WO2023078304A1

WO2023078304A1 - Spray head compensation method based on binary image

Info

Publication number: WO2023078304A1
Application number: PCT/CN2022/129291
Authority: WO
Inventors: 刘志红; 陈�峰; 樊浩力
Original assignee: 北京大学
Priority date: 2021-11-04
Filing date: 2022-11-02
Publication date: 2023-05-11
Also published as: CN114211882B; CN114211882A

Abstract

A compensation result generation method based on a binary image and a spray head compensation method. The method comprises: for an area where a macroscopic color difference exists, generating a color difference image Qt of each color surface according to a color difference value of each pixel in an original image and the corresponding position of the printing result; respectively generating a binary image Pt of each color difference image and a binary image P' of the original image; and performing an addition operation or a subtraction operation on each binary image Pt and the binary image P' to generate a compensation result of each color surface; and obtaining a compensation result for printing the original image on the basis of the compensation result of each color surface.

Description

Nozzle Compensation Method Based on Binary Image

technical field

The invention relates to the technical field of printing, in particular to a nozzle compensation method based on a binary image.

Background technique

Inkjet printing refers to a printing method in which ink is attached to a substrate from a nozzle through a computer to obtain graphics and text. It is a printing without contact, pressure, and printing plate. The information stored in the electronic computer can be printed by entering the inkjet printer. An inkjet printing machine is composed of a system controller, an inkjet controller, a nozzle, and a substrate driving mechanism. Under the control of the inkjet controller, the ink is ejected from the nozzles of the print head and printed on the substrate.

In recent years, many printing equipment manufacturers have applied the new technologies of ordinary color inkjet printers to large-format inkjet printers, such as tiny ink droplets, split ink cartridges, color layering and multi-color inks, and micro piezoelectric technology. At the same time, large-format color inkjet printers are favored by users in various industries for their fast, flexible and exquisite output, which has effectively promoted the development of inkjet printing technology and inkjet printing machines.

Compared with traditional large-scale printing equipment, inkjet printing equipment is lower in cost, more convenient to use and maintain, and can win future production capacity through a small investment. It is undoubtedly a powerful weapon for the production of high value-added products. At the same time, the application of a large number of inkjet printing equipment in packaging printing also provides favorable conditions for the standardized production of packaging printed matter. With the continuous development and maturity of the domestic digital printing market, inkjet printing will have greater development.

The main processing flow of inkjet printing, as shown in Figure 1, is first to process files or images, such as parsing PDF files, and the second step is to perform RIP processing on the parsed files, mainly for color management and halftone processing , and then get the processed binary image, which is generally a TIFF format file, and finally, under the control of the printing control equipment, use the nozzle to present the equipment on paper, fabrics and other substrates.

In the printing process, due to the influence of control technology, mechanical process, pressure, etc., there are certain defects in the final printing effect between each nozzle or inside the nozzle, such as a certain area with obvious color difference from other areas, which is called for the ribbon. The existence of these defects greatly affects the final printing effect. By adjusting the original image and optimizing the halftone algorithm, the impact of these defects can be alleviated to a certain extent. However, these methods all have the problems of complex algorithms and poor applicability.

Contents of the invention

In order to solve the above problems, the present invention proposes a compensation result generation method based on a binary image and a nozzle compensation method, and the compensation result is obtained based on the binary image of the color difference map, thereby improving the effect quality of inkjet printing.

The nozzle compensation method based on the binary image of the present invention, its steps include:

The nozzle prints based on the original image and obtains the first print result;

Obtaining all areas in the first printing result where macroscopic color difference exists, and recording all color difference values of each area;

Generate a color difference map of each color surface according to the color difference value of each corresponding pixel in the original image and the region;

Generate the binary image of the color difference map and the binary image corresponding to the original image, adjust each pixel that cannot compensate for the error in the binary image of the color difference map, and obtain the compensation results of each color surface;

After compensating the nozzle according to the above compensation results, continue printing in combination with the original image, and perform the above adjustments on all areas with macroscopic color difference in the printing result until the color difference in the macroscopic color difference area is eliminated.

When the difference between the color difference value of the macroscopic color difference region and the color difference value of the non-macroscopic color difference region in the printing result is smaller than the set threshold, it can be considered that the color difference of the macroscopic color difference region has been eliminated.

Compared with the prior art, the present invention has the following advantages:

1. It only needs one more accurate regional color difference test to get the regional color difference value, which can be applied to all images.

2. Only the binary value to be printed is processed, and there is no need to modify the original image and the halftone algorithm, so the applicability is good.

Description of drawings

FIG. 1 is a flowchart of a conventional inkjet printing method.

Fig. 2 is a flow chart of the chromatic aberration compensation of the nozzle of the present invention.

Fig. 3 is a flow chart of binary image processing in the present invention.

Detailed ways

Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in this specification. It should be understood, however, that in developing any such practical embodiment, many implementation-specific decisions must be made in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and those Restrictions may vary from implementation to implementation.

The main process of the present invention, as shown in Figure 2, includes: first, print a special test chart, the second step is to use a measuring instrument to measure all areas with macroscopic color difference, and record all color difference values in each area, and the third step The first step is to adjust the binary image data in the color difference area in a targeted manner, and finally print the test image again. This process needs to be carried out several times. When the technician thinks that the printing effect is good, or the measurement values of all areas with macroscopic color difference are close to the same as the measurement values of other normal areas (that is, within a set threshold), it can be considered that the accurate color difference is obtained Graph, so as to achieve the best processing effect.

Specifically, the steps of the present invention include:

The nozzle first prints based on the original image, and obtains the print result L ₁ ;

Obtain all areas in _L1 where macroscopic chromatic aberration exists, and record all chromatic aberration values of each area;

For the region where there is macroscopic color difference in the printing result _Lj , according to the color difference value of each pixel in the original image and the corresponding position of the printing result, a color difference map Q _t for each color plane is generated, where t is the color plane number;

Generate the binary image P _t of the color difference map Q _t and the binary image P' of the original image respectively;

The detailed processing flow of the binary image is shown in Figure 3. The first part is to obtain the binary image of the color difference map. First, the test image area to be processed is determined according to the nozzle area, and the actual printing value of each pixel in the current area is calculated according to the measured value. The difference of the gray value of the corresponding position; then use the halftone algorithm, or the frequency modulation algorithm such as error diffusion or dithering, to perform halftone processing on the calculated color difference map to obtain the binary map of the color difference map. The second part is to use the binary image of the color difference map to process all the binary images to be printed.

Specifically, for the binary image P _t , obtain a pixel in the binary image P _t

value, and determine that the pixel

Can the value of can make up for the error; where, i is the pixel serial number;

if pixel

The value of can make up for the error, then return to the binary image P _t to obtain a pixel in the binary image P _t

value, and then process the pixel

if pixel

The value of can not make up the error, then judge whether the corresponding position in the binary image P' can not make up the error;

If the corresponding position in the binary image P' cannot make up for the error, then set the corresponding position to be able to make up for the error, and return to the target binary image P _t to obtain a pixel in the binary image P _t

value, and then process the pixel

If the corresponding position in the binary image P' can make up for the error, then judge the pixel

Whether there are pixels that cannot compensate for the error among the surrounding 8 pixels;

If the pixel

If there is no pixel that can compensate for the error in the surrounding 8 pixels, then return to the binary image P _t to obtain a pixel in the binary image P _t

value, and then process the pixel

If the pixel

If there is a pixel that can make up for the error in the surrounding 8 pixels, set any element to be able to make up for the error, and return to the binary image P _t to obtain a pixel in the binary image P _t

value, and then process the pixel

That is, the binary image of the original image and the binary image of the color difference map are added or subtracted in the corresponding area. The specific process is: process each pixel of the binary image of the color difference map sequentially, if the current pixel is 255 (that is, the error can be compensated), then process the next pixel, otherwise, judge whether the corresponding position in the binary image of the original image is 0, If it is, set it to 255, if not, judge whether there are 0 pixels in the 8 pixels around the pixel, if there is only 1, set this pixel to 255, if there are more than 2, then randomly Choose one of them and set it to 255, if not, just skip and process the next pixel.

When all pixels are processed

After that, obtain the compensation result of the tth color surface;

Obtain the compensation result T _j based on the compensation results of all color surfaces;

Then calculate the compensation result T _j of the printing result L _j , use the compensation result T _j to compensate the nozzle, and then print in combination with the original image to obtain the printing result L _j+1 , where j≥1.

It is easy to understand that if you want to compensate the macroscopic error of the color image, you need to repeat the above process for each color plane.

After multiple compensations, the color difference map of the nozzle color difference area can be accurately obtained, and finally the color difference in the macro color difference area is eliminated, and the optimal compensation result is obtained.

Use the following steps to judge whether the chromatic aberration is eliminated:

1) Based on the original image and the printing result L ₁ , obtain the area with macroscopic color difference and the area without macroscopic color difference;

2) Measure the color difference value C ₁ of the macroscopic color difference area in the printed result _Lj ;

3) Measuring the color difference value _C2 of the macroscopic color difference area that does not exist in the printed result _Lj ;

4) When the difference between the color difference value _C1 and the color difference value _C2 is smaller than a set threshold, it is determined that the color difference has been eliminated.

Compensate the nozzle according to the above optimal compensation result to obtain ideal printing effect.

The method of the present invention does not process the original image, let alone modify and optimize the halftone method, which determines that the method has good applicability.

The above description is only one of the embodiments of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims

A nozzle compensation method based on a binary image, the steps comprising:

The nozzle prints based on the original image and obtains the first print result;

Obtaining all areas in the first printing result where macroscopic color difference exists, and recording all color difference values of each area;

Generate a color difference map of each color surface according to the color difference value of each corresponding pixel in the original image and the region;

Generating the binary image of the color difference map and the binary image corresponding to the original image, and compensating each pixel of the binary image of the color difference map that cannot make up the error to obtain the compensation results of each color surface;

After compensating the nozzle according to the above compensation results, continue printing in combination with the original image, and perform the compensation on all regions with macroscopic color difference in the printing result until the color difference in the macroscopic color difference region is eliminated.
The method according to claim 1, wherein the supplementary results of each color surface are obtained by the following steps: for the area of macroscopic color difference in the print result L j , obtain a pixel in the binary image P t of the color difference map Q t
value, and determine that the pixel
Whether the value of can make up for the error; among them, j≥1 means the number of printing times, t≥1 means the number of the color surface, and i is the number of the pixel;

if pixel
The value of can make up for the error, then return to the binary image P t to obtain a pixel in the binary image P t
value to get the pixel

if pixel
The value of can not make up the error, then judge whether the corresponding position in the binary image P ' of the original picture can not make up the error;

If the corresponding position in the binary image P' cannot make up for the error, then set the corresponding position to be able to make up for the error, and return to the target binary image P t to obtain a pixel in the binary image P t
value to get the pixel

If the corresponding position in the binary image P' can make up for the error, then judge the pixel
Whether there are pixels that cannot compensate for the error among the surrounding 8 pixels;

If the pixel
If there is no pixel that can compensate for the error in the surrounding 8 pixels, then return to the binary image P t to obtain a pixel in the binary image P t
value to get the pixel

If the pixel
If there is a pixel that can make up for the error in the surrounding 8 pixels, set any element to be able to make up for the error, and return to the binary image P t to obtain a pixel in the binary image P t
value to get the pixel

When all pixels are processed
After that, the compensation result of the tth color surface is obtained.
The method according to claim 1, characterized in that, when the difference between the color difference value of the macroscopic color difference region and the color difference value of the macroscopic color difference region in the printing result is less than the set threshold value, the value of the macroscopic color difference region Chromatic aberration is eliminated.
The method according to claim 1, wherein the method for generating the binary image of the color difference map or the binary image of the original image comprises: an error diffusion algorithm or a dithering frequency modulation algorithm.
A storage medium, wherein a computer program is stored in the storage medium, wherein the computer program is configured to perform the method of any one of claims 1-4 when running.
An electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and the processor is configured to run the computer program to perform the method according to any one of claims 1-4.