KR100280179B1 - How to handle color halftones to prevent ink overlap - Google Patents

Abstract

The present invention relates to a color halftone processing method for preventing ink overlap, which prevents the overlapping phenomenon that occurs when printing an image using three-color (C, M, Y) inks in a three-color printing system. Binary synthesized image (C + M) consisting of the sum of (C) and magenta (M) to determine the background of the pixel of interest, and when the pixel of interest has a background character, the cyan (M) and magenta (M) ) And binarize by setting each component to 0. If the pixel of interest does not have a background characteristic, it is determined whether the sum of the grayscale values of cyan and magenta (M) for the pixel of interest is equal to or less than a predetermined value. When the predetermined value is less than a predetermined value, the corrected pixel value ti_c of cyan (C) is compared with the size of the modified pixel value ti_m of magenta (M), and the modified pixel value ti_c of cyan (C) is compared. If it is larger than the corrected pixel of interest (ti_m) of this magenta (M) The green (C) component is set to 1 and the magenta (M) component is set to 0. If the modified pixel value (ti_c) of cyan is smaller than the modified pixel value (ti_m) of magenta (M), it is cyan. (C) The component is set to 0 and the magenta (M) component is set to 1 and binarized. When the sum of the respective grayscale values of cyan (C) and magenta (M) exceeds the predetermined value, independently of cyan (C) and Perform binarization on magenta (M).

Description

How to handle color halftones to prevent ink overlap

The present invention relates to a color halftone processing method, and more particularly, to overlap ink that prevents the overlapping phenomenon that occurs when printing an image using three-color (C, M, Y) inks in a three-color printing system. It is related with the collar halftone processing method which prevents.

Referring to Fig. 1, a general multifunction printer having a color printing unit, which is one of three color printing systems, will be described. A central processing unit (CPU) 1 which controls and processes the system according to a predetermined program, A reading unit 2 for converting pictures or characters into regular intervals and converting them into electrical energy having contrast, and transmitting digital image data to the central processing unit 1, program data, protocol data, character data, and recorded data. The memory unit 3 stores voice data and accesses or stores data according to the control of the central processing unit 1, and data output from the central processing unit 1 under the control of the central processing unit 1 is analog. Modem 4 which modulates and outputs the received input signal while demodulating and outputting the input signal, and efficient processing of data input / output to / from modem 4 The code / decoding unit 5 which encodes or decodes the data under the control of the central processing unit 1 and the call loop of the telephone line under the control of the central processing unit 1 is formed. A network controller 6 for interfacing a signal and a signal of a telephone line, and a plurality of keys and a display device are provided for inputting various control commands and under the control of the central processing unit 1 to control the state of the system. An operating panel 7 for displaying a variety of information, a conventional computer 8 having a main memory device or an auxiliary memory device, and contents stored in the computer 8 by expressing the original information by color printing through an arbitrary transmission line. Printer 9 capable of color printing, data received or transmitted via modem 4, data stored in memory 3, or in main memory or auxiliary storage of general computer 8; Central processing plant (1) to control the transmission, or to output the data in the storage device of the general computer (8) to the printer (9) or to read the data read out through the reading unit (2) to the printer (9) The buffer controller 10 is comprised.

Such a printer 9 can be configured for color printing, through which color data can be printed. On the other hand, in the case of using the color reading unit as the reading unit 2 can be used for color copying using a multifunction device.

In general, the printer 9 is a three-color printing system, which uses three colors of ink, cyan, magenta, and yellow, to print. That is, cyan (weak 'C' hereinafter), magenta (Magenta: `` M '' weak), yellow (Yellow: `` Y '' weak), cyan (C) and magenta (M) ) Through the combination of blue (Blue: weak 'B'), magenta (M) and yellow (Y), green (Green: 'G' weak), and cyan (C), magenta You can print seven color combinations of three colors: (M) and yellow (Y), which are black (Black: hereinafter abbreviated as 'B'). Print effect), you can print eight colors.

A general color halftone processing method in a three-color color printing system will be described with reference to FIG. 2.

First, the pixel of interest of the input color image is designated, and three colors of cyan, magenta, and yellow are separated (step: S1-1). Each pixel of the input color image is composed of three colors of R (red), G (green), and B (blue), and each color component is assumed to be 8 bits (256 gradations). At this time, cyan (C), magenta (M), yellow (Y) is obtained through the equation (1).

After color separation is completed in this way, error diffusion is applied to cyan, magenta, and yellow independently. That is, for cyan (C), a general error diffusion method is applied in step S1-2, and the target pixel value ti_c and 127 (half the maximum gray scale) modified in step S1-3 are compared to 127 or more. In this case, the cyan component (C) is set to 1 in step S1-4, and the cyan component (C) is set to 0 in step S1-5.

Here, the modified pixel value of interest means a new value in which the error of the peripheral pixel is added to the pixel value of interest by the error diffusion. In addition, a component of 1 means that the color component is printed at the position of the pixel of interest, and a component of 0 means that the color component is not printed at the position of the pixel of interest.

On the other hand, for magenta (M) and yellow (Y), each component is obtained through the steps S1-6 to S1-9 and S1-10 to S1-13 in the same manner.

The problem with printing in this three-color printing system is that the color of the three colors of cyan (C), magenta (M), and yellow (Y) colors overlap on the light background of the color document. It is distorted. That is, if three inks of cyan, magenta, and yellow overlap, the pixels are blue (when C and M overlap), red (when M and Y overlap), and green (Y And C overlapped), in which case the overlapped colors appear irregularly in the background, causing color distortion and image quality degradation.

Therefore, an object of the present invention is to prevent the ink quality of three colors of cyan (C), magenta (M), yellow (Y) are overprinted at the same time on the bright background portion and the print quality is distorted.

1 is a schematic block diagram of a general multifunction printer having a color printing portion,

2 is a flowchart illustrating a general color halftone processing method;

Figure 3 shows a color halftone treatment method for preventing ink overlap according to the present invention,

4 is a conceptual diagram illustrating binarization of one pixel of interest into cyan (C), magenta (M), yellow (Y) and synthetic image (C + M) according to the present invention.

According to the present invention for achieving the above object, a synthetic image (C + M) consisting of the sum of the turquoise (C) and magenta (M) is obtained and binarized to determine the background presence of the pixel of interest and the background of the pixel of interest In case of having a personality, the cyan (C) and magenta (M) components are set to 0, respectively, and binarized. When the pixel of interest does not have a background personality, the cyan and magenta (M) of the pixel of interest are determined. It is determined whether the sum of gradation values is less than or equal to a predetermined value, and when the sum is less than or equal to a certain value, the size of the modified pixel value ti_c of cyan and the modified pixel value ti_m of magenta M are compared. If the modified pixel of interest (ti_c) of cyan is larger than the modified pixel of interest (ti_m) of magenta (M), the cyan component (C) is set to 1, the magenta (M) component is set to 0, and the cyan ( The modified pixel of interest value ti_c of C) is equal to the modified pixel of interest value ti_m of magenta (M). If smaller, the cyan component (C) is set to zero and the magenta (M) component is set to one, and is binarized. When the sum of the grayscale values of the cyan (C) and magenta (M) exceeds the predetermined value, Disclosed is a color halftone processing method which prevents ink overlap which performs binarization for C) and magenta (M).

Hereinafter, the objects, features, and advantages of the present invention described above will be described in more detail with reference to the preferred embodiments of the present invention shown in the accompanying drawings.

The terms to be described below are terms defined in consideration of functions in the present invention, and may vary according to the intention or custom of a person skilled in the art, and the definitions should be made based on the contents throughout the specification.

Referring to Figure 3 looks at the color halftone processing method for preventing the ink overlap according to the present invention.

First, one pixel of the input color image is designated as the pixel of interest, and each color is separated from the pixel of interest consisting of three components of cyan (C), magenta (M), and yellow (Y) (step: S201). . Preferably, the pixel of interest is composed of three components, cyan, magenta, and yellow, as described above, and each component may consist of 8 bits (256 gradations).

After designating one pixel of the input image as the pixel of interest and dividing it into three color components, the error diffusion method is applied to the pixel of interest as cyan, magenta, yellow, yellow and y as shown in FIG. It binarizes each into a composite image (C + M) composed of a sum of cyan (C) and magenta (M) (steps S202 and S215).

In this case, the final diffusion is performed by applying the error diffusion method to the composite image (C + M), but only the operation of accumulating the errors by applying the error diffusion method to cyan and magenta (M) is performed. The determination is performed in steps S206 to S214 described later.

Subsequently, in step S203, it is determined whether the binarization result for the synthesized image C + M is the background (eg, the gradation value is 0). In this case, the binarization result of the composite image C + M is 0 or 255, where 0 is a background where ink is not taken and 255 is a portion where ink is taken.

As a result of determining whether the result of binarization of the synthesized image (C + M) is the background, if it is the background, the process moves to step S204, and the cyan (C) and magenta (M) components are all zero. That is, neither cyan (C) nor magenta (M) ink is printed at the position of the pixel of interest currently being processed.

If it is determined whether the result of binarization of the synthesized image (C + M) is the background, if it is not the background, the process proceeds to step S205 and checks whether the sum of the grayscale values of cyan (C) and magenta (M) is 255 or less. do. In this case, when the sum of each gray value is 255 or less, it means a bright background part. When the sum of gray values exceeds 255, it means that it is not a bright background part.

As a result of the inspection, if it is 255 or less, the process moves to step S06, and the size of the modified pixel value ti_c of cyan and the modified pixel value ti_m of magenta M are compared.

As a result of the comparison, if the modified pixel of interest (ti_c) of cyan is larger than the modified pixel of interest (ti_m) of magenta (M), the component of cyan is 1 and the component of magenta (M) is 0. (Step S207).

As a result of the comparison, if the modified pixel of interest (ti_c) of cyan is smaller than the modified pixel of interest (ti_m) of magenta (M), the component of cyan is zero and the component of magenta (M) is one. (Step S208). On the other hand, when the corrected pixel value ti_c of cyan and the corrected pixel value ti_m of magenta M are the same, steps S207 and S208 are applied alternately. This prevents overprinting of the cyan (C) and magenta (M) inks on a light background, thereby preventing distortion of the printed image.

If, as a result of the determination in step S205, if the sum of the respective gradation values of cyan (C) and magenta (M) exceeds 255, that is, an overflow of more than 8 bits occurs, step S209 and step S212 are performed. Move and independently binarize cyan (M) and magenta (M). That is, the cyan (C) is binarized in steps S210 to S211 by comparing the corrected pixel value ti_c of cyan (C) with 127 (half of the maximum gray scale) in step S209 with respect to cyan (C), and magenta The magenta M is binarized in steps S212 to S214 in the same manner as for the component (M).

On the other hand, as described above, yellow (Y) of the pixel of interest is binarized by applying the error diffusion method independently in step S215.

When all of these processes are completed, the process returns to the next pixel in step S216 and the above process is repeated until the processing for all the pixels of the input image is completed.

As described above, according to the present invention, by binarizing the composite image (C + M) composed of the sum of cyan (C) and magenta (M), the background pixel of the pixel of interest is determined by determining the background presence or absence of the pixel of interest. In case of having the cyan (C) and magenta (M) components, respectively, it is binarized by setting 0, and when the result of the C + M binarization is 255, the cyan (C + M) is less than 255 Since only one color is printed between the two and magenta (M), overlapping does not occur, so an even color image can be obtained.The value of the composite image (C + M) is 255 or less and cyan (C) and magenta (M). ), The color of the image is distributed evenly because yellow (Y) is less likely to overlap with cyan (C) and magenta (M) even in parts where the values of yellow (Y) are similar.

Accordingly, the ink of three colors of cyan (C), magenta (M), and yellow (Y) in the bright background portion of the color image is prevented from being overprinted simultaneously in the background portion to enable high quality color printing.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will appreciate that the present invention may be modified without departing from the spirit and scope of the invention as defined in the appended claims. It will be appreciated that modifications or variations may be made. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

Claims (4)

In the method of separating and binarizing cyan (C), magenta (M), and yellow (Y) from the pixel of interest, Binarizing the synthesized image (C + M) composed of a sum of cyan (C) and magenta (M) to determine the background presence of the pixel of interest; Binarizing each of the cyan (C) and magenta (M) components by setting the zero to zero when the pixel of interest has a background characteristic; When the result of the determination is that the pixel of interest does not have a background characteristic, it is determined whether the sum of the gradation values of the cyan and the magenta (M) of the pixel of interest is equal to or less than a predetermined value. The size of the modified pixel of interest (ti_c) and the size of the modified pixel of interest (ti_m) of magenta (M) so that the modified pixel of interest (ti_c) of cyan (C) becomes the modified pixel of interest of magenta (M). If it is larger than (ti_m), the cyan component (C) is set to 1 and the magenta (M) component is set to 0, and the corrected pixel value (ti_c) of cyan (C) is the modified pixel value (ti_m) of magenta (M). Less than) and binarizing the cyan (C) component to zero and the magenta (M) component to one; Inks comprising the cyan and magenta binarization steps that independently perform binarization for cyan (C) and magenta (M) when the sum of the respective grayscale values of cyan (C) and magenta (M) exceeds the predetermined value Collar halftone treatment method to prevent overlapping. The method of claim 1, wherein the cyan and magenta binarization step, A cyan binarizing step of binarizing the cyan color (C) by comparing the corrected pixel value (ti_c) of the cyan color (C) with a half value of the maximum gray scale with respect to the cyan color (C); Comprising a magenta digitizing step of binarizing the magenta (M) by comparing the corrected pixel value (ti_m) of the magenta (M) with the half value of the maximum gradation with respect to the magenta (M) to prevent the ink overlapping How to deal with a tank. The method of claim 1, wherein the constant value, A color halftone processing method for preventing ink overlap, characterized in that the maximum gradation value. The method of claim 1, The yellow (Y) of the pixel of interest further comprises the step of binarizing by applying an error diffusion method independently from the above steps.