Image processing device

Abstract

To perform density correction that considers the individual temporal changes of CMYK.SOLUTION: An image processing device includes: storage means that stores temporal degradation information for each combination of ink and recording medium; distinguishing means that distinguishes black character parts from parts other than black characters from read image data that has been read in color; elapsed time calculation means that calculates the temporal change by comparing the maximum density of the black character parts with temporal degradation information of K ink when it is determined that there are the black character parts, and calculates the temporal change on the basis of an identification image printed in yellow in a margin part when it is determined that there are no black characters; density correction transformation γ-curve generation means that generates a density correction transformation γ-curve for each CMYK ink from the degradation amount of the temporal change by drop count of each CMYK ink on the basis of the temporal change; and image correction means that corrects the image when printing on the basis of the density correction transformation γ-curve.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image processing apparatus that performs density correction taking into account the individual changes over time of CMYK. [Background technology]

[0002] The color tone (density, saturation) of printed matter fades over time. This tendency is particularly strong with inkjet ink. For this reason, in order to prevent fading, for example, printed matter may be stored in a clear file or other container that is not exposed to air, or in a constant temperature and humidity room. However, after a certain amount of time has passed, the color balance of the printed matter may appear strange. This is because the inks of each color, CMYK, do not change over time in the same way, and there are variations in the degree of fading.

[0003] In addition, paper exposed to ultraviolet light (from sunlight or electric lights that emit ultraviolet light) changes the white of the paper, turning it yellowish, and yellow and magenta inks in particular fade. Taking these factors into consideration, in order to maintain a stable color, paper should be stored in an environment with constant temperature and humidity, away from air and ultraviolet light, but it is not realistic for ordinary users to have such an environment.

[0004] Patent Document 1 proposes a correction process that increases the image density of the original image data when it is read. Patent Document 2 also proposes a function that reads the result of printing a fixed pattern with an image scanner, calculates the difference between the density of the print result and the density of the fixed pattern, and corrects the print density based on this density difference. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-142274 A [Patent Document 2] Japanese Patent Application Publication No. 7-333930 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, correction processing is performed to increase the image density of the original image data when it is read, but since it only supports color material saving processing that limits the amount of color material consumed, it does not provide density correction that takes into account the individual changes over time of CMYK. Also, in Patent Document 2, the result of printing with a fixed pattern is read by an image scanner, the difference between the density of the print result and the density of the fixed pattern is calculated, and the print density is corrected based on this density difference, but like Patent Document 1, it does not provide density correction that takes into account the individual changes over time of CMYK.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide an image processing apparatus that performs density correction taking into consideration the individual changes over time of CMYK. [Means for solving the problem]

[0008] In order to achieve the above object, the image processing device according to the present invention is characterized by: A storage means for storing information on deterioration over time for each combination of ink and recording medium; A discrimination means for discriminating between black text and non-black text from the read image data read in color; an aging time calculation means for calculating a change over time by comparing a maximum density of the black character portion with the time deterioration information of the K ink when the discrimination means discriminates that a black character portion is present, and for calculating a change over time based on an identification image printed in yellow in a margin portion when the discrimination means discriminates that no black character portion is present; a density correction conversion gamma curve generating means for generating a density correction conversion gamma curve for each of the CMYK inks from the deterioration amount of the change over time for each drop number of the CMYK inks based on the change over time calculated by the time calculation means; an image correction means for correcting an image when printed based on the density correction conversion γ curve generated by the density correction conversion γ curve generation means; The reason is that it is equipped with the following features. Effect of the Invention

[0009] According to the features of the image processing apparatus of the present invention, it is possible to perform density correction taking into consideration the changes over time of each of CMYK. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of an inkjet printing apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a functional configuration diagram of an image processing unit included in the inkjet printing apparatus of the present embodiment. [Diagram 3] 3 is an explanatory diagram for explaining a schematic diagram of a process in an image processing unit provided in the inkjet printing apparatus of the present embodiment. FIG. [Figure 4] 1A is a diagram showing an example of time-dependent change data by drop number for each CMYK ink generated by an aging time calculation section, and FIG. 1B is a diagram showing an example of a density correction conversion gamma curve for each CMYK ink generated by a density correction conversion gamma curve section. [Diagram 5] 11 is an explanatory diagram illustrating generation of a density correction conversion gamma curve by a density correction conversion gamma curve section. FIG. [Figure 6] 6 is a flowchart showing the process content of a pre-processing operation in the inkjet printing apparatus of the present embodiment. [Figure 7] 6 is a flowchart showing the process of a preliminary correction operation in the inkjet printing apparatus of the present embodiment. [Figure 8] 6 is a flowchart showing the process of a preliminary correction operation in the inkjet printing apparatus of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings. However, it should be noted that the drawings are schematic and may differ from the actual product. In addition, the drawings may include parts with different dimensional relationships and ratios.

[0012] The embodiments described below are merely examples of devices for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the arrangement of each component to that described below. Various modifications can be made to the technical idea of ​​the present invention within the scope of the claims.

[0013] An inkjet printing apparatus using an embodiment of an image processing apparatus of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a schematic diagram of an inkjet printing apparatus 1 of this embodiment.

[0014] The inkjet printing apparatus 1 of this embodiment is connected to a computer 2 and a scanner 3 .

[0015] The computer 2 is a processing unit equipped with a CPU, and has the function of creating image data for printing using various application software and instructing the execution of printing processing of the image data. The computer 2 can be realized, for example, by a general-purpose computer such as a personal computer, or a dedicated device with specialized functions.

[0016] The scanner 3 irradiates light from a light source onto an original on which an image is printed and placed on an original table, and obtains color image data by reading the reflected light from the exposed surface with a CCD.

[0017] The inkjet printing device 1 performs printing processing by ejecting ink from nozzles (ejection units) onto a sheet-like printing medium such as paper or film based on input image data. As shown in FIG. 1, the inkjet printing device 1 includes an image processing unit 21, a head drive control unit 22, an inkjet head unit 23, a transport unit 24, and a control unit 25.

[0018] The image processing unit 21 acquires image data output from the computer 2 or image data output by reading an original image with the scanner 3, and performs various processes on the image data. The image processing unit 21 includes a CPU (Central Processing Unit) and a semiconductor memory. The image processing unit 21 executes a program stored in advance in a storage medium such as the semiconductor memory or a hard disk, and operates electric circuits to perform processes for each unit described later. Details will be described later.

[0019] The head drive control unit 22 drives the inkjet head unit 23 to eject ink from each nozzle of the inkjet head of each color based on drop data for each color generated by the image processing unit 21 to be ejected from the nozzles (ejection units).

[0020] The inkjet head unit 23 includes a plurality of inkjet heads that eject ink of each color of C, M, Y, and K. As described above, each inkjet head is controlled by the head drive control unit 22 based on the drop data of each color to eject ink onto the printing medium, thereby forming a print image on the printing medium.

[0021] The transport unit 24 includes a transport mechanism that transports the print medium to the inkjet head unit 23 .

[0022] The control unit 25 includes a CPU (Central Processing Unit) and a semiconductor memory, and controls the entire inkjet printing apparatus 1. The control unit 25 executes a control program stored in advance in a storage medium such as the semiconductor memory or a hard disk, and controls the operation of each part of the inkjet printing apparatus 1 by operating an electric circuit.

[0023] FIG. 2 is a functional configuration diagram of the image processing unit 21 included in the inkjet printing apparatus 1 of this embodiment.

[0024] As shown in FIG. 2, the image processing unit 21 includes an image data receiving unit 30, a discrimination unit 31, an elapsed time calculation unit 33, a density correction conversion gamma curve unit 34, an image correction unit 35, a preprocessing unit 36, and a memory unit 37.

[0025] The pre-processing unit 36 ​​performs pre-processing according to the image data and prints it. Specifically, the pre-processing unit 36 ​​judges whether or not the acquired image data has a solid black character portion (100% black). If it is judged that there is no solid black character portion (100% black), the pre-processing unit 36 ​​acquires the model, paper, printing date and time, etc. from, for example, header information of the acquired image data, and flags (converts to a two-dimensional code) the acquired model, paper, printing date and time, etc. to generate a two-dimensional code.

[0026] Then, the pre-processing unit 36 ​​converts the color of the generated flag (two-dimensional code) to yellow, which is inconspicuous when printed, and supplies the image data including the flag (two-dimensional code) converted to yellow to the head drive control unit 22, which then prints it.

[0027] On the other hand, if it is determined that there is a solid black character portion (100% black), the preprocessing unit 36 ​​supplies the image data received by the image data receiving unit 30 to the head drive control unit 22, which then causes it to be printed.

[0028] The storage unit 37 stores information on deterioration over time for each combination of ink and recording medium.

[0029] The image data receiving unit 30 receives image data.

[0030] The discrimination unit 31 discriminates between black text and non-black text from image data read in color.

[0031] When the discrimination unit 31 determines that there is a black character portion, the elapsed time calculation unit 33 calculates the elapsed time by comparing the maximum density of the black character portion with information on deterioration over time of the K ink stored in the memory unit 37, which will be described later. When the discrimination unit 31 determines that there is no black character, the elapsed time calculation unit 33 calculates the elapsed time based on a flag (two-dimensional code) printed in yellow in the margin portion.

[0032] 3 is an explanatory diagram that illustrates the process in the image processing unit 21 included in the inkjet printing apparatus 1 of this embodiment. Image data G101 shown in Fig. 3 is image data that has a black character portion, and image data G111 is image data that does not have a black character portion.

[0033] 3, image data G101 is image data that includes a black character portion, so aging time calculation unit 33 generates image data G102 from which the black character portion is extracted. Then, aging time calculation unit 33 obtains aging change data D100 by comparing the maximum density of the black character portion with aging deterioration information of K ink stored in storage unit 37, which will be described later, and uses this to calculate a deterioration density difference. Details will be described later.

[0034] On the other hand, image data G111 does not have a black character portion, i.e., it includes a flag (two-dimensional code) G111a converted to yellow. Therefore, discrimination unit 31 converts the copied image data to gray to generate image data G112, and binarizes the generated gray image data to generate image data G113.

[0035] Then, the elapsed time calculation unit 33 extracts a flag (two-dimensional code) G113a printed in yellow in the margin from the generated image data G113, obtains change-over-time data D100 based on this flag (two-dimensional code) G113a, and calculates the deterioration concentration difference from this.

[0036] A density correction conversion gamma curve section 34 generates a density correction conversion gamma curve for each CMYK ink from the deterioration amount of the change over time for each drop number of each CMYK ink based on the change over time data calculated by the elapsed time calculation section 33 .

[0037] FIG. 4(a) is a diagram showing an example of time-dependent change data by drop number for each CMYK ink generated by the time-elapsed calculation unit 33, and FIG. 4(b) is a diagram showing an example of density correction conversion gamma curves for each CMYK ink generated by the density correction conversion gamma curve unit 34.

[0038] As shown in Fig. 4(a), the elapsed time calculation unit 33 generates data on the change over time by the number of drops for each of the CMYK inks. The data D101 on the elapsed time shown in Fig. 4(a) is data showing the change over time in the OD (Optical Density) value when the maximum number of six drops is ejected for each of the CMYK inks.

[0039] The density correction conversion gamma curve unit 34 generates density correction conversion gamma curves for each of the CMYK inks shown in Fig. 4(b) based on the time-varying data shown in Fig. 4(a). The density correction conversion gamma curve D201 shown in Fig. 4(b) indicates RGB values ​​relative to the number of drops of K (black) ink.

[0040] FIG. 5 is an explanatory diagram for explaining generation of a density correction conversion gamma curve by the density correction conversion gamma curve section 34. As shown in FIG.

[0041] 5, the horizontal axis of the density correction conversion gamma curve D201 is converted from 0 to 6 drops into RGB values ​​of 0 to 255. The vertical axis of the density correction conversion gamma curve D201 is converted into RGB values ​​of 255 with the maximum K (black) density immediately after printing taken as 100%.

[0042] The maximum density of K (black) during scanning is shown in D201b.

[0043] The density correction conversion gamma curve unit 34 sets the difference ratio between the maximum density D201b of K (black) when scanning one drop and the density immediately after printing as D11, and sets the plot point P11 of the ink correction gamma. Similarly, the density correction conversion gamma curve unit 34 sets the difference ratios between the maximum density D201b of K (black) when scanning two to six drops and the density immediately after printing as D12 to D16, and sets the plot points P12 to P16 of the ink correction gamma.

[0044] The density correction conversion gamma curve unit 34 calculates an approximation curve of each of the plot points P11 to P16 and generates it as a density correction conversion gamma curve D201a.

[0045] The image correction section 35 corrects the image when it is printed, based on the density correction conversion gamma curve generated by the density correction conversion gamma curve section 34.

[0046] (Operation of the inkjet printing device) FIG. 6 is a flow chart showing the process contents of the pre-processing operation in the inkjet printing apparatus 1 of this embodiment.

[0047] As shown in FIG. 6, in step S101, the preprocessing unit 36 ​​stores information on the change over time in density by drop number for each of the CMYK inks for each model of the inkjet printing device 1 and for each paper.

[0048] If it is determined in step S103 that the function of correcting changes over time is present (YES), in step S105, the preprocessing unit 36 ​​acquires image data.

[0049] In step S107, the preprocessing unit 36 ​​determines whether or not the acquired image data includes a black character portion (100% black).

[0050] If it is determined that there is no solid black text portion (100% black) (step S107; NO), in step S109, the pre-processing unit 36 ​​acquires the model, paper, printing date and time, etc. from, for example, header information of the acquired image data.

[0051] In step S111, the pre-processing unit 36 ​​converts the acquired model, paper, printing date and time, etc. into a flag (two-dimensional code) and generates a three-dimensional code.

[0052] In step S113, the pre-processing unit 36 ​​converts the color of the generated flag (two-dimensional code) into yellow, which is inconspicuous even when printed.

[0053] In step S115, the pre-processing unit 36 ​​prints the image data. Specifically, the pre-processing unit 36 ​​supplies the image data including the flag (two-dimensional code) converted to yellow to the head drive control unit 22, and causes it to print.

[0054] If it is determined in step S107 that there is a black character portion (100% black) (step S107; YES), in step S121, the pre-processing unit 36 ​​supplies the to the head drive control unit 22 to cause printing.

[0055] 7 and 8 are flow charts showing the processing contents of the preliminary correction operation in the inkjet printing apparatus 1 of this embodiment.

[0056] As shown in FIGS. 7 and 8, in step S201, the scanner 3 acquires image data by performing CMYK color scanning from a light source on an original on which an image is printed and placed on an original table.

[0057] In step S203, the discrimination unit 31 stores the scanned image data.

[0058] In step S205, the discrimination unit 31 copies the scanned image data.

[0059] In step S207, the discrimination unit 31 converts the copied image data into gray.

[0060] In step S209, the discrimination unit 31 converts the gray image data into a binary value.

[0061] In step S211, the discrimination unit 31 determines whether or not a three-dimensional code is present in the binarized image data.

[0062] If it is determined that the binarized image data contains a two-dimensional code (step S211; YES), since the original image data does not contain black text (100% black), in step S213, the elapsed time calculation unit 33 extracts the model, paper, printing date and time, etc. from the two-dimensional code contained in the image data.

[0063] On the other hand, if it is determined that the binarized image data does not contain a two-dimensional code (step S211; NO), the original image data contains a black character portion (100% black), so in step S215, the elapsed time calculation unit 33 extracts the black character portion from the image data.

[0064] In step S217, the elapsed time calculation unit 33 calculates the maximum density within the extracted black character.

[0065] In step S219, the elapsed time calculation unit 33 compares the information on the change over time at the maximum drop of K ink (black ink) stored in the storage unit 37 with the density of the extracted black character portion to determine the printing date and time.

[0066] In step S221, the elapsed time calculation unit 33 calculates the original (immediately after printing) density of each of the CMYK inks from the determined printing date and time of the K ink.

[0067] In step S223, the density correction conversion gamma curve unit 34 calculates the density difference (correction value) for each drop of each of the CMYK inks.

[0068] In step S225, the density correction conversion γ curve unit 34 generates a correction calculation γ curve from the drop-by-drop density differences (correction values) of each of the CMYK inks.

[0069] In step S227, the image correction unit 35 corrects the C component of the image data to gamma data.

[0070] In step S229, the image correction unit 35 corrects the M component of the image data to gamma data.

[0071] In step S231, the image correction unit 35 corrects the Y component of the image data to gamma data.

[0072] In step S233, the image correction unit 35 corrects the K component of the image data to gamma data.

[0073] In step S235, the density correction conversion gamma curve unit 34 determines whether or not there is a paper white density difference in the corrected image data.

[0074] If it is determined that the corrected image data has a paper-white density difference (step S235; YES), in step S237, the density correction conversion γ curve unit 34 generates a paper-white density correction γ. Here, the paper-white density correction refers to a correction that increases the density of Y (yellow) and M (magenta) by a predetermined amount.

[0075] In step S239, the image correction unit 35 generates image data after paper white density correction.

[0076] In step 241, the image processing unit 21 determines, based on a user input, whether to scan (copy and print) or store the generated image data.

[0077] When scanning (copying and printing) (step S241; scanning (copying and printing)), the image processing unit 21 causes printing based on the corrected image data.

[0078] On the other hand, if the image is to be stored (step S241; store), the image processing unit 21 causes the storage unit 37 to store the corrected image data.

[0079] In this embodiment, six drops are ejected as the maximum number of drops for each of the CMYK inks, but the maximum number of drops is not limited to six drops and may be different depending on the paper.

[0080] In addition, in the present embodiment, a two-dimensional code is given as an example of the flag, but the flag is not limited to this and various bar codes may be used.

[0081] Furthermore, in this embodiment, an example has been described in which the inkjet head unit 23 ejects CMYK inks, but this is not limited to this, and inks of other colors, such as Gy (gray), may also be ejected in addition to CMYK.

[0082] (Additional Note) This application discloses the following inventions.

[0083] (Appendix 1) A storage means for storing information on deterioration over time for each combination of ink and recording medium; A discrimination means for discriminating between black text and non-black text from the read image data read in color; an aging time calculation means for calculating a change over time by comparing a maximum density of the black character portion with the time deterioration information of the K ink when the discrimination means discriminates that a black character portion is present, and for calculating a change over time based on an identification image printed in yellow in a margin portion when the discrimination means discriminates that no black character portion is present; a density correction conversion gamma curve generating means for generating a density correction conversion gamma curve for each of the CMYK inks from the deterioration amount of the change over time for each drop number of the CMYK inks based on the change over time calculated by the time calculation means; an image correction means for correcting an image when printed based on the density correction conversion γ curve generated by the density correction conversion γ curve generation means; An image processing device comprising:

[0084] This makes it possible to perform density correction that takes into account the changes over time of each CMYK color, so that even if the color tone (density, saturation) of the printed material deteriorates over time, such as fading, it is possible to print in the appropriate color. [Explanation of symbols]

[0085] 1 Inkjet printing device 2. Computer 3. Scanner 21 Image processing section 22 Head drive control unit 23 Inkjet head unit 24 Conveyor 25 Control Unit 30 Image data reception section 31 Discrimination part 33 Elapsed time calculation unit 34 Density correction conversion gamma curve generation unit 35 Image correction section 36 Pretreatment section 37 Memory section

Claims

[Claim 1] A storage means for storing information on deterioration over time for each combination of ink and recording medium; A discrimination means for discriminating between black text and non-black text from the read image data read in color; an aging time calculation means for calculating a change over time by comparing a maximum density of the black character portion with the time deterioration information of the K ink when the discrimination means discriminates that the black character portion is present, and for calculating a change over time based on an identification image printed in yellow in a margin portion when the discrimination means discriminates that the black character portion is not present; a density correction conversion gamma curve generating means for generating a density correction conversion gamma curve for each of the CMYK inks from the deterioration amount of the change over time for each drop number of the CMYK inks based on the change over time calculated by the time calculation means; an image correction means for correcting an image when printed based on the density correction conversion γ curve generated by the density correction conversion γ curve generation means; An image processing device comprising:

Images