JP2006165711A - Image processing method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing method and an image forming apparatus capable of preventing the print quality from being deteriorated in the case of using a composite color. <P>SOLUTION: When the residual amount of a pure black color material is small, the image forming apparatus carries out image processing as shown in the following. When target pixels are character data or monochromatic image data, it is highly possible that pixels 602 to 605 are (Y, M, C) = (FF, FF, FF ) or (0, 0, 0), and the data are printed in the pure black. When the target pixels are color image data, it is highly possible that the pixel data within a range of 602 to 605 are other than (Y, M, C) = (FF, FF, FF ), then the data are printed in a process black. Through the control above, the pure black whose residual amount is small can efficiently be used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing method and an image forming apparatus that perform printing while detecting the remaining amount of consumables in color printing and considering the remaining amount.

  Recently, ink jet printers have become widespread. This ink jet printer holds a plurality of colors of ink. By overprinting the plurality of colors of ink while adjusting the discharge amount, it is possible to print a color image with many colors. The plurality of colors mainly include color materials of yellow (Y), magenta (M), and cyan (C), which are the three primary colors of additive color mixing.

  Further, black (K, pure black) is often mounted on recent ink jet printers. Black (process black) can be expressed as a composite color by mixing the three YMC colors, but by retaining black (pure black) ink, color development is improved, and bleeding due to large amounts of ink being applied Effects such as prevention and reduction of the total ink consumption can be obtained.

  However, on the other hand, it is effective to use a composite color (process black) in order to efficiently use consumables or for an emergency. For example, when the color ink and pure black ink tanks are integrated, it is useless to discard the ink tank because the pure black ink is exhausted even though there is sufficient color ink. In that case, mixing three colors and printing black (process black) is effective for efficient use of consumables.

Even if the tanks for color ink and pure black ink are separate types, there is a means to print with process black when there is no pure black ink to replace but there is no pure black ink to replace and there is an urgent need to print. Conceivable. Thus, it is very effective to have a printing means using process black.
JP 2001-121753 A

  However, the use of process black has the problem that the print quality deteriorates, such as the black density becoming lighter and the outline of black characters blurring.

  Therefore, a control method for expressing black by using process black has been devised. As one of the control methods, it has been proposed as in Patent Document 1. According to this patent, monochrome printing can be performed at a designated location by setting the start and end positions of monochrome printing and controlling printing.

  However, the conventionally proposed method requiring setting as described above is complicated. This method places a heavy burden on the user when printing a large amount of print data or print data having a complicated configuration where a monochrome print is desired.

  The present invention solves the above-described problems of the prior art in an image forming apparatus that performs color printing. Even when process black is used, pure black is used for a monochrome printing portion by automatic processing. Accordingly, an object of the present invention is to provide a specific image processing method and an image forming apparatus capable of printing without reducing image quality as much as possible.

  In order to achieve this object, the image forming apparatus according to the present invention has the following functions.

  This image forming apparatus is an image forming apparatus that includes a plurality of storage units each storing a plurality of color materials, a remaining amount detection unit, and an image processing unit, and detects the remaining amount of each color material prior to a printing operation. The image processing method is changed according to the detected remaining amount, and printing is performed.

  The following means are used as a printing control method. When the black color material reaches an arbitrarily determined threshold value in the remaining amount detection unit, if there is sufficient CMY three-color ink, the normal print mode is switched to the process black print mode. Processing in the process black printing mode is performed as follows. When the information that black is printed in the area to be processed is sent and the area around the area to be processed is black data or white data, the data is character data or monochrome There is a high possibility that it is image data.

  Therefore, this area is printed with pure black. By doing so, the black density can be increased and controlled so as not to bleed. When the area around the area is other than black data or white data, it is highly possible that the area is color image data, so printing is performed with process black. This makes it possible to minimize degradation of image quality even when using process black.

  According to the present invention, process black is used for color image data even when control using process black is performed because the remaining amount of pure black is reduced, but in the case of character data or monochrome image data, pure black is used. Print using. By performing the control according to the present invention, it is possible to minimize degradation of image quality even when using process black.

  Embodiments of the present invention will be described below.

(First embodiment)
Processing at Black Generation FIG. 1 is a configuration diagram of a control circuit that detects the remaining amount and controls the printing method by means of the present invention. In the figure, reference numeral 101 denotes a host unit that transmits and receives commands and image data to a printer control circuit unit described later. A printer control circuit unit 102 controls the printer. Reference numeral 103 denotes a print head. There are as many heads as there are printable color materials. Further, this head is provided with a color material remaining amount detection unit 104 such as a sensor for detecting the remaining amount of color material.

  The printer circuit control unit 102 includes a CPU 106 that performs overall control of the printing operation, an interface unit 107 that inputs and outputs data with the host unit 101, a ROM 108 that stores a program that controls the printer, and a memory that can read and write data. The RAM 109 that holds image data and data relating to the remaining amount of color material, the head control unit 110 that transmits the print operation and print data to the head 103, and the information from the color material remaining amount detection unit 104 provided in the head 103. It comprises an input color material remaining amount detection control unit 111 and an image processing unit 114 that performs image processing. Here, the image processing unit is not necessarily required if there is another means to replace the image processing means.

  The color material remaining amount detection unit includes the following means. Measuring the weight of the color material storage with a sensor and detecting the remaining amount, Method of physically detecting the color material in the storage with an optical sensor, Change in inductance using electrodes provided in the color material storage A method of detecting the remaining amount by measuring the color material consumption amount, or the like is used.

  FIG. 2 is a block diagram showing an image processing procedure according to the present invention. Each component will be described below.

  <Input γ Correction> γ correction is performed so that the input RGB signal matches the output characteristics of the device. The corrected signals are Rg, Gg, and Bg.

  <LOG conversion> RGB data is converted into CMY data. The relationship between luminance and density is logarithmic, and this conversion is obtained by the following calculation.

Y1 = -log (Bg)
M1 = -log (Gg)
C1 = −log (Rg)

  <Masking> CMY data is corrected. This is calculated by a 3 × 3 primary transformation.

_{Y2 = m 11 × Y1 + m} 12 × M1 + m 13 × C1
_{M2 = m 21 × Y1 + m} 22 × M1 + m 23 × C1
C2 = m ₃₁ × Y1 + m ₃₂ × M1 + m ₃₃ × C1
<Black generation> In the input YMC data of (Y2, M2, C2), when expressing black, it is expressed in a state of mixing three colors (FF, FF, FF). By replacing this black with pure black, the black density is stabilized and the total ink consumption can be suppressed. Black generation is an operation of replacing the input YMC with black.

  For example, black generation is performed as follows. Of the three colors (Y2, M2, C2) masked in step 203, the lowest density is set as the black density. The difference of this black density is taken from the density of the YMC three colors and replaced with black data. As shown in FIG. 3, when (Y, M, C) = (45, C5, 6A), the mixed amount of the three colors is replaced with black ink. Then, (Y3, M3, C3, K3) = (0, 80, 25, 45). Many image forming apparatuses holding pure black ink usually perform this processing. The present invention relates to the control of this processing. The control method will be described later.

  <Output γ conversion> The density of the input and the amount of ink actually applied do not generally match, and are largely due to the characteristics of the ink. This is conversion for correcting the density and the amount of ink actually hit.

  <Binarization Processing> Inkjet printers hit ink dots on media. The density of the image is expressed by densely distributing the dots, thereby expressing the image. The dots are printed with the information that they do not strike. The binarization process is a process of converting this dot into information indicating whether or not to strike.

  A basic processing operation executed by the CPU 106 will be described. FIG. 4 is a flowchart showing the print mode switching procedure. In this embodiment, printing is performed in the normal print mode when the remaining amount of the color material is sufficient. If the remaining amount of black color material is less than a certain threshold value and if CMY ink is sufficient, the process black print mode is switched. The processing procedure will be described.

In step S401, the remaining amount of each color material is detected prior to printing. Then, in S402, it is compared whether or not the remaining amount of black ink K is greater than a certain threshold value (m _k ). This threshold is arbitrarily determined by the designer. This threshold value is based on, for example, the print size or application of the printer. If the remaining amount of black ink is greater than or equal to the threshold value, the process proceeds to S403. In step S403, the printer performs normal printing, and the printing operation ends. If the remaining amount of black ink is equal to or less than the threshold value in S402, the process proceeds to S404. In S404, it is determined whether the remaining amount of each of the yellow (Y), magenta (M), and cyan (C) inks is sufficient. Although this determination method can be arbitrarily determined, it is preferable to determine based on the threshold value m _k such as two to several times the threshold value m _k of black ink from the viewpoint of printing pure black with process black. If the remaining amount of YMC ink is insufficient, it is determined that there is not enough YMC to print process black.

  In step S403, normal printing is performed. If the remaining amount of YMC ink is sufficient, the process proceeds to S405 to enter the process black printing mode. In the process black print mode processing in S405, control is performed to efficiently use the remaining black ink. Details of the processing in the process black printing mode will be described with reference to FIG. Here, when proceeding to the process black printing mode, as described in claim 9, there may be provided means for notifying the user that the process black is used. Further, as described in claim 10, after notifying the user that the process black is to be used, a means for determining the user's intention may be provided.

  FIG. 5 is a diagram showing a processing order when printing an image in this embodiment. Reference numeral 501 represents the entire range of the image, and 502 represents each pixel constituting the image. In this embodiment, the unit of the area to be processed is a pixel as in claim 5. As shown by the arrows in this figure, the first row is subjected to image processing sequentially from the left. When the processing for one row is completed, the image processing is performed in order from the left in the same manner as the processing for the second row. Thereafter, similarly, processing is performed up to the last line.

  When processing is performed in the order shown in FIG. 5 as in the present embodiment, when a certain pixel is processed, FIG. 6 shows pixels that have already been processed among the periphery of the pixel. . Reference numeral 601 denotes a pixel to be processed. Reference numerals 602 to 605 are ranges in which processing has already been completed when processing 601.

  In the process black printing mode, processing is performed as follows. If the target pixel is character data or monochrome image data, the pixels 602 to 605 are (Y, M, C) = (FF, FF, FF) or (0, 0, 0). Is likely. If the target pixel is color image data, the pixel data in the range of 602 to 605 is likely to be other than (Y, M, C) = (FF, FF, FF). Therefore, if 602 to 605 are (Y, M, C) = (FF, FF, FF) or (0, 0, 0), printing is performed in pure black. If 602 to 605 are other than (Y, M, C) = (FF, FF, FF), printing is performed with process black. By performing this control, the remaining pure black can be used efficiently.

  The diagram shown in FIG. 6 showing a pixel to be referred to when a certain pixel is processed is not considered with respect to pixel data at the end in the image. FIG. 7 is a diagram illustrating pixels referred to when processing pixel data at an end in an image. (A) When processing the pixel data 710 at the upper left end in the image, there is no pixel data to be referred to, so normal processing may be performed. (B) When processing the pixel data 720 at the upper end, the pixel data 721 in the figure is referred to. (C) When processing the pixel data 730 at the upper right end, the pixel data 731 in the figure is referred to. (D) When processing the pixel data 740 at the left end, reference is made to the pixel data 741 and 742 in the figure. (E) When processing pixel data 750 that is not in contact with the end, reference is made to pixel data 751 to 754 in the figure. (F) When processing the pixel data 760 on the right end, reference is made to the pixel data 761 to 763 in the figure. (G) When processing the pixel data 770 at the lower left corner, reference is made to the pixel data 771 and 772 in the figure. (H) When processing pixel data 780 at the lower end, reference is made to pixel data 781 to 784 in the figure. (I) When processing the pixel data 790 at the lower right end, the pixel data 791 to 793 in the figure are referred to.

  In this embodiment, the range to be referred to when a certain pixel is processed is shown in FIG. 6, but when the processing order is different from the method described in this embodiment (for example, in the column direction or in the row direction over a plurality of rows). Even in the case of processing), the processing is not limited to the range of FIG. 6 as long as the previously processed data is referenced when processing a certain pixel. In addition, if the previously processed data is referenced when processing a certain pixel, the range may be expanded without being limited to the range of FIG.

  In this embodiment, the unit to be processed is a pixel. However, when the present invention is carried out, an arbitrary area may be used instead of a pixel unit.

(Second embodiment)
Processing before RGB conversion In the first embodiment, the process black is controlled at the time of black generation after conversion to YMC. In the second embodiment, the present invention is implemented before image processing of RGB signals. . By adopting this control method, it is decided whether black data is printed with pure black or process black before image processing, and therefore unnecessary image processing is not performed, so that the processing speed can be increased.

  A configuration diagram, a block diagram of image processing, and a chart in the second embodiment are the same as those in the first embodiment. In the second embodiment, control is performed as follows.

  When the amount of pure black ink decreases and there is sufficient YMC ink, the process black print mode is similarly switched. In this process black printing mode, the following processing is performed.

  In FIG. 6, if the target pixel is character data or monochrome image data, the pixels 602 to 605 are (R, G, B) = (0, 0, 0) or (FF, FF, FF). If the target pixel is color image data, the pixel data in the range of 602 to 605 is likely to be other than (R, G, B) = (0, 0, 0). Therefore, if 602 to 605 are (R, G, B) = (0, 0, 0) or (FF, FF, FF), printing is performed in pure black. If 602 to 605 are other than (R, G, B) = (0, 0, 0), printing is performed with process black. By performing this control, the remaining pure black can be used efficiently.

(Third embodiment)
Processing in a system that processes data separately Among image processing systems, there is a system that processes character data and image data separately. Examples of the present invention will be given in the system.

  FIG. 8 is a block diagram showing image processing in the present embodiment. Each processing content is the same as the method in FIG. 3 in the first embodiment. In this embodiment, the processing of 801 and 802 is performed on the host side, and the processing of 803 to 806 is performed on the image forming apparatus side. However, the execution processing may be performed by either. Character data is processed separately from image data.

  The image data is sent to the image forming apparatus as CMY multi-value data. Character data is sent to the image forming apparatus as binary data. The CMY multilevel data is subjected to normal conversion in the black generator. When pure black (K) is reduced and there are sufficient CMY three-color inks, printing is performed with process black. However, the binary data sent to the image forming apparatus is printed with pure black. With the above processing, in the process black printing mode, process data is used for black data in image data, and pure black is used for character data.

It is a block diagram which shows the structure of 1st Example of this invention. 5 is a flowchart illustrating a printing mode switching procedure in the first embodiment. It is a figure of description of black production | generation in 1st Example. It is a block diagram which shows the image processing procedure in 1st Example. It is a figure which shows the process order which prints an image in 1st Example. It is a figure which shows the pixel referred at the time of the process of a certain pixel in 1st Example. It is a figure which shows the pixel referred at the time of the process of a certain pixel in 1st Example. It is a block diagram which shows image processing in 3rd Example.

Explanation of symbols

101 Host unit 102 Printer control circuit unit 103 Head 104 Color material remaining amount detection unit 106 CPU
107 Interface unit 108 ROM
109 RAM
110 Head control unit 111 Color material remaining amount detection control unit 114 Image processing unit

Claims (13)

In the image processing method,
An image processing method comprising a control method for determining an image processing method by referring to another region when processing a certain region. In the image processing method,
The image processing method according to claim 1, further comprising a control method for determining an image processing method with reference to an already processed area. In the image processing method,
3. The image processing method according to claim 1, further comprising a control method for determining an image processing method with reference to an area close to the area. In the image processing method,
The image processing method according to claim 1, wherein an area to be processed is a pixel unit. In an image forming apparatus including a plurality of storage units that respectively store yellow, magenta, cyan, and pure black color materials,
5. An image forming apparatus comprising: a control unit that controls printing of pure black and process black by the image processing method according to claim 1. In an image forming apparatus comprising: a plurality of storage units that respectively store yellow, magenta, cyan, and pure black color materials; and a remaining amount detection unit that detects a remaining amount of each color material.
Prior to the printing operation, the remaining amount of each color material is detected, and when the remaining amount of the pure black color material is less than or equal to the threshold value, pure black and process black printing are controlled by the image processing method according to claim 1 An image forming apparatus comprising a control unit. In an image forming apparatus including a plurality of storage units each storing yellow, magenta, cyan, and pure black color materials, and an image processing method for separately processing image data and character data,
An image forming apparatus comprising a control means for controlling printing of pure black and process black by the image processing method according to claim 1. A plurality of storage units respectively storing yellow, magenta, cyan, and pure black color materials; a remaining amount detection unit that detects the remaining amount of each color material; and an image processing method that separately processes image data and character data. In the image forming apparatus provided,
Prior to the printing operation, the remaining amount of each color material is detected, and when the remaining amount of the pure black color material is equal to or less than the threshold value, pure black and process black printing are controlled by the image processing method according to claim 1. An image forming apparatus comprising a control unit. In the image forming apparatus,
When the remaining amount of pure black color material is less than or equal to the threshold, after confirming that the remaining amount of yellow, magenta, and cyan is greater than a certain threshold, change the image processing method, and control means to print with process black The image forming apparatus according to claim 6, further comprising: In the image forming apparatus,
The image forming apparatus according to claim 9, further comprising a control unit that performs control to determine threshold values of yellow, magenta, and cyan based on a threshold value of a remaining amount of pure black color material. In the image forming apparatus,
The image forming apparatus according to claim 6, further comprising notification means for notifying a user. In the image forming apparatus,
12. The image forming apparatus according to claim 11, further comprising a control unit that notifies a user by the notification unit when changing an image processing method. In the image forming apparatus,
13. The image forming apparatus according to claim 12, further comprising a control for notifying the user by the notifying means when changing the image processing method and controlling the execution of printing according to the user's intention.