Stepping overprinting method and digital printing system
By using deformation feature points to form a reference area and performing deformation rule processing in the digital printing system, the problem of misalignment of adjacent patterns to be printed is solved, and efficient pattern alignment and overprinting effects are achieved, which is suitable for soft media such as fabrics.
Patent Information
- Application Number
- CN202511131898.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-13
- Publication Date
- 2025-10-17
AI Technical Summary
In the prior art, patterns of adjacent to-be-printed portions are easily misaligned during the overprinting process, making it difficult to achieve efficient pattern alignment.
By using the deformation feature points from the previous step and the reference feature points for the current step to form a reference area during each step, and deforming the local image based on deformation rules, the pattern alignment for each step is ensured. The computer and camera in the digital printing system assist in feature point selection and deformation processing.
It effectively avoids the misalignment of adjacent patterns to be printed, improves the overprinting effect and efficiency, simplifies the deformation process, and adapts to the deformation requirements of soft media such as fabrics.
Smart Images
Figure CN120797438A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of digital printing, in particular to a step-and-repeat method and a digital printing system. BACKGROUND
[0002] In the prior art, a pattern can be printed on a printing medium, which is generally a fabric, by a digital inkjet printing technology. A special digital inkjet printing is to print a second pattern on a printing medium which already has a first pattern. However, since the printing medium as a fabric is soft and easy to deform, the second pattern needs to be deformed accordingly so as to obtain a better effect when the second pattern is printed on the actual first pattern.
[0003] In the prior art, an existing step-and-repeat method includes finding a plurality of printing 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.
[0004] In the prior art, there are digital inkjet printing machines and printing methods that step-and-repeat to print a pattern on a printing medium which is continuous along a stepping direction. Each time the printing medium steps, an actual image of a corresponding to-be-printed part on the printing medium is obtained, and a corresponding second pattern is deformed based on the actual image and then printed on the to-be-printed part. Using the above prior art, the two adjacent to-be-printed parts are prone to misalignment after printing the corresponding to-be-printed patterns. SUMMARY
[0005] The present application aims to overcome the above-mentioned defects or problems in the background art, and to provide a step-and-repeat method and a digital printing system, which, compared with the prior art, are less prone to misalignment between two adjacent to-be-printed parts after printing the corresponding to-be-printed patterns, or provide a material basis for solving the above-mentioned problems.
[0006] To achieve the above-mentioned purpose, the following technical solutions are adopted: The first technical solution relates to a step-by-step overprinting method for overprinting a second pattern on a printing medium having a first pattern; the step-by-step overprinting method includes a process of step-by-step forming a pattern to be printed corresponding to the portion to be printed of the printing medium of the previous step and a process of step-by-step printing the pattern to be printed to the corresponding portion to be printed; each step except the first step includes the following steps: step 1: obtaining an image of the portion to be printed of the printing medium of this step to form an actual image; step 2: 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 this step together form a polygonal reference area or mutually form a polygonal reference area; At least two continuous and non-overlapping polygonal reference areas; step 3: deforming all reference areas to form deformed areas, so that all reference feature points are deformed to deformed feature points that coincide with corresponding actual feature points; step 4: deforming the second step area of this step based on the deformation rule from the reference full domain to the deformed full domain to form a local image of this step, or deforming the theoretical second step area of this step based on the deformation rule from the theoretical full domain to the deformed full domain to form a local image of this step; and forming a to-be-printed pattern corresponding to the to-be-printed portion of the previous step based on the local image of this step and the local image of the previous step; in the first step, except for steps 2 and step 4, Except step 4, the remaining steps are the same as the corresponding steps of each other step; step 2 of the first step: determine several pairs of feature points on the actual image and the first step 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 with each other; step 4 of the first step: based on the deformation rule from the theoretical full domain to the deformed full domain, the second step theoretical area is deformed to form a local image of this step; wherein, the reference image is the image formed after the deformation of the first step theoretical image of this step based on the deformation rule from the theoretical full domain of the previous step to the deformed full domain of the previous step, and the step theoretical image of each step The first image is the entire theoretical image of the first pattern or includes a portion 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 theoretical first image of this step. The theoretical feature point of each step is the point on the 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 deformed full domain of each step is formed by the deformed area of this step. The feature point pair of each step includes the actual feature point on the actual image of this step and the reference feature point corresponding to the reference image of this step.The step-second area of each step is an area formed by deforming the theoretical global area of the current step based on the deforming rule from the theoretical global area of the last step to the deformed global area of the last step, the step-theoretical second area of each step is an area corresponding to the theoretical global area 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 of the theoretical image of the second pattern corresponding to the step-theoretical first image of the current step.
[0007] The second technical solution is based on the first technical solution, wherein in step 2 of each step except the first step, when determining the feature point pairs, the number of reference feature points is the same as 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 last step used to form the reference area are all the adjacent deformed feature points of the last step; wherein 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.
[0008] The third technical solution is based on the second technical solution, wherein the reference area is a quadrilateral.
[0009] The fourth technical solution is based on the third technical solution, wherein in step 2 of the first step, when determining the feature point pairs, the first condition that both sides of the theoretical to-be-taken area have at least two reference feature points distributed along the step direction should be met; in step 2 of each step except the first step, when determining the feature point pairs, the second condition that both sides of the to-be-taken area have at least one reference feature point should be met; wherein the theoretical to-be-taken area of each step is an area corresponding to the part to be used after printing in the step-theoretical first image of the current step, and the to-be-taken area of each step is an area formed by deforming the theoretical global area of the current step based on the deforming rule from the theoretical global area of the last step to the deformed global area of the last step.
[0010] The fifth technical solution is based on the fourth technical solution, wherein in step 2 of the first step, when determining the feature point pairs, first, the feature point pairs are selected, and if the selected feature point pairs do not meet the first condition, at least part of the feature point pairs is moved until the first condition is met; in step 2 of each step except the first step, when determining the feature point pairs, first, the feature point pairs are selected, and if the selected feature point pairs do not meet the second condition, at least part of the feature point pairs is moved until the second condition is met.
[0011] The sixth technical solution is based on the first technical solution, wherein in step 2 of the first step, when determining the feature point pairs, one of the actual image and the step-theoretical first image is a semi-transparent image and is overlaid on the other; in step 2 of each step except the first step, when determining the feature point pairs, one of the actual image and the reference image is a semi-transparent image and is overlaid on the other.
[0012] The seventh technical solution is based on the sixth technical solution, wherein, in step 2 of each step, the feature point pairs are determined one by one.
[0013] The eighth technical solution relates to a digital printing system for implementing the step-by-step superimposition method as described in the first technical solution, the digital printing system comprising: a digital printer comprising a step-by-step feeding unit and a printing unit, the step-by-step feeding unit being used to step-by-step feed the printing medium and send a step signal after each step is completed, the printing unit being used to step-by-step receive the to-be-printed pattern and print the to-be-printed pattern onto the corresponding to-be-printed part of the printing medium; a camera arranged upstream of the printing unit along the step direction and used to acquire the image of the to-be-printed part of the printing medium after the step signal is received and output the actual image; and a computer connected in signal with the digital printer and the camera and comprising an input unit, a display unit and a calculation unit, the input unit being used to acquire the theoretical image of the first pattern and the theoretical image of the second pattern, further used to acquire the step signal from the step-by-step feeding unit, further used to acquire the actual image from the camera in each step, and further used to select a plurality of feature point pairs from the actual image and the first display image by the operator in each step; the display unit displays the actual image and the first display image in each step for the operator to select a plurality of feature point pairs; the calculation unit judges whether it is the first step after receiving the step signal; if it is the first step, the calculation unit generates the first display image based on the step-by-step theoretical first image of the first step and sends it to the display unit, and forms a polygonal reference area or at least two polygonal reference areas which are continuous with each other and do not overlap based on all the reference feature points of the current step in the plurality of feature point pairs selected by the operator, the calculation unit further executes the step 3 and the step 4 of the first step to form the local image of the current step; if it is not the first step, the calculation unit generates the first display image based on the reference image of the current step and sends it to the display unit, and forms a polygonal reference area or at least two polygonal reference areas which are continuous with each other and do not overlap based on the reference feature points of the current step and the deformed feature points of the last step in the plurality of feature point pairs selected by the operator, the calculation unit further executes the step 3 and the step 4 of each step except the first step to form the to-be-printed pattern corresponding to the to-be-printed part of the last step and send it to the printing unit.
[0014] Compared with the prior art, the above-mentioned solution has the following beneficial effects: In the prior art, the reason for the pattern misalignment between two adjacent to-be-printed parts after printing the corresponding to-be-printed patterns is that the to-be-printed patterns corresponding to each to-be-printed part are formed based on the respective actual images. In the forming process, since the reference area that needs to be deformed cannot be expanded to the joint of the two to-be-printed parts, the deformation rule of the reference area can only be expanded to the peripheral image, so the deformation of the peripheral image is fitted by the deformation of the reference area, which causes the to-be-printed patterns of the adjacent to-be-printed parts to be prone to misalignment.
[0015] In the first technical solution, in each step except the first step, a polygon reference area is formed by the deformed feature points of the last step and the reference feature points of the current step, or at least two polygon reference areas that are continuous and do not overlap with each other, to deform the reference image of the current step, and to form the 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. Since in each step, all the deformed areas and reference areas are connected to each other along the stepping direction, and the corresponding to-be-printed part is formed in the current step only after the deformation of all the reference areas corresponding to the to-be-printed part of the last step, the to-be-printed patterns corresponding to two adjacent to-be-printed parts will not be misaligned, and therefore a better superimposition effect can be obtained.
[0016] In the second to fifth technical solutions, the reference full area can span the to-be-taken area in the width direction, so there is no need to deform the peripheral images on both sides, and therefore the deformation is simpler and more efficient.
[0017] In the third technical solution, the reference area is a quadrilateral, which is more easily deformed once by using two-dimensional affine transformation or local deformation function (such as bilinear interpolation, bicubic interpolation, etc.), and is suitable for the overall deformation of a printing medium with a large scale.
[0018] In the sixth technical solution, when the feature point pairs are determined, one of the actual image and the reference image or the stepping theoretical first image is a semi-transparent image, which is overlaid on the other, so that the feature point pairs can be more intuitively observed and selected.
[0019] The prior art is to first select the actual feature points in all actual images, and then select the reference feature points on the reference images 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. The seventh technical solution limits the selection of feature point pairs one by one, so that the person can directly select the actual feature points and the reference feature points with no doubt about the correspondence, and give up the correspondence between the actual feature points and the reference feature points that are difficult to determine, and determine whether there are feature sub-point pairs after one deformation, so that the determination is easier and less prone to errors.
[0020] The eighth technical solution provides a digital printing system for realizing the digital overprinting method in the first technical solution, and has technical effects equivalent to those of the first technical solution. BRIEF DESCRIPTION OF DRAWINGS
[0021] In order to more clearly illustrate the technical solutions of the embodiments, the following briefly introduces the drawings needed to be used: Figure 1 Theoretical image of the first pattern in the embodiment; Figure 2 Theoretical image of the second pattern in the embodiment; Figure 3 The overprinting effect expected to be achieved in the embodiment; Figure 4 Actual image acquired in step S1 of the first stepping in the embodiment; Figure 5 Schematic diagram of step S2 of the first stepping in the embodiment Figure 1 ; Figure 6 Schematic diagram of step S2 of the first stepping in the embodiment Figure 2 ; Figure 7 Schematic diagram of step S3 of the first stepping in the embodiment; Figure 8 Actual image acquired in step S1 of each stepping except the first stepping in the embodiment; Figure 9 Schematic diagram of step S2 of each stepping except the first stepping in the embodiment Figure 1 ; Figure 10 Schematic diagram of step S2 of each stepping except the first stepping in the embodiment Figure 2 ; Figure 11 Schematic diagram of step S3 of each stepping except the first stepping in the embodiment; Figure 12 Overprinting effect after step S6 of each stepping except the first stepping in the embodiment; Figure 13 Structural schematic diagram of the digital printing system in the embodiment.
[0022] Main reference signs: 1, digital printing system; 2, digital printing machine; 3, camera; 4, computer; 5, stepping supply unit; 6, printing unit; 7, input unit; 8, display unit; 9, calculation unit; 10, printing medium; 11, stepping direction. DETAILED DESCRIPTION
[0023] 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.
[0024] In the claims and specification, the terms "comprises", "comprising", "has", "having", and the like, are meant to be open-ended and do not limit the described implementations to the precise configurations read into such terms.
[0025] In the claims and specification, the term "comprises" means "includes but not limited to" unless otherwise specified.
[0026] Embodiment One The step-and-repeat method in this embodiment is used to repeat a second pattern on a print medium with a first pattern. Referring to Figure 1 、 Figure 2 and Figure 3 , Figure 1 a theoretical image of the first pattern in this embodiment is shown. Figure 2 a second pattern in this embodiment is shown. Figure 3 a desired effect of repeating the second pattern on the first pattern in this embodiment is shown. The print medium in this embodiment is a fabric, and 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 unevenness before and during printing. Therefore, the second pattern needs to be deformed to correspond to the first pattern on the real print medium, so as to obtain a better repeating effect.
[0027] The step-and-repeat method in this embodiment includes a process of step-by-step forming a to-be-printed pattern corresponding to a to-be-printed part of the print medium in the last step, and a process of step-by-step printing the to-be-printed pattern to the corresponding to-be-printed part. After the to-be-printed pattern corresponding to the to-be-printed part is formed, it can be printed to the corresponding to-be-printed part in this step, or it can be printed to the to-be-printed part after at least one step. In this embodiment, after the to-be-printed pattern corresponding to the to-be-printed part is formed, it is printed to the corresponding to-be-printed part in this step.
[0028] In this embodiment, the first step includes the following steps: Step S1: obtaining an actual image of the to-be-printed part of the print medium; The actual image of the to-be-printed part of the print medium is obtained from a camera. The camera is located upstream of the printing unit of the printer in 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 4 .
[0029] Step S2: determining a plurality of feature point pairs on the actual image and the first step 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; 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.
[0030] like Figure 5 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 5 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.
[0031] like Figure 6As 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.
[0032] 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 7 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.
[0033] Step S4: forming a partial image of the first step by deforming the second area of the theory step based on the deformation rule from the theoretical full domain to the deformed full domain; Among them, the theoretical domain is the largest area enclosed by the theoretical feature points on the step-theoretical first image of this step, and the theoretical feature points are the points on the step-theoretical first image of this step corresponding to the reference feature points of this step; the deformation domain is formed by all the deformation areas of this step; the step-theoretical second area is the area in the step-theoretical second image of this step corresponding to the theoretical domain of this step, and the step-theoretical second image is the part of the theoretical image of the second pattern corresponding to the step-theoretical first image of this step.
[0034] Step S6 is performed by running a computer program.
[0035] In this embodiment, each step except the first step includes the following steps: Step S1: obtaining an image of a portion to be printed on a printing medium to form an actual image; Figure 8 The actual image of the second step of this embodiment is shown.
[0036] 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 continuous and non-overlapping polygonal reference areas; The reference image is an image formed by deforming the theoretical first image of the current step based on the deformation rule from the theoretical full domain of the previous step to the deformation full domain of the previous step.
[0037] like Figure 9As 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.
[0038] like Figure 9 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 9 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.
[0039] like Figure 9 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.
[0040] like Figure 10As 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.
[0041] 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 11 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.
[0042] 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.
[0043] 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 12 shown.
[0044] The step-by-step overprinting method in this embodiment is as follows Figure 13 The digital printing system 1 shown is implemented. Figure 13 As shown, the digital printing system 1 includes a digital printing machine 2 , a camera 3 and a computer 4 .
[0045] Among them, the digital printing machine 2 includes a stepping supply unit 5 and a printing unit 6. The stepping supply unit 5 is used to stepwise supply the printing medium 10 along the stepping direction 11 and send a stepping signal after each step is completed. The printing unit 6 is used to stepwise receive the pattern to be printed and print the pattern to be printed to the corresponding part to be printed on the printing medium 10.
[0046] The camera 3 is arranged upstream of the printing unit 6 along the stepping direction 11 and is used to obtain an image of the to-be-printed portion of the printing medium 10 and output the actual image after receiving the stepping signal.
[0047] Computer 4 is signal-connected to the digital printing machine 2 and camera 3 and includes an input unit 7, a display unit 8, and a calculation unit 9. Input unit 7 is used to obtain theoretical images of the first and second patterns, as well as to obtain stepping signals from the stepping supply unit 5. It is also used to obtain actual images from camera 3 during each step, and to allow an operator to select several feature point pairs from the actual image and the first display image during each step. Display unit 8 displays the actual image and the first display image during each step, allowing the operator to select several feature point pairs. After receiving the stepping signals, calculation unit 9 determines whether it is the first step. If so, calculation unit 9 generates a first display image based on the theoretical first image of the first step and sends it to display unit 8. It also generates a polygonal reference area or at least two continuous and non-overlapping polygonal reference areas based on all reference feature points of the current step in the several feature point pairs selected by the operator. The calculation unit 9 also performs step 3 and step 4 of the first step to form a partial image of the current step. If it is not the first step, the calculation unit 9 generates a first display image based on the reference image of this step and sends it to the display unit 8, and forms a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping based on the reference feature points of this step among several feature point pairs selected by the operator. The calculation unit also executes step 3 and step 4 for each step except the first step to form a pattern to be printed corresponding to the part to be printed in the last step and sends it to the printing unit 6.
[0048] In this embodiment, in each step except the first step, the deformation feature points of the previous step and the reference feature points of the current step are used to form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping with each other, so as to deform the reference image of the current step, and based on the local image of the current step and the local image of the previous step, a pattern to be printed corresponding to the part to be printed of the previous step is formed. Since in each step, all the deformation areas and the reference areas are connected to each other along the step direction, and the corresponding part to be printed is formed in the current step only after all the reference areas corresponding to the part to be printed of the previous step are deformed, the patterns to be printed corresponding to two adjacent parts to be printed will no longer be misaligned, so that a better overprinting effect can be obtained.
[0049] In this embodiment, the entire reference region is allowed to span the area to be acquired along the width direction, so there is no need to deform the peripheral images on both sides, making the deformation simpler and more efficient.
[0050] In this embodiment, the reference area is a quadrilateral, which makes it easier to achieve a one-time deformation using a two-dimensional affine transformation or a local deformation function (such as bilinear interpolation, bicubic interpolation, etc.), so as to adapt to a larger-scale overall deformation of the printing medium.
[0051] In the embodiment, when determining the feature point pair, one of the actual image and the reference image or the first image of the step theory is a semi-transparent image, and is overlaid on the other, so that a person can more intuitively observe and select the feature point pair.
[0052] In the embodiment, the feature point pair is selected one by one, so that a person can directly select the actual feature point and the reference feature point with no doubt about the corresponding relationship, and abandon the corresponding relationship of the actual feature point and the reference feature point which is difficult to determine, and determine whether the feature sub-point pair exists after one deformation, so that the determination is easier and less prone to error.
[0053] The above description of the specification and the embodiments is used to explain the protection scope of the present application, but does not constitute a limitation on the protection scope of the present application.
Claims
1. A step-by-step overprinting method for overprinting a second pattern on a printing medium having a first pattern; wherein: The step-by-step overprinting method includes a process of step-by-step 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 step-by-step printing the pattern to be printed to the corresponding portion to be printed; Each step except the first step includes the following steps: Step 1: Acquire the image of the portion to be printed of the printing medium of this step to form an actual image; Step 2: Determine a number 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 continuous and non-overlapping polygonal reference areas; Step 3: 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 4: deforming the second region of the current step based on the deformation rule from the reference full domain to the deformed full domain to form a partial image of the current step, or deforming the theoretical second region of the current step based on the deformation rule from the theoretical full domain to the deformed full domain to form a partial image of the current step; and forming a to-be-printed pattern corresponding to the to-be-printed portion of the previous step based on the partial image of the current step and the partial image of the previous step; In the first step, except for step 2 and step 4, the remaining steps are the same as the corresponding steps of each other step; Step 2 of the first step: determining a plurality of feature point pairs on the actual image and the first step 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 4 of the first step: forming a local image of this step by deforming the second region of the step theory based on the deformation rule from the theoretical full domain to the deformed full domain; Among them, the reference image is the image formed after the 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 theoretical first image of each step is the whole of the theoretical image of the first pattern or a part of 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 theoretical first image of this step. The theoretical feature point of each step is the point on the 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 variation of each step is The shape domain is jointly formed by the deformed 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 step second area of each step is the area formed after the step theoretical second area of this step is deformed based on the deformation rule from the theoretical domain of the previous step to the deformed domain of the previous step, the step theoretical second area of each step is the area in the step theoretical second image of this step corresponding to the theoretical domain of this step, and the step theoretical second image of each step is the part in the theoretical image of the second pattern corresponding to the step theoretical first image of this step.
2. The step-by-step overprinting method according to claim 1, wherein: In step 2 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 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 adjacent deformed feature points of the previous step; wherein, the adjacent deformed 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 deformed feature points of the previous step.
3. The step-by-step overprinting method according to claim 2, wherein: The reference area is a quadrilateral.
4. The step-by-step overprinting method according to claim 3, wherein: In step 2 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 2 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.
5. The step-by-step overprinting method according to claim 4, wherein: In step 2 of the first step, when determining the feature point pairs, first select the feature point pairs, and if the selected feature point pairs do not meet the first condition, move at least part of the feature point pairs until the first condition is met; In step 2 of each step except the first step, when determining the feature point pairs, first select the feature point pairs. 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.
6. The step-by-step overprinting method according to claim 1, wherein: In step 2 of the first step, when determining the feature point pair, one of the actual image and the theoretical first image of the step is a semi-transparent image and covers the other; in step 2 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.
7. The step-by-step overprinting method according to claim 6, wherein: In step 2 of each step, the feature point pairs are determined one by one.
8. A digital printing system for implementing the step-by-step overprinting method according to claim 1, characterized in that: The digital printing system includes: A digital printing machine comprising a step-by-step feeding unit and a printing unit, wherein the step-by-step feeding unit is used to feed a printing medium step by step and send a step signal after each step is completed, and the printing unit is used to step by step receive a pattern to be printed and print the pattern to be printed on a corresponding portion to be printed on the printing medium; a camera disposed upstream of the printing unit in the stepping direction and configured to acquire an image of the portion to be printed of the printing medium and output an actual image after receiving the stepping signal; and A computer is connected to a digital printing machine and a camera signal and includes an input unit, a display unit and a calculation unit, wherein the input unit is used to obtain a theoretical image of a first pattern and a theoretical image of a second pattern, and is also used to obtain a step signal from a step supply unit, and is also used to obtain an actual image from the camera in each step, and is also used to allow an operator to select a number of feature point pairs from the actual image and the first display image in each step; the display unit displays the actual image and the first display image in each step for the operator to select a number of feature point pairs; the calculation unit determines whether it is the first step after receiving the step signal; if it is the first step, the calculation unit generates a first display image based on the first theoretical step image of the first step and sends it to the display unit, and generates a first display image based on the number of feature point pairs selected by the operator All the reference feature points of this step form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping with each other, and the computing unit further executes step 3 and step 4 of the first step to form a local image of this step; if it is not the first step, the computing unit generates a first display image based on the reference image of this step and sends it to the display unit, and based on the reference feature points of this step among several feature point pairs selected by the operator and the deformation feature points of the previous step, together form a polygonal reference area or at least two polygonal reference areas that are continuous and non-overlapping with each other, and the computing unit further executes step 3 and step 4 of each step except the first step to form a pattern to be printed corresponding to the part to be printed of the previous step and sends it to the printing unit.