CN114801487B - Method and system for eliminating printing image saw teeth - Google Patents

Abstract

The invention discloses a method and system for eliminating jagged printing image, the method includes: S1, calculate the size of each pixel according to the resolution of the print head, and calculate the size of the adjacent ink in each group of ink droplets printed on the paper The height difference between drops; S2, calculate the coordinate compensation value corresponding to each ink point according to the size of each pixel and the height difference between adjacent ink drops in each group of ink drops printed on paper; S3, in the raster When transforming, subtract the corresponding coordinate compensation value from the sampling coordinates, and round to get the ink dot coordinates. The method and system for eliminating jagged printing images in the present invention fully consider the offset characteristics of ink droplets in the printing process, first calculate the coordinate compensation value of each ink dot, and subtract the corresponding coordinate compensation value from the sampling coordinates during rasterization, And round to get the ink dot coordinates. After rasterization, multiple pixels in each group are arranged in a downward slanting manner, fully considering the physical position of ink droplets, so that the printed image can obtain better quality.

Description

A method and system for eliminating aliasing in printed images

technical field

The invention relates to the technical field of digital inkjet printing, in particular to a method and system for eliminating jagged print images.

Background technique

There are two mainstream technologies for print heads used in digital inkjet printing, thermal foaming and piezoelectric technology. The thermal foaming technology is to heat the nozzle to make the ink generate bubbles and spray it on the printing medium, which belongs to the high temperature and high pressure printing technology. Its working principle is: use thin-film resistors to instantly heat ink less than 5 picoliters to above 300°C in the ink ejection area to form countless tiny bubbles, which gather into large bubbles at an extremely fast speed of less than 10 microseconds and form Expand, forcing the ink droplet out of the nozzle. Piezoelectric inkjet printing technology belongs to normal temperature and pressure printing technology. It is to place many tiny piezoelectric ceramics near the nozzle of the print head. Piezoelectric ceramics have the characteristics of bending deformation under the action of voltage changes at both ends. When applied to piezoelectric ceramics, the stretching vibration deformation of piezoelectric ceramics will change with the change of image information voltage, and the ink in the nozzle can be ejected evenly and accurately under the stable state of normal temperature and pressure.

Thermal foam printing often has the advantages of many nozzles, small ink droplets, and high precision. At the same time, due to the large number of nozzles, it is impossible to spray all at once, and the injection of all the nozzle holes needs to be sprayed multiple times to complete a full spray. Moreover, due to the movement of the printing medium relative to the nozzle during the printing process, the ink droplets on the paper will tend to slope downward, as shown in FIG. 1 .

Figure 1 is a simulation of the printing process of a domestic thermal foaming print head. The print head has 30,720 nozzles, which need to be divided into 32 batches to complete a full spray, and each batch sprays 960 nozzles. Due to the movement of the paper, there will be an 8-micron offset between two adjacent ink droplets in the horizontal direction, so that a horizontal straight line will become many small slanted lines that slope downward, which will affect the printing process. Image quality.

Since there is a maximum downward offset of 8*7=56 microns in the horizontal direction, which exceeds the diameter of an ink droplet of 21 microns, it is possible to simply move the position of some pixels with severe deviation to the position of the previous line, this A simple processing method can have a large improvement, as shown in Figure 2.

The defect in Figure 1 is that the pixels on the printed image have a serious downward shift. After simple optimization, it can be seen from Figure 2 that the effect of the downward shift is relatively better, but there is a certain degree of upward and downward shift. Offset, up to a maximum of 18 microns, down to a maximum of 14 microns.

Although the simple optimization method from Figure 1 to Figure 2 has been greatly improved, considering that 18 microns and 14 microns are relatively large values relative to the ink droplet diameter of 21 microns, the simple optimization method shown in Figure 2 It doesn't completely solve the problem. A more complete method is urgently needed to optimize the .

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for eliminating aliasing of printed images, which fully considers the offset characteristics of ink droplets during printing and considers the physical position of ink droplets during rasterization.

In order to solve the above problems, the present invention provides a method for eliminating jagged printing images, and the method for eliminating jagged printing images includes the following steps:

S1. Calculate the size of each pixel according to the resolution of the print head, and calculate the height difference between adjacent ink drops in each group of ink drops printed on the paper; wherein, the print head includes several printing units, each printing The nozzles in the unit are distributed on m columns, each column has n nozzles, and the m columns of ink droplets printed on the paper are divided into n groups, and the m columns of ink droplets in the same group are printed sequentially in time sequence; m≥ 2; n≥1;

S2. Calculate the coordinate compensation value corresponding to each ink dot according to the size of each pixel and the height difference between adjacent ink droplets in each group of ink droplets printed on the paper;

S3. During rasterization, the corresponding coordinate compensation value is subtracted from the sampling coordinates, and rounded to obtain the ink dot coordinates.

As a further improvement of the present invention, the size of each pixel calculated according to the resolution of the print head is:

Among them, a*b is the resolution of the print head, that is, there are a ink dots per inch in the horizontal direction, and b ink dots per inch in the vertical direction; A and B are the resolution of each pixel in the horizontal direction and vertical direction, respectively. size;

And use the following formula to calculate the height difference S _interval between adjacent ink droplets in each group of ink droplets printed on the paper:

S _interval ＝V×T _interval

Among them, V is the relative movement speed between the print head and the paper, and T _interval is the interval printing time between adjacent ink droplets in each group of ink droplets.

As a further improvement of the present invention, the coordinate compensation value y corresponding to each ink dot is _compensated as:

y _compensation = (x%m) × (-S _interval /B)

Wherein, y _compensation is the compensation in the vertical direction, x%m is the remainder of x to m, and x is the xth ink drop in time sequence in each group of ink drops.

As a further improvement of the present invention, the ink dot coordinates obtained by rounding in step S3 are:

表示对x向上取整，

表示对x使用四舍五入的方式取整。Wherein, (x _sample , y _sample ) is the sampling coordinate; ( _xi , y _i ) is the ink dot coordinate obtained;

Indicates that x is rounded up,

Indicates that x is rounded to an integer.

The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and operable on the processor, and the processor implements the steps of any one of the methods described above when executing the program .

The present invention also provides a computer-readable storage medium, on which a computer program is stored, which is characterized in that, when the program is executed by a processor, the steps of any one of the above-mentioned methods are implemented.

The present invention also provides a system for eliminating jagged printing images, which includes:

The first calculation module is used to calculate the size of each pixel according to the resolution of the print head, and calculate the height difference between adjacent ink drops in each group of ink drops printed on the paper; wherein the print head includes several print heads unit, the nozzles in each printing unit are distributed on m columns, each column has n nozzles, and the m columns of ink droplets printed on the paper are grouped into n groups, and the m columns of ink droplets in the same group are in the timing Print sequentially; m≥2; n≥1;

The second calculation module is used to calculate the coordinate compensation value corresponding to each ink point according to the size of each pixel and the height difference between adjacent ink droplets in each group of ink droplets printed on the paper;

The compensation module is used for subtracting the corresponding coordinate compensation value from the sampling coordinates during rasterization, and rounding to obtain the ink dot coordinates.

As a further improvement of the present invention, the size of each pixel calculated according to the resolution of the print head is:

Among them, a*b is the resolution of the print head, that is, there are a ink dots per inch in the horizontal direction, and b ink dots per inch in the vertical direction; A and B are the resolution of each pixel in the horizontal direction and vertical direction, respectively. size;

And use the following formula to calculate the height difference S _interval between adjacent ink droplets in each group of ink droplets printed on the paper:

S _interval ＝V×T _interval

Among them, V is the relative movement speed between the print head and the paper, and T _interval is the interval printing time between adjacent ink droplets in each group of ink droplets.

As a further improvement of the present invention, the coordinate compensation value y corresponding to each ink dot is _compensated as:

y _compensation = (x%m) × (-S _interval /B)

Wherein, y _compensation is the compensation in the vertical direction, x%m is the remainder of x to m, and x is the xth ink drop in time sequence in each group of ink drops.

As a further improvement of the present invention, the ink dot coordinates obtained by rounding are:

表示对x向上取整，

表示对x使用四舍五入的方式取整。Wherein, (x _sample , y _sample ) is the sampling coordinate; ( _xi , y _i ) is the ink dot coordinate obtained;

Indicates that x is rounded up,

Indicates that x is rounded to an integer.

Beneficial effects of the present invention:

The method and system for eliminating jagged printing images in the present invention fully consider the offset characteristics of ink droplets in the printing process, first calculate the coordinate compensation value of each ink dot, and subtract the corresponding coordinate compensation value from the sampling coordinates during rasterization, And round to get the ink dot coordinates. After rasterization, multiple pixels in each group are arranged in a downward slanting manner, fully considering the physical position of ink droplets, so that the printed image can obtain better quality.

The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable , the following preferred embodiments are specifically cited below, and are described in detail as follows in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is the simulation of the printing process of the existing thermal foaming print head;

Fig. 2 is the simulation of the printing process after the optimization of the existing thermal foaming print head;

FIG. 3 is a schematic diagram of existing linear rasterization;

Fig. 4 is a schematic diagram of linear rasterization considering the printing process in the present invention;

Fig. 5 is a schematic diagram of the nozzles of the print head in the embodiment of the present invention;

Fig. 6 is a schematic diagram of ink dots of a printed image in an embodiment of the present invention;

Fig. 7 is a schematic diagram of a line segment path in an embodiment of the present invention;

Fig. 8 is a schematic diagram of a line segment with sampling points in an embodiment of the present invention;

Fig. 9 is a schematic diagram of a straight line in an embodiment of the present invention;

Fig. 10 is a schematic diagram of a straight line sampling the x-axis in an embodiment of the present invention;

Fig. 11 is a schematic diagram of linear rasterization in an embodiment of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

Embodiment one

A preferred embodiment of the present invention discloses a method for eliminating jagged print images, including the following steps:

S1. Calculate the size of each pixel according to the resolution of the print head, and calculate the height difference between adjacent ink drops in each group of ink drops printed on the paper; wherein, the print head includes several printing units, each printing The nozzles in the unit are distributed on m columns, each column has n nozzles, and the m columns of ink droplets printed on the paper are divided into n groups, and the m columns of ink droplets in the same group are printed sequentially in time sequence; m≥ 2; n≥1.

Specifically, the size of each pixel calculated according to the resolution of the print head is:

Among them, a*b is the resolution of the print head, that is, there are a ink dots per inch in the horizontal direction, and b ink dots per inch in the vertical direction; A and B are the resolution of each pixel in the horizontal direction and vertical direction, respectively. size.

And use the following formula to calculate the height difference S _interval between adjacent ink droplets in each group of ink droplets printed on the paper:

S _interval ＝V×T _interval

Among them, V is the relative movement speed between the print head and the paper, and T _interval is the interval printing time between adjacent ink droplets in each group of ink droplets.

In one of the embodiments, taking a certain print head as an example, the resolution of the print head is 1200×600, that is, there are 1200 ink dots per inch in the horizontal direction, and 600 ink dots per inch in the vertical direction. Ink dots, it can be calculated that the size of each pixel printed on paper is 21.167μm×42.333μm, the calculation process is as follows:

1inch＝2.54cm＝0.0254m

0.0254m÷1200＝21.167μm

0.0254m÷600＝42.333μm

The print head is composed of several units, each unit has 32 nozzles, distributed in 8 columns, each column has 4 nozzles, the horizontal width is: 21.167μm×8=169.336μm, the vertical height is: 42.333μm× 32=1354.656 μm, the nozzle distribution diagram of the print head is shown in FIG. 5 .

For each inkjet of the print head is called a latch, the 32 nozzles of each unit need 32 latch cycles to spray, and only one nozzle works in each latch cycle, and the 32 latches are latch 1 to latch32.

The ink droplets printed on the paper are divided into groups of 8 columns, and there are n groups in total, and the 8 columns in the same group are printed sequentially in time sequence.

With V=1.0m/s, T _interval =8μs, it can be calculated:

S _interval = V × T _interval = 1.0 m/s × 8 μs = 8 μm.

S2. Calculate the coordinate compensation value corresponding to each ink dot according to the size of each pixel and the height difference between adjacent ink droplets in each group of ink droplets printed on the paper.

Specifically, the coordinate compensation value y _compensation corresponding to each ink point is:

y _compensation = (x%m) × (-S _interval /B)

Wherein, y _compensation is the compensation in the vertical direction, x%m is the remainder of x to m, and x is the xth ink drop in time sequence in each group of ink drops.

In one embodiment, a schematic diagram of ink dots of a printed image is shown in FIG. 6 . x ₀ means x=0; x ₁ means x=1; and so on. Use (x, y) to represent the coordinates of the ink dot, but (x, y) cannot directly correspond to the actual position of the ink dot, and y needs to be compensated. Vertically:

1 ink dot = 42.333μm

and:

If you want to obtain the actual position of the ink point (x, y), you need to compensate y. When x=0, you need to compensate 0 for y; when x=1, you need to compensate -0.189 for y; when x=2, you need to compensate y compensation -0.378; ...; when x=9, it is necessary to compensate 0 for y; and so on.

Record y _compensation as y compensation, then y _compensation satisfies the following formula:

y _compensation = (x%8) × -0.189

The actual position of the ink point (x, y) is: (x, y+y _compensation ).

S3. During rasterization, the corresponding coordinate compensation value is subtracted from the sampling coordinates, and rounded to obtain the ink dot coordinates.

Specifically, the ink dot coordinates obtained by rounding are:

表示对x向上取整，

表示对x使用四舍五入的方式取整。Wherein, (x _sample , y _sample ) is the sampling coordinate; ( _xi , y _i ) is the ink dot coordinate obtained;

Indicates that x is rounded up,

Indicates that x is rounded to an integer.

Take drawing a straight line as an example to illustrate the rasterization process. The pixel position of the straight line path can be determined according to the geometric features of the straight line. The Cartesian slope-intercept equation of a line is:

y=m x+b

Among them, m is the slope of the line, and b is the ending of the y-axis. Given the two endpoints (x ₀ , y ₀ ) and (x _end , y _end ) of the line segment shown in Figure 7, the slope m and the intercept of y can be calculated as b:

b=y ₀ -m x ₀

For any given x-increment δx along the line, the corresponding y-increment can be calculated as δy:

δy=m·δx

Likewise, the x-increment δx corresponding to the specified δy can be obtained:

For a straight line with an absolute value of |m|<1, a smaller δx can be set, and the corresponding δy can be calculated; for a straight line with a slope value of |m|>1, a smaller δy can be set, and the corresponding δx It can be calculated; for a straight line with slope m=1, δx=δy, both δx and δy can be set.

In a raster system, lines are drawn by pixels, and the horizontal and vertical steps are limited by the pitch of the pixels. That is, the line segment must be sampled at discrete locations, and the nearest pixel to the line segment must be determined at each sampled location. As shown in Figure 8, the scan conversion process of the line segment and the discrete sampling point positions relative to the x-axis are given.

The specific steps of rasterization are as follows:

As shown in FIG. 9, the equation of the straight line is y=mx+b.

(1) Determine the sampling direction

|m|<1, sample the x axis; |m|>1 sample the y; |m|=1 sample both x and y.

(2) Sampling

Samples on the x-axis or y-axis according to the given start (x ₀ , y ₀ ) and end (x _end , y _end ). Take sampling in the x direction as an example, assuming x ₀ =0, x _end =10.5, x ₀ and x _end contain 11 sampling points, which are x=0, x=1,...,x=10, remember these 11 The sampling points are x _sample0 , x _sample1 , ... x _sample10 , as shown in FIG. 10 .

(3) Calculate coordinates

The coordinates of the corresponding sampling points are calculated according to the formula y=mx+b of the straight line. For example, 11 sampling points sampled on the x-axis in 2) can calculate 11 y values, namely y _sample0 , y _sample1 , ... y _sample10 , then the coordinates of the 11 sampling points are (x _sample0 , y _sample0 ) ,(x _sample1 ,y _sample1 ),...,(x _sample10 ,y _sample10 ).

(4) Adjust the sampling coordinates to the ink dot coordinates

In (3), the sampling coordinates calculated according to the straight line equation are subtracted from the compensation in the y direction, and the coordinates ( _xi , y _i ) of the ink point are obtained by rounding, where:

表示对x向上取整，

表示对x使用四舍五入的方式取整。图11为直线y＝mx+b的光栅化结果。in,

Indicates that x is rounded up,

Indicates that x is rounded to an integer. Fig. 11 is the rasterization result of the straight line y=mx+b.

As shown in FIG. 3 , it is a process of rasterizing a straight line under normal circumstances, in which pixels are arranged in horizontal and vertical directions.

As shown in Figure 4, it is the rasterization process that considers the characteristic that ink droplets will slope downward during the printing process in the present invention. In this process, the pixels are no longer distributed according to a strict horizontal and vertical grid, but there are 8 The pixels are arranged in a downward sloping manner in groups. The physical position of the ink drop is taken into account during the rasterization process, so that the printed image can achieve better quality.

Embodiment two

This embodiment discloses an electronic device, including a memory, a processor, and a computer program stored on the memory and operable on the processor. When the processor executes the program, the steps of the methods described in the above embodiments are implemented. .

Embodiment three

This embodiment discloses a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the methods described in the above-mentioned embodiments are implemented.

Embodiment Four

This embodiment discloses a system for eliminating jagged printing images, which includes:

The first calculation module is used to calculate the size of each pixel according to the resolution of the print head, and calculate the height difference between adjacent ink drops in each group of ink drops printed on the paper; wherein the print head includes several print heads unit, the nozzles in each printing unit are distributed on m columns, each column has n nozzles, and the m columns of ink droplets printed on the paper are grouped into n groups, and the m columns of ink droplets in the same group are in the timing Print sequentially; m≥2; n≥1;

The second calculation module is used to calculate the coordinate compensation value corresponding to each ink point according to the size of each pixel and the height difference between adjacent ink droplets in each group of ink droplets printed on the paper;

The compensation module is used for subtracting the corresponding coordinate compensation value from the sampling coordinates during rasterization, and rounding to obtain the ink dot coordinates.

Specifically, the size of each pixel calculated according to the resolution of the print head is:

Among them, a*b is the resolution of the print head, that is, there are a ink dots per inch in the horizontal direction, and b ink dots per inch in the vertical direction; A and B are the resolution of each pixel in the horizontal direction and vertical direction, respectively. size;

And use the following formula to calculate the height difference S _interval between adjacent ink droplets in each group of ink droplets printed on the paper:

S _interval ＝V×T _interval

Among them, V is the relative movement speed between the print head and the paper, and T _interval is the interval printing time between adjacent ink droplets in each group of ink droplets.

Specifically, the coordinate compensation value y _compensation corresponding to each ink point is:

y _compensation = (x%m) × (-S _interval /B)

Wherein, y _compensation is the compensation in the vertical direction, x%m is the remainder of x to m, and x is the xth ink drop in time sequence in each group of ink drops.

Specifically, the ink dot coordinates obtained by rounding are:

表示对x向上取整，

表示对x使用四舍五入的方式取整。Wherein, (x _sample , y _sample ) is the sampling coordinate; ( _xi , y _i ) is the ink dot coordinate obtained;

Indicates that x is rounded up,

Indicates that x is rounded to an integer.

The system for eliminating aliasing of a printed image in the embodiment of the present invention is used to implement the aforementioned method for eliminating aliasing of a printed image, so the specific implementation of the system can be seen in the embodiment part of the method for eliminating aliasing of a printed image above, so its specific For the implementation manner, reference may be made to the description of the corresponding method embodiments above, and no further introduction is made here.

In addition, since the system for eliminating aliasing in a printed image of this embodiment is used to implement the aforementioned method for eliminating aliasing in a printed image, its function corresponds to that of the above method, and will not be repeated here.

The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be determined by the claims.

Claims (6)

1. A method for eliminating jagged printing images, characterized in that, comprising the following steps: S1. Calculate the size of each pixel according to the resolution of the print head, and calculate the height difference between adjacent ink drops in each group of ink drops printed on the paper; wherein, the print head includes several printing units, each printing The nozzles in the unit are distributed on m columns, each column has n nozzles, and the m columns of ink droplets printed on the paper are divided into n groups, and the m columns of ink droplets in the same group are printed sequentially in time sequence; m≥ 2; n≥1; S2. Calculate the coordinate compensation value corresponding to each ink dot according to the size of each pixel and the height difference between adjacent ink droplets in each group of ink droplets printed on the paper; S3. During rasterization, subtract the corresponding coordinate compensation value from the sampling coordinates, and round to obtain the ink dot coordinates; The size of each pixel calculated according to the resolution of the print head is:

Meter

Meter Among them, a*b is the resolution of the print head, that is, there are a ink dots per inch in the horizontal direction, and b ink dots per inch in the vertical direction; A and B are the resolution of each pixel in the horizontal direction and vertical direction, respectively. size; And use the following formula to calculate the height difference S _interval between adjacent ink droplets in each group of ink droplets printed on the paper: S _interval ＝V×T _interval Among them, V is the relative motion speed of the print head and the paper, and T _interval is the interval printing time between adjacent ink droplets in each group of ink droplets; The coordinate compensation value y _compensation corresponding to each ink point is: y _compensation = (x%m) × (-S _interval /B) Wherein, y _compensation is the compensation in the vertical direction, x%m is the remainder of x to m, and x is the xth ink drop in time sequence in each group of ink drops. 2. The method for eliminating jagged print image as claimed in claim 1, wherein the ink dot coordinates obtained by rounding up in step S3 are:

Wherein, (x _sample , y _sample ) is the sampling coordinate; ( _xi , y _i ) is the ink dot coordinate obtained;

Indicates that x is rounded up,

Indicates that x is rounded to an integer. 3. An electronic device comprising a memory, a processor, and a computer program stored on the memory and operable on the processor, wherein the processor implements any of claims 1-2 when executing the computer program. A step of said method. 4. A computer-readable storage medium, on which a computer program is stored, characterized in that, when the program is executed by a processor, the steps of the method according to any one of claims 1-2 are implemented. 5. A system for eliminating jagged printing images, characterized in that it comprises: The first calculation module is used to calculate the size of each pixel according to the resolution of the print head, and calculate the height difference between adjacent ink drops in each group of ink drops printed on the paper; wherein the print head includes several print heads unit, the nozzles in each printing unit are distributed on m columns, each column has n nozzles, and the m columns of ink droplets printed on the paper are grouped into n groups, and the m columns of ink droplets in the same group are in the timing Print sequentially; m≥2; n≥1; The second calculation module is used to calculate the coordinate compensation value corresponding to each ink point according to the size of each pixel and the height difference between adjacent ink droplets in each group of ink droplets printed on the paper; The compensation module is used for subtracting the corresponding coordinate compensation value from the sampling coordinates during rasterization, and rounding to obtain the ink dot coordinates; The size of each pixel calculated according to the resolution of the print head is:

Meter

Meter Among them, a*b is the resolution of the print head, that is, there are a ink dots per inch in the horizontal direction, and b ink dots per inch in the vertical direction; A and B are the resolution of each pixel in the horizontal direction and vertical direction, respectively. size; And use the following formula to calculate the height difference S _interval between adjacent ink droplets in each group of ink droplets printed on the paper: S _interval ＝V×T _interval Among them, V is the relative motion speed of the print head and the paper, and T _interval is the interval printing time between adjacent ink droplets in each group of ink droplets; The coordinate compensation value y _compensation corresponding to each ink point is: y _compensation = (x%m) × (-S _interval /B) Wherein, y _compensation is the compensation in the vertical direction, x%m is the remainder of x to m, and x is the xth ink drop in time sequence in each group of ink drops. 6. The system for eliminating jagged print images as claimed in claim 5, wherein the ink dot coordinates obtained by rounding are:

Wherein, (x _sample , y _sample ) is the sampling coordinate; ( _xi , y _i ) is the ink dot coordinate obtained;

Indicates that x is rounded up,

Indicates that x is rounded to an integer.

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