Overprinting method

Abstract

The invention discloses an overprinting method which is used for overprinting a second pattern on a printing medium with a first pattern. The overprinting method includes a process of forming at least one reference region, deforming all the reference regions to form a deformed region, and re-deforming the deformed region to form a pattern to be printed, and a process of printing the pattern to be printed onto a printing medium. By adopting the technical scheme, compared with the prior art, a better overprinting effect can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of digital printing, in particular to a superimposition method. BACKGROUND

[0002] In the prior art, a pattern can be printed on a printing medium, which is generally a fabric, by digital inkjet printing technology. A special digital inkjet printing is to superimpose a second pattern on a printing medium already having a first pattern. However, since the printing medium as a fabric is soft and easily deformed, the second pattern needs to be deformed accordingly so as to obtain a better effect when superimposing the second pattern on the actual first pattern.

[0003] In the prior art, the existing superimposition method includes finding a plurality of feature positions on an actual image of a printing medium by image recognition technology, finding corresponding feature positions on a theoretical image of a first pattern based on the feature positions on the actual image of the printing medium, obtaining grid information after comparison, and printing a deformed second pattern on the first pattern based on the above grid information. After printing by using the above technical solution, the superimposition effect is still poor.

[0004] In the prior art, there are digital inkjet printing machines and printing methods that stepwise perform digital inkjet printing to print a pattern on a printing medium that is continuous along a stepping direction. The above superimposition method can also be stepwise performed in the prior art, but the superimposition effect is still poor. SUMMARY

[0005] The present application aims to overcome the above-mentioned defects or problems in the background art, and to provide a superimposition method that can obtain a better superimposition effect compared to the prior art.

[0006] To achieve the above-mentioned purpose, the following technical solutions are adopted.

[0007] The first technical solution relates to an overprinting method for overprinting a second pattern on a printing medium with a first pattern; the overprinting method comprises a process of forming a to-be-printed pattern corresponding to the first pattern on the printing medium and a process of printing the to-be-printed pattern to the printing medium; the process of forming the to-be-printed pattern corresponding to the first pattern on the printing medium comprises: step S1: acquiring an image of the printing medium to form an actual image; step S2: determining a plurality of feature point pairs on the actual image and a reference image, so that all reference feature points form a reference region of a polygon or at least two reference regions of polygons that are continuous with each other and do not overlap on the reference image; step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to coincide with corresponding actual feature points; step S4: judging whether there are feature sub-point pairs, if not, forming a deformed universe from all deformed regions and performing step S6, if yes, dividing each deformed region of the existing deformed feature sub-point into a deformed sub-region of a polygon based on the deformed feature sub-point and performing step S5; step S5: deforming all deformed sub-regions, so that all deformed feature sub-points are deformed to coincide with corresponding actual feature sub-points, and after each deformed sub-region after deformation is marked as a new deformed region, returning to step S4 or forming a deformed universe from all deformed regions and performing step S6; step S6: deforming the second pattern based on the deformation rule from the reference universe to the deformed universe to form the to-be-printed pattern; wherein the reference image is a theoretical image of the first pattern; the feature point pair comprises an actual feature point located on the actual image and a corresponding reference feature point located on the reference image; the feature sub-point pair comprises a deformed feature sub-point located in the deformed region and a corresponding actual feature sub-point located on the actual image, whose distance exceeds a threshold; and the reference universe is formed by all reference regions.

[0008] The second technical solution is based on the first technical solution, wherein the reference region is a quadrilateral, and the deformed sub-region is a triangle.

[0009] The third technical solution is based on the first technical solution, wherein in step S2, when determining the feature point pair, one of the actual image and the reference image is a semi-transparent image and is overlaid on the other; and in step S4, when judging whether there are feature sub-point pairs, one of the deformed universe and the actual image is a semi-transparent image and is overlaid on the other.

[0010] The fourth technical solution is based on the first technical solution, wherein in step S2, the feature point pairs are determined one by one.

[0011] The fifth technical solution is based on the first technical solution, wherein in step S2, when determining the feature point pair, the reference universe also covers a theoretical to-be-taken region; wherein the theoretical to-be-taken region refers to a region in the theoretical image of the first pattern corresponding to a part that needs to be used after printing is completed.

[0012] The sixth technical solution is based on the first technical solution, wherein in step S2, when determining the feature point pairs, first, a plurality of feature point pairs are selected, and if a reference universe formed by the selected feature point pairs does not cover the theoretical region to be taken, at least part of the feature point pairs are moved so that the reference universe covers the theoretical region to be taken.

[0013] The seventh technical solution is based on the first technical solution, wherein step S6 includes deforming a reference peripheral image based on a deformation rule from the reference universe to the deformed universe to form a deformed peripheral image, and deforming a second pattern based on a deformation rule from the reference image to the deformed image to form a to-be-printed pattern; wherein the reference peripheral image is a part of the reference image not covered by the reference universe; and the deformed image is formed by the deformed universe and the deformed peripheral image.

[0014] The eighth technical solution relates to an overprinting method for overprinting a second pattern on a printing medium with a first pattern; the overprinting method comprises the processes of stepwise forming a to-be-printed pattern corresponding to a to-be-printed part of the printing medium and stepwise printing the to-be-printed pattern to the to-be-printed part; each process of stepwise forming a to-be-printed pattern corresponding to a to-be-printed part of the printing medium comprises: step S1: acquiring an image of the to-be-printed part of the printing medium to form an actual image; step S2: determining a plurality of feature point pairs on the actual image and the reference image, so that all reference feature points form a reference region of a polygon on the reference image or at least two reference regions of polygons that are continuous with each other and do not overlap; step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to coincide with corresponding actual feature points; step S4: judging whether there are feature sub-point pairs, if not, forming a deformed universe from all deformed regions and performing step S6, if yes, dividing each deformed region of the existing deformed feature sub-point into a deformed sub-region of a polygon based on the deformed feature sub-point and performing step S5; step S5: deforming all deformed sub-regions, so that all deformed feature sub-points are deformed to coincide with corresponding actual feature sub-points, and after each deformed sub-region after deformation is marked as a new deformed region, returning to step S4 or forming a deformed universe from all deformed regions and performing step S6; step S6: deforming the reference peripheral image to form a deformed peripheral image based on the deformation rule of the reference universe to the deformed universe, and deforming the step second image to form the to-be-printed pattern based on the deformation rule of the reference image to the deformed image; wherein the reference image of the first step is the step theoretical first image of the first step, the step theoretical first image of each step is all or a part including the part corresponding to the actual image of the current step of the theoretical image of the first pattern; the reference image of each step except the first step is the image formed by deforming the step theoretical first image of the current step based on the deformation rule of the step theoretical first image of the last step to the deformed image of the last step; the step second image of the first step is the step theoretical second image of the first step, the step theoretical second image of each step is the part corresponding to the step theoretical first image of the current step in the theoretical image of the second pattern; the step second image of each step except the first step is the image formed by deforming the step theoretical second image of the current step based on the deformation rule of the step theoretical first image of the last step to the deformed image of the last step; each step feature point pair includes an actual feature point located on the actual image of the current step and a corresponding reference feature point located on the reference image of the current step; each step feature sub-point pair includes a deformed feature sub-point located in the deformed region of the current step and a corresponding actual feature sub-point located on the actual image of the current step, the distance between which exceeds a threshold; the reference universe of each step is formed by all reference regions of the current step.The reference peripheral image of each step is a part of the reference image of the current step which is not covered by the reference domain of the current step; and the deformed image of each step is formed by the deformed domain of the current step and the deformed peripheral image of the current step.

[0015] The ninth technical solution is based on the eighth technical solution, wherein the reference region is a quadrilateral, and the deformed sub-region is a triangle.

[0016] The tenth technical solution is based on the eighth technical solution, wherein in step S2, when determining the feature point pair, one of the actual image and the reference image is a semi-transparent image and is overlaid on the other; and in step S4, when determining whether the feature sub-point pair exists, one of the deformed domain and the actual image is a semi-transparent image and is overlaid on the other.

[0017] The eleventh technical solution is based on the eighth technical solution, wherein in step S2, the feature point pairs are determined one by one.

[0018] The twelfth technical solution is based on the eighth technical solution, wherein after each step of forming the to-be-printed pattern, the to-be-printed pattern is printed to the corresponding to-be-printed part at least once.

[0019] The thirteenth technical solution relates to an overprinting method for overprinting a second pattern on a printing medium with a first pattern; the overprinting method comprises the processes of stepwise forming a to-be-printed pattern corresponding to a to-be-printed part of the printing medium of the last step and stepwise printing the to-be-printed pattern to the corresponding to-be-printed part; each step after the first step comprises the following steps: step S1: obtaining an actual image of the to-be-printed part of the printing medium of the current step; step S2: determining a plurality of feature point pairs on the actual image and a reference image, so that the deformed feature points of the last step and the reference feature points of the current step jointly form a reference region of a polygon or at least two reference regions of polygons that are continuous with each other and do not overlap; step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to deformed feature points that coincide with the corresponding actual feature points; step S4: determining whether there are feature sub-point pairs, if not, forming a deformed universe from all deformed regions and performing step S6, if yes, dividing each deformed region with a deformed feature sub-point into a deformed sub-region of a polygon based on the deformed feature sub-point and performing step S5; step S5: deforming all deformed sub-regions, so that all deformed feature sub-points are deformed to coincide with the corresponding actual feature sub-points, and after each deformed sub-region is marked as a new deformed region after deformation, returning to step S4 or forming a deformed universe from all deformed regions and performing step S6; step S6: deforming a step second region of the current step based on a deformation rule from a reference universe to a deformed universe to form a local image of the current step, or deforming a step theoretical second region of the current step based on a deformation rule from a theoretical universe to a deformed universe to form a local image of the current step; and forming a to-be-printed pattern corresponding to the to-be-printed part of the last step based on the local image of the current step and the local image of the last step; in the first step, the remaining steps are the same as the corresponding steps of each subsequent step, except for steps S2 and S6; step S2 of the first step: determining a plurality of feature point pairs on the actual image and a step theoretical first image of the first step, so that all reference feature points form a reference region of a polygon or at least two reference regions of polygons that are continuous with each other and do not overlap; step S6 of the first step: deforming a step theoretical second region to form a local image of the first step based on a deformation rule from a theoretical universe to a deformed universe; wherein the reference image is an image formed by deforming a step theoretical first image of the current step based on a deformation rule from a theoretical universe of the last step to a deformed universe of the last step, the step theoretical first image of each step is all or a part of a local theoretical image of the first pattern that includes a part corresponding to the actual image of the current step, the theoretical universe of each step is the largest region enclosed by the theoretical feature points on the step theoretical first image of the current step, and the theoretical feature points of each step are the points on the step theoretical first image of the current step corresponding to the reference feature points of the current step; the reference universe of each step is jointly formed by the reference regions of the current step.The feature point pair of each step includes an actual feature point located on the actual image of the current step and a reference feature point correspondingly located on the reference image of the current step; the feature sub-point pair of each step includes a deformed feature sub-point located in the deformed region of the current step and an actual feature sub-point correspondingly located on the actual image of the current step, and the distance between the deformed feature sub-point and the actual feature sub-point exceeds a threshold; the step second region of each step is a region formed by deforming the step theoretical second region of the current step based on the deformed global region of the last step to the deformed global region of the last step according to the deformation rule, the step theoretical second region of each step is a region corresponding to the theoretical global region of the current step in the step theoretical second image of the current step, and the step theoretical second image of each step is a part corresponding to the step theoretical first image of the current step in the theoretical image of the second pattern.

[0020] The fourteenth technical solution is based on the thirteenth technical solution, wherein in step S2 of the first step, when determining the feature point pair, one of the actual image and the step theoretical first image is a semi-transparent image and is overlaid on the other; in step S2 of each step except the first step, when determining the feature point pair, one of the actual image and the reference image is a semi-transparent image and is overlaid on the other; and in step S4, when determining whether the feature sub-point pair exists, one of the deformed global region and the actual image is a semi-transparent image and is overlaid on the other.

[0021] The fifteenth technical solution is based on the thirteenth technical solution, wherein in step S2 of each step, the feature point pairs are determined one by one.

[0022] The sixteenth technical solution is based on the thirteenth technical solution, wherein in step S2 of each step except the first step, when determining the feature point pair, the number of the reference feature points is the same as the number of the adjacent deformed feature points, each reference feature point is distributed along the width direction perpendicular to the step direction, and the deformed feature points of the last step used to form the reference region are all the adjacent deformed feature points of the last step; and the adjacent deformed feature points of each step are part or all of the deformed feature points of the last step close to the step theoretical first image of the current step along the step direction.

[0023] The seventeenth technical solution is based on the sixteenth technical solution, wherein the reference region is a quadrilateral, and the deformed sub-region is a triangle.

[0024] The eighteenth technical solution is based on the seventeenth technical solution, wherein in step S2 of the first step, when determining the feature point pair, the first condition that both sides of the theoretical region to be taken have at least two reference feature points distributed along the stepping direction should be met; in step S2 of each step except the first step, when determining the feature point pair, the second condition that both sides of the region to be taken have at least one reference feature point should be met; wherein the theoretical region to be taken of each step is the region corresponding to the part to be used after printing in the theoretical first image of the current step, and the region to be taken of each step is the region formed by deforming the theoretical region to be taken of the current step based on the theoretical whole region of the last step to the deformed whole region of the last step.

[0025] The nineteenth technical solution is based on the eighteenth technical solution, wherein in step S2 of the first step, when determining the feature point pair, the feature point pair is first selected, and if the selected feature point pair does not meet the first condition, at least part of the feature point pair is moved until the first condition is met; in step S2 of each step except the first step, when determining the feature point pair, the feature point pair is first selected, and if the selected feature point pair does not meet the second condition, at least part of the feature point pair is moved until the second condition is met.

[0026] Compared with the prior art, the above-mentioned solutions have the following beneficial effects: After continuous experiments, analysis and research, the applicant determined that because the fabric as the printing medium is soft and easy to deform, the printing medium not only has overall deformation with large scale, but also has local deformation with small scale, such as wrinkles, concave-convex, etc., and the deformation parameters of the local deformation with small scale are often quite different from the deformation parameters of the overall deformation with large scale. Therefore, the prior art solution cannot eliminate the poor overprint effect caused by the local deformation with small scale.

[0027] In the first, eighth and thirteenth technical solutions, by steps S4 and S5, after completing the first deformation, the local deformation with large difference between the deformation parameters and the overall deformation can be further deformed and corrected, so that a better overprint effect can be obtained compared with the prior art. Compared with the solution of selecting more feature point pairs in the first deformation, the solution removes the influence of the local deformation with small difference between the deformation parameters and the overall deformation on the efficiency, so that higher printing efficiency can be achieved. The above steps can be performed cyclically or only once. Cyclically performing the first deformation sub-process is beneficial to further improve the overprint effect, and performing the first deformation sub-process only once is beneficial to ensure high printing efficiency.

[0028] In the first, eighth and thirteenth technical solutions, whether there is a feature sub-point pair is determined after the first deformation, which is more efficient and less likely to make mistakes than determining the feature point pair at the first deformation. Otherwise, if the feature point pair used to represent local displacement is selected before the first deformation, it is often far apart in the overall scale, which is prone to errors.

[0029] Compared with the use of a grid to achieve deformation in the prior art, in the first, eighth and thirteenth technical solutions, step 2 uses the reference area formed by each reference feature point to deform, which has a larger scale and better integrity.

[0030] In the second, ninth and seventeenth technical solutions, the reference area is a quadrilateral, which is more easily deformed once using two-dimensional affine transformation or a local deformation function (such as bilinear interpolation, bicubic interpolation, etc.), and is suitable for large-scale overall deformation of the printing medium. The deformation sub-area is a triangle, which is more easily used to control the nonlinear deformation of the local area by the vertices of the triangle.

[0031] In the third, tenth and fourteenth technical solutions, in step S2, one of the actual image and the reference image is a semi-transparent image and is overlaid on the other; in step S4, one of the deformation universe and the actual image is a semi-transparent image and is overlaid on the other, which enables people to more intuitively observe and select the feature point pair and the distance-exceeding feature sub-point pair.

[0032] The fourth, eleventh and fifteenth technical solutions are important improvements of the present application compared with the prior art. The prior art first selects all the actual feature points in the actual image, and then selects the reference feature points on the reference image based on the actual feature points. This method makes the selection extremely inefficient, and it is often difficult to determine the correspondence between the actual feature points and the reference feature points. Selecting the feature point pair and the feature sub-point pair one by one enables people to directly select the actual feature points and the reference feature points with no doubt about the correspondence, and to give up the correspondence between the actual feature points and the reference feature points which are difficult to determine, and to make the judgment easier and less likely to make mistakes by judging whether there is a feature sub-point pair after the first deformation.

[0033] In the sixth, seventh, eighteenth and nineteenth technical solutions, the reference universe can cover the to-be-taken area or span the to-be-taken area in the width direction, so there is no longer a need to deform the reference peripheral image, and therefore the deformation is simpler and more efficient.

[0034] In step S6 of the seventh and eighth technical solutions, the deformation rule of deforming the reference universe to the deformation universe is applied to the deformed reference peripheral image, which makes the superposition effect better and is more capable of meeting the situation where the to-be-taken area is close to the edge of the pattern, or all the patterns are within the to-be-taken area.

[0035] In the eighth technical solution and the thirteenth technical solution, the reference image of each step except the first step is an image formed by deforming the step theoretical first image of the current step based on the deformed image of the last step according to the deforming rule, or is an image formed by deforming the step theoretical first image of the current step based on the deformed whole domain of the last step according to the deforming rule. Thus, the reference image is deformed according to the deforming rule of the last step, so that when the feature point pair is selected at each step, the actual feature point and the reference feature point are relatively close, thereby facilitating the selection or determination of the feature point pair, and reducing the error rate of determining the feature point pair.

[0036] Compared with the eighth technical solution, the thirteenth technical solution can avoid the problem that after the corresponding to-be-printed patterns of two adjacent to-be-printed parts are printed, the pattern misalignment occurs between the two parts, so that the continuity of the pattern superimposed along the stepping direction is better. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments, the following briefly introduces the drawings needed to be used: Figure 1 is a theoretical image of the first pattern in the embodiment one; Figure 2 is a second pattern in the embodiment one; Figure 3 is a superimposition effect expected to be achieved in the embodiment one; Figure 4 is an actual image obtained in step S1 in the embodiment one; Figure 5 is a schematic diagram of step S2 in the embodiment one; Figure 1 ; Figure 6 is a schematic diagram of step S2 in the embodiment one; Figure 2 ; Figure 7 is a schematic diagram of step S2 in the embodiment one; Figure 3 ; Figure 8 is a schematic diagram of step S3 in the embodiment one; Figure 9 is a schematic diagram of step S4 in the embodiment one; Figure 10 is a schematic diagram of step S5 in the embodiment one; Figure 11 is a superimposition effect after step S6 is completed in the embodiment one; Figure 12 is a theoretical image of the first pattern in the embodiment three and the embodiment four; Figure 13 is a theoretical image of the second pattern in the embodiment three and the embodiment four; Figure 14 The superimposed effect achieved for each step in Example Three and Example Four; Figure 15 The actual image acquired for step S1 for each step in Example Three and step S1 for the first step in Example Three; Figure 16 The schematic for step S2 for each step in Example Three Figure 1 ; Figure 17 The schematic for step S2 for each step in Example Three Figure 2 ; Figure 18 The schematic for step S3 for each step in Example Three; Figure 19 The schematic for step S4 for each step in Example Three; Figure 20 The schematic for step S5 for each step in Example Three Figure 1 ; Figure 21 The schematic for step S6 for each step in Example Three Figure 1 ; Figure 22 The superimposed effect achieved after step S6 for each step in Example Three; Figure 23 The schematic for step S2 for the first step in Example Four Figure 1 ; Figure 24 The schematic for step S2 for the first step in Example Four Figure 2 ; Figure 25 The schematic for step S3 for the first step in Example Four; Figure 26 The schematic for step S4 for the first step in Example Four; Figure 27 The schematic for step S5 for the first step in Example Four; Figure 28 The actual image acquired for step S1 for each step in Example Four except the first step; Figure 29 The schematic for step S2 for each step in Example Four except the first step Figure 1 ; Figure 30 The schematic for step S2 for each step in Example Four except the first step Figure 2 ; Figure 31 The schematic for step S3 for each step in Example Four except the first step; Figure 32The overprint effect after step S6 is completed for each step except the first step in Example 4. DETAILED DESCRIPTION

[0038] In the claims and specification, the terms "first", "second", or "third" and the like, unless otherwise specified, are used for distinguishing between similar objects and are not necessarily used to describe a particular sequential or chronological order.

[0039] In the claims and specification, the terms "fixedly connected", "fixedly connected" or "relatively fixed", unless otherwise specified, should be understood in a broad sense, that is, any connection mode between the two without displacement relationship and relative rotation relationship, that is, including non-detachable fixed connection, detachable fixed connection, integration and fixed connection through other devices or elements.

[0040] In the claims and specification, the terms "including", "having" and their variants, unless otherwise specified, mean "including but not limited to".

[0041] In the claims and specification, the term "provided with", unless otherwise specified, means that the technical feature located after it is part of the technical feature located before it.

[0042] Example 1 The overprint method in this embodiment is used to overprint a second pattern on a printing medium with a first pattern. Referring to Figure 1 、 Figure 2 and Figure 3 , Figure 1 shows the theoretical image of the first pattern in this embodiment. Figure 2 shows the second pattern in this embodiment. Figure 3 shows the overprint effect expected to be achieved after overprinting the second pattern on the first pattern in this embodiment. The printing medium in this embodiment is fabric. Because fabric is soft and easy to deform, stretching, wrinkling, concave-convex deformation and the like are prone to occur before and during printing. Therefore, the second pattern needs to be deformed to correspond to the first pattern on the real printing medium, so as to obtain a better overprint effect.

[0043] The overprint method includes a process of forming a to-be-printed pattern corresponding to the first pattern on the printing medium and a process of printing the to-be-printed pattern to the printing medium. In this embodiment, the second pattern needs to be deformed as a whole before being overprinted on the second pattern.

[0044] In this embodiment, the process of forming a to-be-printed pattern corresponding to the first pattern on the printing medium includes: Step S1: obtaining an image of the printing medium to form an actual image; The actual image of the print medium is acquired from a camera. The camera is arranged above the print medium to capture the whole first pattern of the print medium. Of course, when the first pattern of the print medium is large in size, the actual image of the first pattern of the print medium can be captured in parts and then synthesized into a whole actual image. The actual image in the embodiment is shown in Figure 4 .

[0045] Step S2: determining a plurality of feature point pairs on the actual image and the reference image, so that all the reference feature points form a reference region of a polygon or at least two reference regions of polygons which are continuous with each other and do not overlap on the reference image. The reference pattern is a theoretical image of the first pattern. The feature point pairs include an actual feature point on the actual image and a corresponding reference feature point on the reference image.

[0046] As shown in Figure 5 , one of the reference image and the actual image is processed into a semi-transparent image by running a computer program and overlaid on the other. In the embodiment, the reference image is processed into a semi-transparent image and overlaid on the actual image. In other embodiments, the actual image can be processed into a semi-transparent image and overlaid on the reference image. A plurality of feature point pairs on the actual image and the reference image can be determined by running a computer program or manually selected, so that all the reference feature points form a reference region of a polygon or at least two reference regions of polygons which are continuous with each other and do not overlap on the reference image. In the embodiment, the feature point pairs are selected one by one by an operator, i.e. an actual feature point and a reference feature point form a feature point pair, and then the next feature point pair is selected. In the embodiment, an actual feature point A1 on the actual image and a reference feature point B1 on the reference image are selected to form a feature point pair AB1, and then an actual feature point A2 on the actual image and a reference feature point B2 on the reference image are selected to form a feature point pair AB2, an actual feature point A3 on the actual image and a reference feature point B3 on the reference image are selected to form a feature point pair AB3, an actual feature point A4 on the actual image and a reference feature point B4 on the reference image are selected to form a feature point pair AB4, an actual feature point A5 on the actual image and a reference feature point B5 on the reference image are selected to form a feature point pair AB5, and finally an actual feature point A6 on the actual image and a reference feature point B6 on the reference image are selected to form a feature point pair AB6. After the feature point pairs are selected by the operator, it is determined by running a computer program whether the reference domain (shown by the dotted line frame in Figure 5 ) formed by all the reference feature points covers the actual region (shown by the solid line frame in Figure 5The dashed box in FIG. 6 illustrates the reference polygonal region formed by the selected reference feature points. The reference polygonal region refers to the largest polygonal region that can be enclosed by all the selected reference feature points. The theoretical area to be taken refers to the area in the theoretical image of the first pattern that corresponds to the area that needs to be taken after printing. If the reference polygonal region formed by all the selected reference feature points does not cover the theoretical area to be taken, at least some of the reference feature points are moved so that the reference polygonal region covers the theoretical area to be taken. As shown in FIG. 6, the reference polygonal region formed by the selected reference feature points does not cover the theoretical area to be taken. Therefore, the reference feature point pair AB5 is moved downward, and a new reference feature point pair AB5 is formed so that the reference polygonal region formed by all the selected reference feature points covers the theoretical area to be taken. Figure 5 and Figure 6 As shown in FIG. 6, the reference polygonal region formed by the selected reference feature points does not cover the theoretical area to be taken. Therefore, the reference feature point pair AB5 is moved downward, and a new reference feature point pair AB5 is formed so that the reference polygonal region formed by all the selected reference feature points covers the theoretical area to be taken. Figure 7 As shown in FIG. 6, the reference polygonal region formed by the selected reference feature points does not cover the theoretical area to be taken. Therefore, the reference feature point pair AB5 is moved downward, and a new reference feature point pair AB5 is formed so that the reference polygonal region formed by all the selected reference feature points covers the theoretical area to be taken.

[0047] Step S3: Deforming all the reference regions to form deformed regions so that all the reference feature points are deformed to coincide with the corresponding actual feature points. As shown in FIG. 6, the reference polygonal region formed by the selected reference feature points does not cover the theoretical area to be taken. Therefore, the reference feature point pair AB5 is moved downward, and a new reference feature point pair AB5 is formed so that the reference polygonal region formed by all the selected reference feature points covers the theoretical area to be taken. Figure 8 As shown in FIG. 6, the reference polygonal region formed by the selected reference feature points does not cover the theoretical area to be taken. Therefore, the reference feature point pair AB5 is moved downward, and a new reference feature point pair AB5 is formed so that the reference polygonal region formed by all the selected reference feature points covers the theoretical area to be taken.

[0048] Step S4: Determining whether there are feature sub-points. If there are no feature sub-points, a deformed global region is formed by all the deformed regions, and step S6 is performed. If there are feature sub-points, each deformed region in which a feature sub-point exists is divided into polygonal deformed sub-regions based on the feature sub-point, and step S5 is performed. The feature sub-point pair includes a deformed feature sub-point in a deformed region and a corresponding actual feature sub-point on the actual image, which are apart from each other by more than a threshold distance.

[0049] When step S4 is performed, the deformed region E1 and the deformed region E2 are processed as a semi-transparent image by running a computer program, and one of the two is overlaid on the other. In this embodiment, the deformed region is processed as a semi-transparent image, and is overlaid on the actual image. In other embodiments, the actual image can also be processed as a semi-transparent image, and is overlaid on the deformed region. Whether a feature point pair exists can be determined by running a computer program or by an operator. As shown in Figure 9 In this embodiment, a feature point pair exists in the deformed region E1, and the feature point pair includes the actual feature point A7 on the actual image and the deformed feature point F7 on the deformed region E1. The deformed region E1 in which the deformed feature point F7 exists is divided into polygonal deformed sub-regions based on the deformed feature point F7. In this embodiment, the deformed sub-regions are triangles. Therefore, the deformed region E1 is divided into the deformed sub-region G1, the deformed sub-region G2, the deformed sub-region G3, and the deformed sub-region G4 by the deformed feature point F7.

[0050] Step S5: After deforming all the deformed sub-regions so that all the deformed feature points are deformed to coincide with the corresponding actual feature points, and each deformed sub-region after deformation is labeled as a new deformed region, return to step S4 or form a deformed universe from all the deformed regions and perform step S6. Step S5 is performed by running a computer program. As shown in Figure 10 In this embodiment, the deformed sub-region G1 is deformed into a new deformed region E3, the deformed sub-region G2 is deformed into a new deformed region E4, the deformed sub-region G3 is deformed into a new deformed region E5, and the deformed sub-region G4 is deformed into a new deformed region E6, so that the deformed feature point F7 is deformed to the deformed feature point D7 corresponding to the actual feature point A7. The deformed universe E is formed from the deformed region E2, the deformed region E3, the deformed region E4, the deformed region E5, and the deformed region E6. After deformation is completed, step S6 can be continued to be performed, or return to step S4. In this embodiment, step S4 is continued to be performed, but no feature point pair can be found, so it is switched to perform step S6.

[0051] Step S6: Deform the second pattern based on the deformation rule from the reference universe to the deformed universe to form a to-be-printed pattern.

[0052] Step S6 is performed by running a computer program. In this embodiment, the second pattern is deformed based on the deformation rule from the reference universe C to the deformed universe E to form a printed pattern.

[0053] After the to-be-printed pattern is printed on the printing medium, the formed pattern and the overprint effect are as shown in Figure 11

[0054] Embodiment Two ​The difference between the second embodiment and the first embodiment is that the step S6 includes deforming the reference peripheral image based on the deformation rule from the reference universe to the deformed universe to form a deformed peripheral image, and deforming the second pattern based on the deformation rule from the reference image to the deformed image to form the to-be-printed pattern. The reference peripheral image is the part of the reference image not covered by the reference universe C; the deformed image is formed by the deformed universe E and the deformed peripheral image. The method of deforming the reference peripheral image to form the deformed peripheral image can be to divide the reference peripheral image into a plurality of reference peripheral sub-images adjacent to the edges of the reference universe C, each reference peripheral sub-image is deformed according to the deformation rule of the edge of the reference universe C adjacent to it, and then the image formed by all the deformed reference peripheral sub-images is combined to form the deformed peripheral image.

[0055] The second embodiment can be used in a situation where the theoretical to-be-taken region cannot be selected or a situation where the theoretical to-be-taken region is very close to the edge of the pattern. For example, when all the patterns on the printing medium need to be used, the solution of the second embodiment can be used.

[0056] Embodiment Three The overprinting method in this embodiment is used to overprint a second pattern on a printing medium with a first pattern. Referring to Figure 12 Figure 13 Figure 14 Figure 12 Fig. 6 shows the theoretical image of the first pattern in this embodiment. Figure 13 Fig. 7 shows the second pattern in this embodiment. Figure 14 Fig. 8 shows the overprinting effect expected to be achieved after the second pattern is overprinted on the first pattern in this embodiment. The printing medium in this embodiment is a fabric, which is very long in the length direction, for example, it can be in a roll. Since the fabric is soft and easy to deform, it is easy to stretch, wrinkle, and have concave-convex deformation before and during printing. Therefore, the second pattern needs to be deformed to correspond to the first pattern on the real printing medium, so as to obtain a better overprinting effect.

[0057] The overprinting method of this embodiment includes the process of stepwise forming a to-be-printed pattern corresponding to the to-be-printed part of the printing medium and the process of stepwise printing the to-be-printed pattern to the to-be-printed part. After each step of forming the to-be-printed pattern, at least one step of printing the to-be-printed pattern to the corresponding to-be-printed part is experienced. In this embodiment, after each step of forming the to-be-printed pattern, three steps of printing the to-be-printed pattern to the corresponding to-be-printed part are experienced.

[0058] In this embodiment, the process of stepwise forming a to-be-printed pattern corresponding to the to-be-printed part of the printing medium each time includes: Step S1: obtaining an image of the to-be-printed part of the printing medium to form an actual image; ​​​An actual image of the to-be-printed part of the print medium is acquired from a camera. The camera is located upstream of a print unit of the printer along the stepping direction and is arranged above the to-be-printed part to capture an image containing the to-be-printed part. The actual image in the present embodiment is as shown in Figure 15 .

[0059] Step S2: determining a plurality of feature point pairs on the actual image and the reference image, so that all the reference feature points form a polygonal reference region on the reference image or at least two polygonal reference regions which are continuous with each other and do not overlap. wherein the reference image of the first stepping is the stepping theoretical first image of the first stepping, the stepping theoretical first image of each stepping is all of the theoretical image of the first pattern or a partial including a part corresponding to the actual image of the present stepping; the reference image of each stepping except the first stepping is an image formed by deforming the stepping theoretical first image of the present stepping based on the deforming rule of the deformed image of the stepping theoretical first image of the last stepping to the deformed image of the last stepping. The feature point pairs include an actual feature point on the actual image of the present stepping and a corresponding reference feature point on the reference image of the present stepping.

[0060] As shown in Figure 16 , one of the reference image and the actual image is processed into a semi-transparent image by running a computer program and is overlaid on the other. In the present embodiment, the reference image is processed into a semi-transparent image and is overlaid on the actual image. In other embodiments, the actual image can also be processed into a semi-transparent image and is overlaid on the reference image. A plurality of feature point pairs on the actual image and the reference image can be determined by running a computer program or manually selecting, so that all the reference feature points form a polygonal reference region on the reference image or at least two polygonal reference regions which are continuous with each other and do not overlap. In the present embodiment, the feature point pairs are selected one by one by an operator, i.e. after selecting an actual feature point and a reference feature point to form a feature point pair AB1, the next feature point pair AB2 is selected, and then the feature point pair AB3 is selected, and then the feature point pair AB4 is selected. As shown in Figure 17As shown, all reference feature points collectively form a polygonal reference region C1, and all reference regions collectively form the reference global region C. In this embodiment, reference region C1 is a quadrilateral. In other embodiments, the number of reference regions may be two or more, continuous and non-overlapping, or other polygonal shapes. The portion of the reference image not covered by the reference global region C forms a reference peripheral image I. In this embodiment, reference peripheral image I includes a reference peripheral sub-image I1 located in front of the reference global region C along the stepping direction, and a reference peripheral sub-image I2 located behind the reference global region C along the stepping direction.

[0061] Step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to coincide with corresponding actual feature points; like Figure 18 As shown, reference region C1 is deformed to deformed region E1, so that reference feature point B1 is deformed to deformed feature point D1, which coincides with actual feature point A1; reference feature point B2 is deformed to deformed feature point D2, which coincides with actual feature point A2; reference feature point B3 is deformed to deformed feature point D3, which coincides with actual feature point A3; and reference feature point B4 is deformed to deformed feature point D4, which coincides with actual feature point A4. Deformed region E1 forms the entire deformation domain E.

[0062] Step S4: Determine whether there is a feature sub-point pair. If not, all deformation regions are combined to form a deformation domain and step S6 is executed. If so, each deformation region with a deformation feature sub-point is divided into polygonal deformation sub-regions based on the deformation feature sub-points and step S5 is executed. The feature sub-point pairs include a deformed feature sub-point located in the deformed region and having a distance therebetween exceeding a threshold, and an actual feature sub-point correspondingly located on the actual image.

[0063] When executing step S4, by running a computer program, one of the deformed domain E formed by the deformed area E1 and the actual image is processed into a semi-transparent image and overlaid on the other. In this embodiment, the deformed domain is processed into a semi-transparent image and overlaid on the actual image. In other embodiments, the actual image can also be processed into a semi-transparent image and overlaid on the deformed domain. The existence of a characteristic sub-point pair can be determined by running a computer program or by an operator. Figure 19As shown, in this embodiment, a feature sub-point pair exists within the deformed region E1. The feature sub-point pair includes an actual feature sub-point A5 located on the actual image and a deformed feature sub-point F5 located within the deformed region E1. The deformed region E1, containing the deformed feature sub-point F5, is then divided into polygonal deformed sub-regions based on the deformed feature sub-point F5. In this embodiment, the deformed sub-regions are triangular. Therefore, the deformed region E1 is divided into deformed sub-regions G1, G2, G3, and G4 based on the deformed feature sub-point F5.

[0064] Step S5: deform all deformed sub-regions so that all deformed feature sub-points are deformed to coincide with the corresponding actual feature sub-points, and each deformed sub-region is marked as a new deformed region, and then return to step S4 or form a deformed full domain from all deformed regions and execute step S6; Step S5 is executed by running a computer program. Figure 20 As shown, in this embodiment, deformed sub-region G1 is deformed into a new deformed region E2, which is then deformed into a new deformed region E3, which is then deformed into a new deformed region E4, and which is then deformed into a new deformed region E5, so that the deformed feature sub-point F5 is deformed to the deformed feature point D5 corresponding to the actual feature sub-point A5. Deformed regions E2, E3, E4, and E5 together form the entire deformed domain E. After the deformation is complete, the process can proceed to step S6 or return to step S4. In this embodiment, step S6 is continued.

[0065] Step S6: deforming the reference peripheral image to form a deformed peripheral image based on the deformation rule from the reference full domain to the deformed full domain, and deforming the stepped second image to form a pattern to be printed based on the deformation rule from the reference image to the deformed image; The deformed image is formed by combining the deformed global image and the deformed peripheral image. The first step's second image is the theoretical second image of the first step. The theoretical second image of each step is the portion of the theoretical image of the second pattern that corresponds to the theoretical first image of the current step. The second image of each step other than the first step is the image formed by deforming the theoretical second image of the current step based on the deformation rule from the theoretical first image of the previous step to the deformed image of the previous step.

[0066] Step S6 is performed by running a computer program. Figure 21As shown, the reference peripheral image I is deformed to form the deformed peripheral image J based on the deformation rule from the reference universe C to the deformed universe E, wherein the reference peripheral sub-image I1 is deformed to the deformed peripheral sub-image J1 based on the deformation rule from the edge of the reference universe C to which the reference peripheral sub-image I1 is adjacent, the reference peripheral sub-image I2 is deformed to the deformed peripheral sub-image J2 based on the deformation rule from the edge of the reference universe C to which the reference peripheral sub-image I2 is adjacent, and the deformed peripheral image J is formed by the deformed peripheral sub-image J1 and the deformed peripheral sub-image J2 together, and the deformed image is formed by the deformed universe E and the deformed peripheral image J together, and the to-be-printed pattern is formed based on the deformation rule from the reference image C to the deformed image by deforming the second image step by step.

[0067] After the to-be-printed pattern is formed each time step by step, the to-be-printed pattern is printed to the corresponding to-be-printed part by undergoing three steps. Figure 22 The pattern and the overprint effect formed after the to-be-printed pattern is printed to the to-be-printed part are shown.

[0068] Embodiment Four The overprint method in this embodiment is used to overprint a second pattern on a printing medium with a first pattern. The first pattern, the second pattern and the overprint effect expected to be achieved in this embodiment are the same as those in Embodiment Three, as shown in Figure 12 , Figure 13 and Figure 14 Embodiment Three. The printing medium in this embodiment is also the same as that in Embodiment Three.

[0069] The overprint method in this embodiment includes a process of forming a to-be-printed pattern corresponding to the to-be-printed part of the printing medium in the last step and a process of printing the to-be-printed pattern to the corresponding to-be-printed part step by step. After the to-be-printed pattern corresponding to the to-be-printed part is formed, the to-be-printed pattern can be printed to the corresponding to-be-printed part in this step or can be printed to the to-be-printed part after undergoing at least one step. In this embodiment, after the to-be-printed pattern corresponding to the to-be-printed part is formed, the to-be-printed pattern is printed to the corresponding to-be-printed part in this step.

[0070] In this embodiment, the first step includes the following steps: Step S1: obtaining an image of the to-be-printed part of the printing medium to form an actual image; The actual image of the to-be-printed part of the printing medium is obtained from a camera. The camera is located upstream of the printing unit of the printer along the stepping direction and is arranged above the to-be-printed part to capture an image containing the to-be-printed part. The actual image in this embodiment is shown in Figure 15 .

[0071] Step S2: determining a plurality of feature point pairs on the actual image and the stepping theoretical first image of the first step so that all reference feature points form a reference region of a polygon or at least two reference regions of polygons which are continuous with each other and do not overlap; The theoretical first image of a step is the entire theoretical image of the first pattern, or a portion thereof corresponding to the actual image of the current step. In this embodiment, the theoretical first image of a step encompasses and is larger than the portion corresponding to the actual image of the current step. A feature point pair includes an actual feature point located on the actual image of the current step and a corresponding reference feature point located on the reference image of the current step.

[0072] like Figure 23 As shown, by running a computer program, one of the step-theoretic first image and the actual image is processed into a semi-transparent image and overlaid on the other. In this embodiment, the step-theoretic first image is processed into a semi-transparent image and overlaid on the actual image. In other embodiments, the actual image can also be processed into a semi-transparent image and overlaid on the step-theoretic first image. By running a computer program or manually selecting, several feature point pairs on the actual image and the step-theoretic first image can be determined so that all reference feature points form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping on the reference image. In this embodiment, the operator selects the feature point pairs one by one, that is, after selecting the actual feature point and the reference feature point to form a feature point pair, the next feature point pair is selected. In this embodiment, the actual feature point A1 located on the actual image and the reference feature point B1 located on the reference image are first selected to form a feature point pair AB1, and then the actual feature point A2 on the actual image and the reference feature point B2 located on the reference image are selected to form a feature point pair AB2, the actual feature point A3 on the actual image and the reference feature point B3 located on the reference image are selected to form a feature point pair AB3, and the actual feature point A4 on the actual image and the reference feature point B4 located on the reference image are selected to form a feature point pair AB4. In step S2 of the first step, when determining the feature point pair, the first condition that there are at least two reference feature points distributed along the step direction on both sides of the theoretical area to be taken should be met. The theoretical area to be taken refers to the area in the theoretical first image of this step that corresponds to the part to be used after printing is completed ( Figure 23 The portion between the two dashed lines is the theoretical area to be selected. A computer program can be run to determine whether all feature point pairs satisfy the first condition. If the selected feature point pairs do not satisfy the first condition, at least some of the feature point pairs are moved until the first condition is satisfied. In this embodiment, all selected feature point pairs satisfy the first condition.

[0073] like Figure 24 As shown, all reference feature points together form a polygonal reference area C1, and all reference areas together form the reference full domain C. In this embodiment, the reference area C1 is a quadrilateral. In other embodiments, the number of reference areas may be two or more, continuous and non-overlapping, and the reference areas may also be other polygons.

[0074] Step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to coincide with corresponding actual feature points; like Figure 25 As shown, reference region C1 is deformed to deformed region E1, so that reference feature point B1 is deformed to deformed feature point D1, which coincides with actual feature point A1; reference feature point B2 is deformed to deformed feature point D2, which coincides with actual feature point A2; reference feature point B3 is deformed to deformed feature point D3, which coincides with actual feature point A3; and reference feature point B4 is deformed to deformed feature point D4, which coincides with actual feature point A4. Deformed region E1 forms the entire deformation domain E.

[0075] Step S4: Determine whether there is a feature sub-point pair. If not, all deformation regions are combined to form a deformation domain and step S6 is executed. If so, each deformation region with a deformation feature sub-point is divided into polygonal deformation sub-regions based on the deformation feature sub-points and step S5 is executed. The feature sub-point pairs include a deformed feature sub-point located in the deformed region and having a distance therebetween exceeding a threshold, and an actual feature sub-point correspondingly located on the actual image.

[0076] When executing step S4, by running a computer program, one of the deformed domain E formed by the deformed area E1 and the actual image is processed into a semi-transparent image and overlaid on the other. In this embodiment, the deformed domain is processed into a semi-transparent image and overlaid on the actual image. In other embodiments, the actual image can also be processed into a semi-transparent image and overlaid on the deformed domain. The existence of a characteristic sub-point pair can be determined by running a computer program or by an operator. Figure 26 As shown, in this embodiment, a feature sub-point pair exists within the deformed region E1. The feature sub-point pair includes an actual feature sub-point A5 located on the actual image and a deformed feature sub-point F5 located within the deformed region E1. The deformed region E1, containing the deformed feature sub-point F5, is then divided into polygonal deformed sub-regions based on the deformed feature sub-point F5. In this embodiment, the deformed sub-regions are triangular. Therefore, the deformed region E1 is divided into deformed sub-regions G1, G2, G3, and G4 based on the deformed feature sub-point F5.

[0077] Step S5: deform all deformed sub-regions so that all deformed feature sub-points are deformed to coincide with the corresponding actual feature sub-points, and each deformed sub-region is marked as a new deformed region, and then return to step S4 or form a deformed full domain from all deformed regions and execute step S6; Step S5 is executed by running a computer program. Figure 27As shown, in this embodiment, the deformed sub-region G1 is deformed into a new deformed region E2, the deformed sub-region G2 is deformed into a new deformed region E3, the deformed sub-region G3 is deformed into a new deformed region E4, and the deformed sub-region G4 is deformed into a new deformed region E5, so that the deformed feature sub-point F5 is deformed to the deformed feature point D5 corresponding to the actual feature sub-point A5. The deformed region E2, the deformed region E3, the deformed region E4, and the deformed region E5 together form a deformed whole region E. After deformation, step S6 can be continued or returned to step S4. In this embodiment, step S6 is continued.

[0078] Step S6: deforming a step theory second region based on a deformation rule from a theory whole region to a deformed whole region to form a first stepped local image; wherein the theory whole region is a largest region enclosed by theory feature points on a step theory first image of this step, the theory feature points are points on the step theory first image of this step corresponding to reference feature points of this step; the step theory second region is a region in a step theory second image of this step corresponding to the theory whole region of this step, the step theory second image is a part of a theory image of a second pattern corresponding to the step theory first image of this step.

[0079] Step S6 is executed by running a computer program.

[0080] In this embodiment, each step except the first step includes the following steps: Step S1: obtaining an image of a to-be-printed part of a printing medium to form an actual image; Figure 28 An actual image of the second step of this embodiment is shown.

[0081] Step S2: determining a plurality of feature point pairs on the actual image and a reference image, so that the deformed feature points of the last step and the reference feature points of this step together form a reference region of a polygon or at least two reference regions of polygons which are continuous and do not overlap with each other; wherein the reference image is an image formed by deforming a step theory first image of this step based on a deformation rule from a theory whole region of the last step to a deformed whole region of the last step.

[0082] As Figure 29As shown, by running a computer program, one of the reference image and the actual image is processed into a semi-transparent image and overlaid on the other. In this embodiment, the reference image is processed into a semi-transparent image and overlaid on the actual image. In other embodiments, the actual image can also be processed into a semi-transparent image and overlaid on the reference image. By running a computer program or manually selecting, a number of feature point pairs on the actual image and the reference image can be determined so that all reference feature points form a polygonal reference area or at least two continuous and non-overlapping polygonal reference areas on the reference image. In this embodiment, the feature point pairs are selected one by one by an operator. That is, after selecting the actual feature points and the reference feature points to form a feature point pair, the next feature point pair is selected.

[0083] like Figure 29 As shown, in each step except the first step, when determining the feature point pairs, the number of reference feature points is made equal to the number of adjacent deformed feature points, and each reference feature point is distributed along the width direction perpendicular to the step direction, and the deformed feature points of the previous step used to form the reference area are all the adjacent deformed feature points of the previous step. Among them, the adjacent deformed feature points are part or all of the first theoretical image of the step close to the current step along the step direction among all the deformed feature points of the previous step. In this embodiment, Figure 29 As shown, the adjacent deformation feature points are the deformation feature point D3 and the deformation feature point D4 of the last step, and the number of adjacent deformation feature points is two.

[0084] like Figure 29 As shown, in this embodiment, the actual feature point A6 located on the left side of the actual image and the reference feature point B6 located on the reference image are first selected to form a feature point pair AB6, and then the actual feature point A7 on the right side of the actual image and the reference feature point B7 located on the reference image are selected to form a feature point pair AB7. In step S2 of each step except the first step, when determining the feature point pair, the second condition that there is at least one reference feature point on both sides of the area to be taken should be met. Among them, the area to be taken is the area formed after the theoretical area to be taken of this step is deformed based on the deformation rule from the theoretical full domain of the previous step to the deformation full domain of the previous step. It is possible to determine whether all feature point pairs meet the second condition by running a computer program. If the selected feature point pairs do not meet the second condition, at least part of the feature point pairs are moved until the second condition is met. In this embodiment, all selected feature point pairs meet the second condition.

[0085] like Figure 30As shown, all adjacent deformation feature points and all reference feature points together form a polygonal reference region C3. All reference regions C3 together form the reference global region C. In this embodiment, the reference region C3 is a quadrilateral. In other embodiments, the number of reference regions may be two or more, continuous and non-overlapping, or other polygonal shapes.

[0086] Step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to coincide with corresponding actual feature points; like Figure 31 As shown, the reference area C3 is deformed to the deformation area E6, so that the reference feature point B6 is deformed to the deformation feature point D6 that coincides with the actual feature point A6, and the reference feature point B7 is deformed to the deformation feature point D7 that coincides with the actual feature point A7. The deformation area E1 forms the deformation domain E.

[0087] Step S4: Determine whether there is a feature sub-point pair. If not, all deformation regions are combined to form a deformation domain and step S6 is executed. If so, each deformation region with a deformation feature sub-point is divided into polygonal deformation sub-regions based on the deformation feature sub-points and step S5 is executed. Step S5: deform all deformed sub-regions so that all deformed feature sub-points are deformed to coincide with the corresponding actual feature sub-points, and each deformed sub-region is marked as a new deformed region, and then return to step S4 or form a deformed full domain from all deformed regions and execute step S6; In each step except the first step, step S4 and step S5 are the same as those in the first step and are not described in detail here.

[0088] Step S6: deforming the second stepping area of ​​the current stepping based on the deformation rule from the reference full domain to the deformed full domain to form a partial image of the current stepping, or deforming the theoretical second stepping area of ​​the current stepping based on the deformation rule from the theoretical full domain to the deformed full domain to form a partial image of the current stepping; and forming a to-be-printed pattern corresponding to the to-be-printed portion of the previous stepping based on the partial image of the current stepping and the partial image of the previous stepping; The second region of the step is a region formed after the theoretical second region of the current step is deformed based on the deformation rule from the theoretical full domain of the previous step to the deformation full domain of the previous step.

[0089] Specifically, the pattern to be printed corresponding to the portion to be printed in the first step formed by the second step is printed to the corresponding portion to be printed in the second step. Figure 32 shown.

[0090] In the above three embodiments, after one deformation is completed, the local deformation with a large difference between the deformation parameters and the overall deformation can be continuously deformed and corrected in steps S4 and S5, so that a better superimposition effect can be obtained compared with the prior art. Compared with the scheme of selecting more feature point pairs during one deformation, the influence of the local deformation with a small difference between the deformation parameters and the overall deformation on the efficiency is removed, so that higher printing efficiency can be achieved. The above steps can be performed cyclically or only once. Cyclically performing the first deformation sub-process is beneficial to further improve the superimposition effect, and performing the first deformation sub-process only once is beneficial to ensure high printing efficiency.

[0091] In the above four embodiments, whether there is a feature sub-point pair is determined after the first deformation, which is more efficient and less prone to errors compared with determining the feature point pair during the first deformation. Otherwise, if the feature point pair used to represent the local displacement is selected before the first deformation, it is often far apart in the overall scale and prone to errors.

[0092] Compared with the use of a grid to achieve deformation in the prior art, in the above four embodiments, step 2 uses the reference area formed by the reference feature points to deform, which has a larger scale and better integrity.

[0093] In the above four embodiments, the reference area is a quadrilateral, which is more easily deformed once using two-dimensional affine transformation or a local deformation function (such as bilinear interpolation, bicubic interpolation, etc.), and is suitable for the overall deformation of a large-scale printing medium. The deformation sub-area is a triangle, which is more easily used to control the nonlinear deformation of the local area by the vertices of the triangle.

[0094] In the above four embodiments, in step S2, when determining the feature point pair, one of the actual image and the reference image is a semi-transparent image and is overlaid on the other; in step S4, when judging whether there is a feature sub-point pair, one of the deformation universe and the actual image is a semi-transparent image and is overlaid on the other; which can make people more intuitively observe and select the feature point pair and the distance-exceeding feature sub-point pair.

[0095] In the above four embodiments, the feature point pairs and the feature sub-point pairs are selected one by one, which allows people to directly select the actual feature points and the reference feature points with no doubt about the corresponding relationship, and gives up the corresponding relationship between the actual feature points and the reference feature points which are difficult to determine. By judging whether there is a feature sub-point pair after one deformation, the judgment is easier and less prone to errors.

[0096] In embodiments one and four, the reference full area can cover the to-be-taken area or span the to-be-taken area along the width direction, so there is no need to deform the peripheral image of the reference, and therefore the deformation is simpler and more efficient.

[0097] In the embodiment two and the embodiment three, the superimposition effect is better, and the situation that the to-be-taken region is closer to the pattern edge or all the patterns are in the to-be-taken region can be better met by applying the deformation rule of deforming the reference full domain to the deformed full domain to the deformed reference peripheral image.

[0098] In the embodiment three and the embodiment four, the reference image of each step except the first step is an image formed by deforming the step theoretical first image of the current step based on the deformed rule from the step theoretical first image of the last step to the deformed image of the last step, or is an image formed by deforming the step theoretical first image of the current step based on the deformed rule from the theoretical full domain of the last step to the deformed full domain of the last step. Thus, the reference image is deformed by the deformed rule of the last step, so that when the feature point pairs are selected at each step, the actual feature points and the reference feature points are closer, thereby facilitating the selection or determination of the feature point pairs, and the error rate of determining the feature point pairs is reduced.

[0099] Compared with the embodiment three, the embodiment four can avoid the problem that after the corresponding to-be-printed patterns of two adjacent to-be-printed parts are printed, the pattern misalignment occurs between the two parts, and the continuity of the patterns superimposed along the step direction is better.

Claims

1. A method for overprinting a second pattern on a printing medium having a first pattern; wherein: The overprinting method includes a process of forming a pattern to be printed corresponding to a first pattern on a printing medium and a process of printing the pattern to be printed on the printing medium; The process of forming a pattern to be printed corresponding to the first pattern on the printing medium includes: Step S1: Acquire an image of a printing medium to form an actual image; Step S2: determining a plurality of feature point pairs on the actual image and the reference image, so that all reference feature points form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping on the reference image; Step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to coincide with corresponding actual feature points; Step S4: Determine whether there is a feature sub-point pair. If not, all deformation regions are combined to form a deformation domain and step S6 is executed. If so, each deformation region with a deformation feature sub-point is divided into polygonal deformation sub-regions based on the deformation feature sub-points and step S5 is executed. Step S5: deform all deformed sub-regions so that all deformed feature sub-points are deformed to coincide with the corresponding actual feature sub-points, and each deformed sub-region is marked as a new deformed region, and then return to step S4 or form a deformed full domain from all deformed regions and execute step S6; Step S6: deforming the second pattern to form a pattern to be printed based on the deformation rule from the reference full domain to the deformed full domain; In which, the reference image is a theoretical image of the first pattern; the feature point pairs include actual feature points located on the actual image and reference feature points correspondingly located on the reference image; the feature sub-point pairs include deformed feature sub-points located in the deformed area and actual feature sub-points correspondingly located on the actual image, the distance between which exceeds a threshold; the reference domain is formed by all reference areas.

2. The overprinting method according to claim 1, wherein: The reference area is a quadrilateral, and the deformed sub-area is a triangle.

3. The overprinting method according to claim 1, wherein: In step S2, when determining the feature point pair, one of the actual image and the reference image is a semi-transparent image and covers the other; in step S4, when judging whether there is a feature sub-point pair, one of the deformed domain and the actual image is a semi-transparent image and covers the other.

4. The overprinting method according to claim 1, wherein: In step S2, feature point pairs are determined one by one.

5. The overprinting method according to claim 1, wherein: In step S2, when determining the feature point pairs, the entire reference domain is also made to cover the theoretical area to be taken; wherein, the theoretical area to be taken refers to the area in the theoretical image of the first pattern corresponding to the part to be used after printing is completed.

6. The overprinting method according to claim 5, wherein: In step S2, when determining feature point pairs, several feature point pairs are first selected. If the reference domain formed by the selected feature point pairs does not cover the theoretical area to be taken, at least some of the feature point pairs are moved so that the reference domain covers the theoretical area to be taken.

7. The overprinting method according to claim 1, wherein: Step S6 includes deforming the reference peripheral image to form a deformed peripheral image based on the deformation rule from the reference global domain to the deformed global domain, and deforming the second pattern to form a pattern to be printed based on the deformation rule from the reference image to the deformed image; wherein the reference peripheral image is the portion of the reference image not covered by the reference global domain; and the deformed image is formed by the deformed global domain and the deformed peripheral image.

8. A method for overprinting a second pattern on a printing medium having a first pattern; wherein: The overprinting method includes a process of stepwise forming a pattern to be printed corresponding to a portion to be printed of a printing medium and a process of stepwise printing the pattern to be printed on the portion to be printed; The process of forming a pattern to be printed corresponding to the portion to be printed of the printing medium step by step each time includes: Step S1: obtaining an image of a portion to be printed on a printing medium to form an actual image; Step S2: determining a plurality of feature point pairs on the actual image and the reference image, so that all reference feature points form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping on the reference image; Step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to coincide with corresponding actual feature points; Step S4: Determine whether there is a feature sub-point pair. If not, all deformation regions are combined to form a deformation domain and step S6 is executed. If so, each deformation region with a deformation feature sub-point is divided into polygonal deformation sub-regions based on the deformation feature sub-points and step S5 is executed. Step S5: deform all deformed sub-regions so that all deformed feature sub-points are deformed to coincide with the corresponding actual feature sub-points, and each deformed sub-region is marked as a new deformed region, and then return to step SB4 or form a deformed full domain from all deformed regions and execute step S6; Step S6: deforming the reference peripheral image to form a deformed peripheral image based on the deformation rule from the reference full domain to the deformed full domain, and deforming the stepped second image to form a pattern to be printed based on the deformation rule from the reference image to the deformed image; The reference image of the first step is the theoretical first image of the first step, and the theoretical first image of each step is the entire theoretical image of the first pattern or a portion thereof corresponding to the actual image of this step; the reference image of each step other than the first step is an image formed by deforming the theoretical first image of this step based on the deformation rule from the theoretical first image of the previous step to the deformed image of the previous step; The step-by-step second image of the first step is the step-by-step theoretical second image of the first step, and the step-by-step theoretical second image of each step is the portion of the theoretical image of the second pattern corresponding to the step-by-step theoretical first image of this step; the step-by-step second image of each step other than the first step is an image formed by deforming the step-by-step theoretical second image of this step based on the deformation rule from the step-by-step theoretical first image of the previous step to the deformed image of the previous step; The feature point pairs of each step include actual feature points located on the actual image of this step and corresponding reference feature points located on the reference image of this step; the feature sub-point pairs of each step include deformed feature sub-points located in the deformed area of ​​this step and corresponding actual feature sub-points located on the actual image of this step whose distances exceed a threshold; the reference full domain of each step is formed by all reference areas of this step; the reference peripheral image of each step is the part of the reference image of this step that is not covered by the reference full domain of this step; the deformed image of each step is formed by the deformed full domain of this step and the deformed peripheral image of this step.

9. The overprinting method according to claim 8, wherein: The reference area is a quadrilateral, and the deformed sub-area is a triangle.

10. The overprinting method according to claim 8, wherein: In step S2, when determining the feature point pair, one of the actual image and the reference image is a semi-transparent image and covers the other; in step S4, when judging whether there is a feature sub-point pair, one of the deformed domain and the actual image is a semi-transparent image and covers the other.

11. The overprinting method according to claim 8, wherein: In step S2, feature point pairs are determined one by one.

12. The overprinting method according to claim 8, wherein: After the pattern to be printed is formed in each step, the pattern to be printed is printed to the corresponding portion to be printed through at least one step.

13. A method for overprinting a second pattern on a printing medium having a first pattern; wherein: The overprinting method includes a process of stepwise forming a pattern to be printed corresponding to a portion to be printed of a printing medium that was stepped last time, and a process of stepwise printing the pattern to be printed to the corresponding portion to be printed; Each step except the first step includes the following steps: Step S1: obtaining an image of the portion to be printed on the printing medium of this step to form an actual image; Step S2: determining a plurality of feature point pairs on the actual image and the reference image, so that the deformed feature points of the previous step and the reference feature points of the current step together form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping; Step S3: deforming all reference regions to form deformed regions, so that all reference feature points are deformed to deformed feature points that coincide with corresponding actual feature points; Step S4: Determine whether there is a feature sub-point pair. If not, all deformation regions are combined to form a deformation domain and step S6 is executed. If so, each deformation region with a deformation feature sub-point is divided into polygonal deformation sub-regions based on the deformation feature sub-points and step S5 is executed. Step S5: deform all deformed sub-regions so that all deformed feature sub-points are deformed to coincide with the corresponding actual feature sub-points, and each deformed sub-region is marked as a new deformed region, and then return to step S4 or form a deformed full domain from all deformed regions and execute step S6; Step S6: deforming the second stepping area of ​​the current stepping based on the deformation rule from the reference full domain to the deformed full domain to form a partial image of the current stepping, or deforming the theoretical second stepping area of ​​the current stepping based on the deformation rule from the theoretical full domain to the deformed full domain to form a partial image of the current stepping; and forming a to-be-printed pattern corresponding to the to-be-printed portion of the previous stepping based on the partial image of the current stepping and the partial image of the previous stepping; In the first step, except for step S2 and step S6, the remaining steps are the same as the corresponding steps in each other step; Step S2 of the first step: determining a plurality of feature point pairs on the actual image and the first theoretical image of the first step, so that all reference feature points form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping; Step S6 of the first step: deforming the second area of ​​the theoretical step based on the deformation rule from the theoretical full domain to the deformed full domain to form a local image of the first step; Wherein, the reference image is an image formed after the step-by-step theoretical first image of this step is deformed based on the deformation rule from the theoretical full domain of the previous step to the deformation full domain of the previous step, the step-by-step theoretical first image of each step is the whole of the theoretical image of the first pattern or a part including the part corresponding to the actual image of this step, the theoretical full domain of each step is the maximum area enclosed by the theoretical feature points on the step-by-step theoretical first image of this step, and the theoretical feature point of each step is the point on the step-by-step theoretical first image of this step corresponding to the reference feature point of this step; the reference full domain of each step is formed by the reference area of ​​this step; the feature point pair of each step includes the actual feature point located on the actual image of this step and the reference feature point correspondingly located on the reference image of this step; the feature sub-point pair of each step includes the deformed feature sub-point located in the deformation area of ​​this step and the actual feature sub-point correspondingly located on the actual image of this step, whose distance between each other exceeds a threshold; The second stepping area of ​​each step is the area formed after the theoretical second stepping area of ​​this step is deformed based on the deformation rules from the theoretical full domain of the previous step to the deformation full domain of the previous step. The theoretical second stepping area of ​​each step is the area in the theoretical second image of this step corresponding to the theoretical full domain of this step. The theoretical second image of each step is the part of the theoretical image of the second pattern corresponding to the theoretical first image of this step.

14. The overprinting method according to claim 13, wherein: In step S2 of the first step, when determining the feature point pair, one of the actual image and the first theoretical image of the step is a semi-transparent image and covers the other; in step S2 of each step except the first step, when determining the feature point pair, one of the actual image and the reference image is a semi-transparent image and covers the other; in step S4, when judging whether there is a feature sub-point pair, one of the deformed global image and the actual image is a semi-transparent image and covers the other.

15. The overprinting method according to claim 13, wherein: In step S2 of each step, feature point pairs are determined one by one.

16. The overprinting method according to claim 13, wherein: In step S2 of each step except the first step, when determining the feature point pairs, the number of reference feature points is made the same as the number of adjacent deformation feature points and each reference feature point is distributed along the width direction perpendicular to the step direction, and the deformation feature points of the previous step used to form the reference area are all the adjacent deformation feature points of the previous step; wherein, the adjacent deformation feature points of each step are part or all of the theoretical first image of the step close to the current step along the step direction among all the deformation feature points of the previous step.

17. The overprinting method according to claim 16, wherein: The reference area is a quadrilateral, and the deformed sub-area is a triangle.

18. The overprinting method according to claim 17, wherein: In step S2 of the first step, when determining the feature point pairs, the first condition that there are at least two reference feature points distributed along the stepping direction on both sides of the theoretical area to be taken should be met; in step S2 of each step except the first step, when determining the feature point pairs, the second condition that there is at least one reference feature point on both sides of the area to be taken should be met; wherein, the theoretical area to be taken for each step is the area in the theoretical first image of this step corresponding to the part to be used after printing is completed, and the area to be taken for each step is the area formed after the theoretical area to be taken for this step is deformed based on the deformation rule from the theoretical full domain of the previous step to the deformed full domain of the previous step.

19. The overprinting method according to claim 18, wherein: In step S2 of the first step, when determining the feature point pairs, the feature point pairs are first selected. If the selected feature point pairs do not meet the first condition, at least part of the feature point pairs are moved until the first condition is met. In step S2 of each step except the first step, when determining the feature point pairs, the feature point pairs are first selected. If the selected feature point pairs do not meet the second condition, at least part of the feature point pairs are moved until the second condition is met.

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