 determines the unprocessed pixel group. Then, one m × n, that is, a cell of a 4 × 4 matrix shown by 204 in FIG. 2 in this embodiment is created and stored in the memory 407. Then, the process proceeds to step S308.

By the processing in steps S301 to S307 as described above, the memory 4 as shown in FIG.
In 07, the cyan pixel plane is divided and stored in each cell. The processing after step S308 will be described with reference to FIG. In this embodiment, step S3
Each cell divided up to 07 is binarized. First, in step S308, the cell selection unit 402 shown in FIG.
Of the cells in the memory 407, the cell of interest is determined. In this embodiment, first, the cell 1 shown in FIG. 2 is selected as the pixel of interest. The processing order of cells in this case is not particularly limited, and any processing order is possible,
It can be arbitrarily determined according to the reading / writing method of the cell of the processing device.

Next, in step S309, the total sum calculation unit 403 obtains all multivalued data of the target cell, that is, the total sum Σ of the density values of all the constituent pixels. In the case of the present embodiment, the sum Σ of the density values of the constituent pixels of the cell 1 shown in FIG. 2, that is, the cell shown in FIG.
Then, a process progresses to step S310 and the division part 404.
Divides the total sum Σ obtained in the previous step S309 by the number of gradations. In the case of this embodiment, since there are 256 gradations, the sum Σ of density values is divided by 256.

In step S311, the pixel selection unit 405 selects, as processing pixels, the quotient obtained by the division in step S310, in order from the largest density value of all the constituent pixels of the target cell. Then, the binarization unit 406 performs binarization. As a method of selecting pixels in descending order of density value, various known methods can be used.

The above steps S308 to S3
When the operation of 11 is described by a mathematical expression, the sum Σ of the density values of all the constituent pixels of the cell 1 shown in FIG. 3A is 8252, and therefore, when the sum Σ is divided by the number of gradations 256, it is as follows. Become. 8252/256 = 32.2578 ... That is, among the constituent pixels of the cell 1 shown in FIG. 3A, 32 pixels having the largest density value are selected as the processing pixels.

In FIG. 5, finally, in step S312, it is determined whether the processing has been completed for all cells. If it is determined in step S312 that the processing has been completed for all cells, the binarization processing in this embodiment ends, but if there are unprocessed cells, the process returns to step S308, and then the binary processing is performed. The cell to be processed is determined.

When the binarization process is completed for all 8 × 8 cells such as cell 1 in FIG. 2 as described above, then, for example, 8 × n cells such as cell 1 in FIG. Binarization processing is performed for all cells. Then, the binarization process is performed on all m × 8 cells such as the cell 3 in FIG. 2, and finally the m × n binarization process on the cell 4 in FIG. 2 is performed. Complete the binarization.

An example in which the cells of FIGS. 3A to 3D are processed by the binarization method of this embodiment is shown in FIGS.
Each is shown in (d). For example, (a) of FIG.
In the cell 1 shown in (a) of FIG. 3, the 32 pixels selected based on the above-described process are shown, and the pixels circled in the figure are the selected pixels. FIG. 6B-
Also in (d), the pixels marked with circles are the pixels selected by the binarization method of this embodiment.

As described above, the binarization process is performed on all the cells divided in the cyan pixel plane of this embodiment. Further, with respect to the magenta and yellow pixel planes, binarization can be performed in the same manner as the cyan pixel plane. As described above, according to this embodiment,
In the binarization processing of a multi-valued data image, it is possible to maintain the gradation property as compared with the conventional dither method, and it is possible to increase the processing speed as compared with the error diffusion method.

In the present embodiment, the pixel plane is 8 ×
Although the processing is performed by dividing the matrix into eight matrices, the present invention is not limited to this example, and an appropriate dividing method can be adopted according to the image processing apparatus. Further, although the example of the binarization processing in the multi-valued data of 256 gradations has been described in the present embodiment, the present embodiment can be applied to other gradation numbers.

Further, although the present invention has been described with respect to the laser beam printer, the present invention is not limited to the example of the printer as a matter of course, and binarizes multi-valued image data such as a copying machine or a facsimile machine. It is applicable to all devices that need to be installed. The present invention may be applied to a system including a plurality of devices or an apparatus including one device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0028]

As described above, according to the present invention, in the binarization processing of a multi-valued data image, gradation can be maintained more than the conventional dither method, and the processing speed is higher than that of the error diffusion method. It is possible to raise.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a laser beam printer in an embodiment according to the present invention.

FIG. 2 is a diagram showing a state in which a cyan pixel plane before binarization in this embodiment is divided into cells.

FIG. 3 is a diagram showing an example of density values in each cell of a cyan pixel plane before binarization in the present embodiment.

FIG. 4 is a block diagram showing a configuration of a binarization unit in this embodiment.

FIG. 5 is a flowchart showing a binarization method in this embodiment.

FIG. 6 is a diagram showing an example in which each cell in this embodiment is binarized.

[Explanation of symbols]

 401 pixel division unit 402 cell selection unit 403 total sum calculation unit 404 division unit 405 pixel selection unit 406 binarization unit 407 memory

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/40 103 A

Claims (10)

[Claims] 1. A binarization method in a binarization device for converting multivalued data of gradation expression into binary data, wherein a pixel for dividing a pixel plane of the multivalued data image into cells of a predetermined matrix. A division process, a cell selection process for selecting a cell to be processed among the cells obtained by the division by the pixel division process, and a sum total of density values of all pixels forming the cell selected by the cell selection process Total sum calculation step, a division step of dividing the total sum calculated by the total sum calculation step by the number of gradations of the multi-valued data, and obtained by the division step from all the pixels constituting the cells selected by the cell selection step. A pixel selection step of selecting the same number of pixels as the quotient in descending order of density value, and the pixel selected by the pixel selection step is one of the binarization methods. 2. The binarization method according to claim 1, wherein the pixel division step divides the pixel plane of the multi-valued data image into cells of an 8 × 8 matrix. 3. The pixel dividing step is to divide into a matrix of 8 × n (0 <n <8, n is an integer) when there is a pixel group that cannot be divided into cells in the pixel plane of the multi-valued data image. The binarization method according to claim 2, which is characterized in that. 4. The pixel dividing step divides into a matrix of m × 8 (0 <m <8, m is an integer) when there is a pixel group that cannot be divided into cells in the pixel plane of the multi-valued data image. The binarization method according to claim 3, which is characterized in that 5. The binarization according to claim 4, wherein the pixel division process is divided into an m × n matrix when there is a pixel group that cannot be divided into cells in a pixel plane of the multi-valued data image. Method. 6. A binarization device for converting multivalued data of gradation expression into binary data, comprising a pixel dividing means for dividing a pixel plane of the multivalued data image into cells of a predetermined matrix, Cell selecting means for selecting a cell to be processed among the cells obtained by the division by the pixel dividing means, and a sum total calculating means for obtaining the sum of the density values of all the pixels forming the cell selected by the cell selecting means, A division unit that divides the total sum calculated by the total sum calculation unit by the number of gradations of the multi-valued data, and a quotient equal to the quotient obtained by the division unit from all the pixels that constitute the cell selected by the cell selection unit. A binarization device comprising: a pixel selection unit that selects pixels in descending order of density value, and the pixel selected by the pixel selection unit is one of binarization. 7. The binarization device according to claim 6, wherein the pixel dividing unit divides the pixel plane of the multi-valued data image into cells of an 8 × 8 matrix. 8. The pixel dividing means divides into a matrix of 8 × n (0 <n <8, n is an integer) when there is a pixel group that cannot be divided into cells in a pixel plane of the multi-valued data image. The binarization device according to claim 7, which is characterized in that. 9. The pixel dividing means divides into a matrix of m × 8 (0 <m <8, m is an integer) when there is a pixel group that cannot be divided into cells in the pixel plane of the multi-valued data image. 9. The binarization device according to claim 8, which is characterized in that. 10. The binarization according to claim 9, wherein the pixel dividing means divides into a matrix of m × n when there is a pixel group which cannot be divided into cells in a pixel plane of the multi-valued data image. apparatus.