Image recognition method and system for printing

Abstract

An image recognition method for printing on rigid substrates is described, comprising the steps of: defining a digital graphic design (P_G_DGT) representative of a rigid substrate to be produced; spreading a soft layer (SL) of granular or powdery ceramic material on a deposition surface (P); compacting the soft layer (SL) to obtain a compacted layer (CL); acquiring a real image (I REAL ) of the compacted layer (CL) after the compacting step; detecting key points (KPi REAL ) of the real image (I REAL ); comparing the key points (KPi REAL ) of the real image (I REAL ) with key points (KPi_pred) of an image (I_G_DGT) obtained / derived from the predefined digital graphic design (P_G_DGT); and calculating a portion (I_P_G_DGT) of said digital graphic design (P_G_DGT) corresponding to a portion (P_I REAL ) of the acquired real image (I REAL ). The invention also comprises an image recognition system for printing and a corresponding printing method / system for implementing the described method.

Description

[0001] Description

[0002] Field of application

[0003] The present invention relates to an image recognition method and system for printing on a rigid substrate.

[0004] In particular, the present invention relates to an image recognition method and system for printing on a rigid substrate, in particular a ceramic or glass substrate, and more in particular a tile or a slab.

[0005] More in particular, the present invention relates to an image recognition method and system for printing on a rigid substrate, which is suitable for receiving a printing performed on the basis of a digital graphic design. State of the art

[0006] In the ceramic production process, the raw material typically used to form the tiles is a ceramic powder or granulate, commonly referred to as atomized material. The production process typically requires spreading the atomized material on a conveyor belt or filling a mould with the atomized material, which is first compacted by a press and then fired in a high-temperature kiln in order to sinter the tile and turn it into a real ceramic product. Over the years, the technology of the tile production process has undergone significant developments, whereby the size of the traditional tiles has become increasingly larger, also due to market demand.

[0007] The increase in the size of the tiles has led to the product resulting from the new production process being identified with the term ceramic slab, which is precisely considering the larger size of the production, which can have a width of up to 1800 mm, a length of up to 4800 mm and a thickness of up to 30 mm. The term ceramic slab is to be understood as equivalent to tile or ceramic substrate.

[0008] The production of tiles or slabs of such large size has made it possible to develop new printing technologies, which extend from the surface to the inside, throughout the entire thickness of the slab, in order to better reproduce the characteristic textures of natural stone materials such as marble or granite. An example of these printing devices is described in the publication WO2020026136 Al of the same applicant. This decoration system allows obtaining a large amount of decoration using coloured raw material or atomized material before the pressing step.

[0009] In fact, in addition to being able to obtain the surface decoration of the slab through wet digital printing technologies, such as inkjet, which are typically applied after the pressing step, it is now possible to produce a large amount of decoration using coloured ceramic powder or granulate before the pressing step.

[0010] One problem encountered with the use of the two digital decoration or printing techniques (wet inkjet printing applied after pressing and dry mass decoration applied before pressing) is the non-correspondence or imperfect superimposition of the decoration produced by each printing process before and after pressing.

[0011] The defect encountered is the discontinuity between the texture of the surface image printed, for example, by the digital printer and the texture generated within the block.

[0012] In fact, the ceramic tile or slab produced does not correspond to the desired digital graphic design, or rather, starting from the digital graphic file representing the ceramic slab to be reproduced, there is no correspondence with the real image of the slab obtained at the end of the production process, i.e. after firing of the ceramic base.

[0013] It has been observed that during the pressing step the mass decoration is deformed, which leads to the above-mentioned non-correspondence between the digital graphic design and the real image.

[0014] Also in the printing carried out on the original structured base (rigid base), the pressing step generates deformations in the base, so that the structure (i.e. the two-dimensional / three-dimensional shape of the compacted layer) output by the pressing step is no longer consistent with the structure determined by the die in the pressing step, where structure means the two-dimensional / three-dimensional shape of the compacted layer.

[0015] Also in this case, the digital image printed on the rigid base after the pressing step by the inkjet printer will no longer be consistent with the structure of the compacted layer.

[0016] Due to the slight variations in structure, the following problem arises: to make the image / structure after pressing consistent with the image / structure of the initial digital graphic design, in order to obtain the correct subsequent printing phase.

[0017] The aim of the present invention is to identify, on the basis of the initial graphic design, the correct image for printing after the pressing step, i.e. to identify the printing image that takes into account the deformations that occur in the pressing step. SUMMARY

[0019] In a first aspect, the present invention describes an image identification method for printing on a rigid base, comprising the following steps:

[0020] defining a digital graphic design representing a rigid base to be produced;

[0021] spreading a soft layer of granular or powdery ceramic material on a deposition surface;

[0022] pressing the soft layer to obtain a compacted layer;

[0023] wherein one or more of the preceding steps are performed based on the digital graphic design;

[0024] a real image of the compacted layer is acquired after the pressing step;

[0025] key points of the real image are detected;

[0026] the key points of the real image are compared with key points of an image obtained / derived from the predefined digital graphic design;

[0027] a part of the digital graphic design corresponding to a part of the acquired real image is calculated.

[0028] The recognition method preferably comprises a step of processing the digital graphic design and the real image so as to make them comparable, wherein the processing step precedes the step of comparing the key points of the real image.

[0029] The processing step preferably comprises a step of identifying one or more of the following from the real image acquired in the acquisition step:

[0030] the structure of the compacted layer resulting from the pressing step;

[0031] the amount of decoration resulting from the step of spreading the soft layer.

[0032] The structure of the compacted layer is preferably a structure with or without graphics.

[0033] The step of spreading the soft layer of granular or powdery ceramic material on the support surface preferably provides decoration throughout the thickness of the soft layer.

[0034] Preferably, the processing step comprises the following steps:

[0035] filtering one or more of the following:

[0036] the predefined digital graphic design, to determine a composite image of the graphic design;

[0037] the real image acquired in the acquisition step, to determine a composite image of the real image;

[0038] The filtering is performed in such a way as to make the predefined digital graphic design and the acquired real image comparable.

[0039] The filtering step preferably comprises applying a convolution filter and / or a gradient, and / or blurring and / or color adjustment and / or graphic adjustment.

[0040] The detection step preferably comprises detecting key points of the composite image of the real image.

[0041] Preferably, it is also envisaged to detect key points of the synthetic image of the graphic design.

[0042] The comparison step preferably comprises comparing each key point of the synthetic image of the real image with all the key points of the synthetic image of the graphic design.

[0043] The comparison step preferably comprises comparing the descriptor of each key point of the two synthetic images, wherein the descriptor comprises spatial information and neighborhood information, thereby defining a matching key point.

[0044] Preferably, a step of defining a transformation function between the real image and the digital graphic design from the relationship between the matching points is provided.

[0045] Preferably, a step of applying the transformation function to any portion of the acquired real image, thereby obtaining the portion of the digital graphic design is provided.

[0046] The portion of the digital graphic design preferably represents at least a portion of the rigid substrate.

[0047] The step of acquiring a real image of the compacted layer after the pressing step is preferably performed at the end of the pressing step.

[0048] The step of acquiring a real image of the compacted layer after the pressing step is preferably performed at the end of the cutting step.

[0049] In a second aspect, the application describes an image recognition system for printing on a rigid substrate, comprising:

[0050] A printer for bulk decoration, adapted to spread a soft layer of granular or powdery ceramic material on a deposition surface, based on a digital graphic design representative of a rigid substrate to be produced;

[0051] A pressing device adapted to press the soft layer to obtain a compacted layer;

[0052] An acquisition system adapted to acquire a real image of the compacted layer after the pressing step;

[0053] A first processing unit configured to:

[0054] Detect key points of the real image;

[0055] Compare the key points of the real image with the key points of an image obtained / derived from the digital graphic design;

[0056] Compute a portion of the digital graphic design corresponding to a portion of the acquired real image.

[0057] In a third aspect, the present application describes a method for printing on a rigid substrate, comprising the following steps:

[0058] receiving a file of an image to be printed corresponding at least to a subset of a digital graphic design;

[0059] receiving a rigid substrate on which printing is to be performed;

[0060] detecting, on the rigid substrate, a portion of the digital graphic design corresponding to a portion of a real image, according to one of the preceding aspects of the application;

[0061] wherein the image contained in the portion represents an image portion to be printed from the file of the image to be printed;

[0062] detecting a corresponding position of the portion of the real image to be printed relative to the rigid substrate;

[0063] processing the image portion to be printed so as to adapt to the portion of the real image, at least according to the detected position, thus determining a corresponding processed image portion to be printed;

[0064] repeating the following steps:

[0065] detecting, on the rigid substrate, a portion of the digital graphic design corresponding to a portion of a real image;

[0066] and

[0067] detecting a corresponding position of the portion of the real image to be printed relative to the rigid substrate for all portions forming the real image;

[0068] printing on the rigid substrate all the processed image portions to be printed.

[0069] Preferably, in the printing step, the processed image portions to be printed are in register and aligned with one or more of the following:

[0070] the structure of the compacted layer resulting in the pressing step;

[0071] the amount of decoration resulting in the step of spreading the soft layer.

[0072] In a fourth aspect, the present application describes a system for printing on a rigid substrate, comprising:

[0073] a second processing unit configured to receive a file of an image to be printed corresponding at least to a subset of a digital graphic design;

[0074] a conveyor device adapted to convey a rigid substrate on which printing is to be performed towards a decorator device;

[0075] a first processing unit of the second aspect of the application, configured to detect, on said rigid substrate, a portion of the digital graphic design corresponding to a portion of the real image;

[0076] a detection system adapted to detect the corresponding position of the portion of the real image to be printed with respect to the rigid substrate;

[0077] wherein said second processing unit is configured to process the portion of the image to be printed as a function of at least the detected position, so as to adapt to said portion of the real image;

[0078] wherein said first processing unit is configured to repeat the step of detecting, on said rigid substrate, a portion of the digital graphic design corresponding to a portion of the real image, for all the portions forming the real image;

[0079] wherein said detection system is configured to repeat the step of detecting the corresponding position of the portion of the real image to be printed with respect to the rigid substrate, for all the portions forming the real image;

[0080] said decorator device is adapted to print all the processed portions of the image on said rigid substrate.

[0081] Preferably, said processed portion to be printed is in register and aligned with one or more of the following:

[0082] said structure of the compacted layer resulting from said pressing device according to the second aspect of the application;

[0083] the mass decoration resulting from said printer for mass decoration, said printer being adapted to spread said soft layer, according to the second aspect of the application.

[0084] The present application achieves the following further technical effects:

[0085] the correspondence between the structure of the pressed rigid substrate and the digital decoration printed by the decorator device, in particular an inkjet printer;

[0086] the correspondence between the digital decoration printed by the decorator device, in particular an inkjet printer, and the mass decoration.

[0087] The aforementioned technical effects / advantages of the present application and other technical effects / advantages will emerge more clearly from the description of example embodiments set out hereinafter, given by way of illustration and not by way of limitation, with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0089] Figure 1 is a schematic view of a device for producing rigid ceramic substrates / panels according to the present application.

[0090] Figure 2A is a schematic view of a first example of rigid substrate / ceramic slab obtained during the method of the application.

[0091] Figure 2B is a cross-sectional view along the longitudinal axis of a second example of rigid substrate / ceramic slab obtained during the method of the application.

[0092] Figure 3 shows a block diagram of the recognition method of the application.

[0093] Figure 4 shows details of the block diagram in Figure 3 or Figure 1 .

[0094] Figure 5 shows a block diagram of the printing method according to the application.

[0095] Figure 6 shows a block diagram of the printing system according to the application.

[0096] Figure 7 shows details of the block diagram in Figure 6 .

[0097] Figures 8.1 to 8.10 shows the detailed steps of a particular example embodiment of the application.

[0098] detailed description

[0099] The present application describes an image recognition method for printing on a rigid substrate.

[0100] Based on a digital graphic design representative of a rigid substrate to be produced, the present application comprises producing a plurality of decorations, the plurality of decorations being pressed to obtain a compacted layer, and subsequently acquiring a real image thereof; a comparison between the key points of the real image and the key points of the image of the digital graphic design enables to identify a portion of the digital graphic design corresponding to a portion of the acquired image.

[0101] With reference to the attached drawings, and in particular to Figure 3 , the present application comprises the following step 0) : defining a digital graphic design P_G_DGT representative of a rigid substrate to be produced.

[0102] In the described process, the rigid substrate will in particular refer to a ceramic or glass substrate, more particularly to a tile or slab.

[0103] The production process comprises an initial step of preparing the rigid substrate.

[0104] In particular, with reference to Figure 1 and Figure 4 .The present application comprises the following step a) : spreading a soft layer SL of granular or powdery ceramic material on a deposition surface P.

[0105] With particular reference to Figure 1 The spreading of the soft layer SL is performed, for example, by means of the machine for mass decoration 10, 20, 30, 31 (hereinafter indicated as "machine for mass decoration 1") described in the patent application WO2020121098A1 of the same Applicant.

[0106] The soft layer SL can have one or more areas of different colour. The spreading of the soft layer determines the graphic of the rigid substrate.

[0107] As will be understood in the course of the following description, the rigid substrate comprises a compacted layer CL obtained as a result of the pressing step.

[0108] The graphic of the rigid substrate is the mass decoration mentioned above.

[0109] In one embodiment of the present application, the spreading of the soft layer SL of granular or powdery ceramic material on the deposition surface P provides for the decoration throughout the entire thickness of the soft layer SL.

[0110] With particular reference to Figure 1 The machine for mass decoration 1 is adapted to spread the soft layer SL of granular or powdery ceramic material on the deposition surface P on the basis of a digital graphic design P_G_DGT representative of the rigid substrate to be produced.

[0111] The soft layer SL is intended for the subsequent pressing step b) to obtain a compacted layer CL which is subjected to further cutting, decoration and firing steps.

[0112] The present application comprises the following step b) : pressing the soft layer SL to obtain a compacted layer CL contained in a rigid substrate.

[0113] In a possible embodiment, the deposition surface P is a movable surface which, in addition to allowing the spreading, is adapted to convey the soft layer SL to the pressing device 80.

[0114] The pressing device 80 is therefore adapted to perform said pressing step b).

[0115] For example, the pressing device 80 is in the form of a belt press known in the art for pressing large-size slabs.

[0116] With particular reference to Figure 1 This type of press comprises a lower die 81 provided with an upward facing pressing surface, while an upper die 82, provided with a downward facing pressing surface, is located above the lower die.

[0117] At least one of the two molds is movable towards and away from the other mold in order to perform the pressing of the soft layer SL.

[0118] The press further comprises a movable surface 83 in the form of a flexible belt having an active portion 84 disposed at least partially between the upper mold 82 and the lower mold 81.

[0119] The press further comprises a second movable surface 85 in the form of a flexible belt having an active portion 86 disposed between the active portion 84 of the first movable belt 83 and the upper mold 82.

[0120] In a preferred but not exclusive embodiment, the soft layer SL is transferred from the deposition surface P to the movable surface 83 of the press according to the solution described in the publication WO2017051275 in the name of the same Applicant.

[0121] According to this solution, the deposition surface P in the portion on which the soft layer SL is deposited is substantially aligned and contiguous, along the longitudinal advancement direction Y, with the active portion or output portion 84 of the movable surface 83 at a greater height, in which the front end 51 of the deposition surface P is at least partially located above the rear end 83a of the movable surface 83.

[0122] In an alternative solution, the deposition surface P extends between the molds 81, 82, i.e. there is no movable surface 83, and the pressing of the soft layer SL occurs directly on the deposition surface P.

[0123] Preferably, with particular reference to Figure 2A The soft layer SL is provided with a large number of decorations V comprising textures and / or other decorative patterns that extend from the upper surface F of the board, i.e. the surface intended to remain in the field of view after the board has been laid in place, into the thickness of the soft layer SL.

[0124] The machine 1 for a large number of decorations is adapted to precisely control the pattern of the large number of decorations V generated during the laying of the soft layer SL.

[0125] During the pressing, the pressing device 80 can determine the surface reliefs and embossings. If present, this result will be referred to as surface structure ST, as shown in Figure 2B where the dimensions of the different portions shown are not necessarily to scale.

[0126] Preferably, the rigid substrate comprising the compacted layer CL can have a large number of decorations and / or surface structure ST.

[0127] Preferably, other processes can be applied to the rigid substrate, such as the application of colored powders, colored liquids, chiseling, engraving, 3D printing or other processes.

[0128] The digital graphic design P_G_DGT comprises or represents all the features of the rigid substrate before the pressing (i.e. in relation with the bulk decoration V), after the pressing (i.e. in relation with the compacted layer CL with or without surface structure ST), and after the decoration step (in particular the digital printing).

[0129] In fact, the digital graphic design P_G_DGT represents one or more of these features: the bulk decoration V and / or the surface structure ST, and the digital printing.

[0130] These processes will produce other product features if present.

[0131] According to the invention, the mentioned bulk decoration, structure and other features are defined by the digital graphic design P_G_DGT, which makes them deterministic and repeatable.

[0132] Therefore, one or both of the steps a) and b) are performed on the basis of a predefined digital graphic design P_G_DGT.

[0133] As mentioned previously, during the spreading step a) and the pressing step b), the rigid substrate undergoes a mechanical deformation which is a priori unpredictable, which determines the deformation of the compacted layer CL and determines an imprecise correspondence with the starting digital graphic design P_G_DGT.

[0134] In other words, the real image, denoted hereafter I REAL , output from the pressing step is a deformed image compared to the image of the starting design.

[0135] According to the invention, the deformation is calculated by comparing the real image of the rigid substrate in transit with the image representative of the starting digital graphic design.

[0136] The deformation is calculated on the basis of a perspective transformation matrix which transforms the space of the real image of the rigid substrate in transit into the space of the image of the starting digital graphic design P_G_DGT.

[0137] Likewise, by applying the inverse transformation matrix to the image of the digital graphic design, it will be possible to derive a deformed image corresponding to the rigid substrate in transit (i.e. corresponding to the real image I REAL ).

[0138] With reference to Figure 1 and Figure 3 , according to the invention, there is thus provided a step c) of acquisition of the real image I REAL of the compacted layer CL after the pressing step b).

[0139] In a particular example embodiment, the result of the above-mentioned step c) is illustrated in Figure 8.1 .

[0140] The acquisition system 130 is adapted to acquire a real image I of the compacted layer CL after the pressing step REAL .

[0141] The acquisition system 130 preferably comprises one or more optical detectors (in particular cameras) of the type known in the art.

[0142] Preferably, the one or more optical detectors 130 are located downstream of the pressing apparatus 80 and upstream of the decorator apparatus 90 (in particular of the inkjet printer) Figure 1 ).

[0143] Each optical detector 130 is connected to a first processing unit 40, described below, in order to transmit the acquired real image I REAL to this first processing unit 40.

[0144] According to the present application, the acquisition can generally be performed in the time interval that falls between the pressing step b) and the decoration step (in particular the digital printing step).

[0145] In one embodiment, the acquisition occurs at the end of the pressing step b).

[0146] The technical effect achieved is to detect deformations that occur in the rigid substrate in transit compared to the predefined digital graphic design.

[0147] In another embodiment, the acquisition occurs at the end of the cutting step, i.e. in the finishing step that follows the pressing step b) and precedes the digital printing step.

[0148] The technical effect achieved is to detect deformations that occur in the rigid substrate in transit compared to the predefined digital graphic design.

[0149] In another embodiment, the acquisition occurs at the end of the pressing step b) and after the cutting step.

[0150] The technical effect achieved by the latter embodiment is even greater efficiency of the entire digital printing process.

[0151] In order to compare the real image output from the pressing step with the image of the starting digital graphic design, the present application comprises an image processing and comparison step.

[0152] For this purpose, with reference to Figure 1 , Figure 3 and with particular reference to Figure 4 , a first processing unit 40 is provided.

[0153] In the course of the present description and in the appended claims, the first electronic processing unit 40 is logically divided into different functional modules (memory modules or operating modules) that perform the described functions.

[0154] The first electronic processing unit 40 can consist of a single electronic device suitably programmed to perform the described functions, and the different modules can correspond to hardware entities and / or routine software forming part of the programmed device.

[0155] Alternatively or additionally, the functions can be performed by a plurality of electronic devices, on which the functional modules described above can be distributed.

[0156] Furthermore, the first electronic processing unit 40 can rely on one or more processors to execute the instructions contained in the memory modules; the functional modules described above can also be distributed on different local or remote computers based on the architecture of the network on which they reside.

[0157] According to the present application, the following step e0) is provided: processing the digital graphic design P_G_DGT and the real image I REAL in a comparable manner (that is, compatible for comparison) the digital graphic design P_G_DGT and the real image I REAL .

[0158] With particular reference to Figure 4 , the processing unit 40 is configured to perform step e0.

[0159] In particular, step e0) comprises a sub-step, namely identifying one or more of the following from the real image I REAL acquired in the acquisition step c):

[0160] the structure ST of the compacted layer CL produced in the compacting step b);

[0161] the plurality of decorations V produced in the step a) of spreading the soft layer SL.

[0162] The first processing unit 40 is configured to perform the described identification sub-step; in particular, the first processing unit 40 comprises a first processing module 401 configured to perform the described identification sub-step.

[0163] According to the present application, step e0) further comprises a sub-step g), namely filtering one or more of the following:

[0164] the predefined digital graphic design P_G_DGT to determine a synthetic image SINT_P of the graphic design;

[0165] the real image I REALto determine the synthetic image SINT I of the real image.

[0166] According to the application, the filtering sub-step g) is performed in a comparable manner with respect to the filtering sub-step g) of the pre-defined digital graphic design P_G_DGT and of the acquired real image I REAL The filtering sub-step g) is performed in a comparable manner with respect to the filtering sub-step g) of the pre-defined digital graphic design P_G_DGT and of the acquired real image I

[0167] Preferably, the filtering sub-step g) comprises applying a convolution filter and / or a gradient, and / or a blur and / or a color adjustment and / or a graphic adjustment.

[0168] The first processing unit 40 is configured to perform said filtering sub-step; in particular, the first processing unit 40 comprises a filter module 402 configured to perform said filtering sub-step.

[0169] According to the application, a further step d) of detecting key points KPi_ REAL of the real image I REAL is provided.

[0170] In particular, according to the application, the step d) comprises detecting key points KPi_ REAL of the synthetic image SINT I of the real image.

[0171] In particular, according to the application, the step d) comprises detecting key points KPi_pred of the synthetic image SINT P of the pre-defined digital graphic design.

[0172] The first processing unit 40 is configured to perform said detecting step d); in particular, the first processing unit 40 comprises a detection module 403 configured to perform said detecting step d).

[0173] The application comprises a step e) of comparing the key points KPi_ REAL of the real image I REAL with the key points KPi_pred of the image I_G_DGT obtained / derived from the pre-defined digital graphic design P_G_DGT.

[0174] The reference to "key points" in the literature can be found in the expired US patent No. 6711293 entitled "Method and apparatus for identifying scale invariant features in an image and use of same for locating an object in an image".

[0175] It should be understood that the key points are independent of the visual features of the image and depend, to some extent, on the position of the "object" in that image.

[0176] In other words, with particular reference to ceramic substrates, the key point is not extracted from predefined graphic features (such as specific fringes and / or mottling and / or textures) visible on the ceramic substrate, but rather represents a feature point detectable within the entire image and, therefore, not only in a specific predefined area.

[0177] In other words, as will be described below, each key point is assigned a descriptor Car_Kp comprising spatial information I_Spa and neighborhood information I_int.

[0178] The spatial information I_Spa comprises the position coordinates of the key point, while the value of the key point (i.e. the neighborhood information I_int) is derived by analyzing the hues and / or luminances and / or colors present in the neighborhood I_int of the key point.

[0179] In a particular example embodiment of the application, Figure 8.2 and Figure 8.3 the digital graphic design P_G_DGT and the image I_G_DGT are shown, respectively.

[0180] Figure 8.4 In the image I REAL of a real image I REAL and the key points KPi_pred of the image I_G_DGT.

[0181] The first processing unit 40 is configured to perform said comparison step e); in particular, the first processing unit 40 comprises a comparison module 404 configured to perform said comparison step e).

[0182] According to the application, step e) envisages comparing each key point KPi REAL of the synthetic image SINT_I of the real image with all the key points KPi_pred of the synthetic image SINT_P of the graphic design.

[0183] Each key point is assigned a descriptor Car_Kp comprising spatial information I_Spa and neighborhood information I_int.

[0184] The spatial information I_Spa comprises the position coordinates of the key point, while the neighborhood information I_int comprises values representative of the hues and / or luminances and / or colors of the key point.

[0185] The comparison step e) provides a comparison between the descriptor Car_Kp of each key point of the synthetic image SINT_I of the real image and all the descriptors Car_Kp of the synthetic image SINT_P of the graphic design.

[0186] The technical effect is to define the matching key points KP_O between the synthesized images, that is, the key points between the synthesized images that are in a homography relationship.

[0187] Generally speaking, in the literature of logic and mathematics, homography is a relationship between points in two spaces (in this particular case, two composite images as described above) such that each point in one space corresponds to one and only one point in the second space.

[0188] Specifically, the homography transformation (or transformation function) applied to the points of the composite image SINT_I makes it possible to obtain the transformed composite image SINT_P, and vice versa.

[0189] After the matching keypoint KP_O has been defined, the present invention includes the following steps h( Figure 4 The true image I is defined based on the relationship between matching keypoints KP_O. REAL The transformation function F between P_G_DGT and digital graphics design.

[0190] The first processing unit 40 is configured to perform step h); in particular, the first processing unit 40 includes a definition module 405 configured to perform step h).

[0191] Here, the present invention includes the following step f): calculating the digital graphics design P_G_DGT and the acquired real image I REAL Part of P_I REAL The corresponding part is I_P_G_DGT.

[0192] Figure 8.5 illustrates step f) in a specific example embodiment of the present invention.

[0193] In particular, Figure 8.5.1 The diagram shows a portion of the digital graphics design P_G_DGT, I_P_G_DGT (top right square), which is composed of the acquired real image I. REAL Partial P_I_ REAL (Top left square) Calculation; in this particular example, the part under consideration has a triangular shape.

[0194] In particular, Figure 8.5.2 The image IPRINT, which is to be printed on a rigid substrate, is shown as part of I_P_G_DGT.

[0195] To obtain the partial I_P_G_DGT of the digital graphics design P_G_DGT, that is, to calculate the partial P_I of the digital graphics design P_G_DGT compared with the acquired real image (IREAL), REALCorresponding to the portion I_P_G_DGT (step f), the present application envisages applying to the acquired real image I a transformation function F REAL of any portion P_I REAL .

[0196] In one embodiment, the portion P_I REAL can be the perimeter of a tile, so that this portion is a complete tile.

[0197] In an alternative embodiment, the portion P_I REAL is a subset, for example defined by 3 misaligned key points (as in the example of Figure 8.5.1 and Figure 8.5.2 ) or defined by a known Voronoi function, in which at each key point a surrounding area is created which is the portion under consideration.

[0198] The first processing unit 40 is configured to perform said calculation step f); in particular, the first processing unit 40 comprises a calculation module 406 configured to perform said calculation step f.

[0199] The portion I_P_G_DGT of the digital graphic design P_G_DGT represents at least a portion of the rigid substrate.

[0200] In other words, this portion defines the entire rigid substrate or a subset thereof.

[0201] In another aspect, the present application comprises a method for printing on a rigid substrate, with particular reference to the block diagram in Figure 5 .

[0202] This printing method is implemented by a printing system, as schematically shown in Figure 6 , provided with a second electronic processing unit 60 adapted to process image information and manage the printing operations of the processed images.

[0203] In the course of the present description and in the attached claims, the second electronic processing unit 60 is logically divided into different functional modules (memory modules or operating modules) which perform the described functions.

[0204] The second electronic processing unit 60 can consist of a single electronic device suitably programmed to perform the described functions, and the different modules can correspond to hardware entities and / or routine software forming part of the programmed device.

[0205] Alternatively or additionally, said functions can be performed by a plurality of electronic devices, on which the above-mentioned functional modules can be distributed.

[0206] Furthermore, the second electronic processing unit 60 can rely on one or more processors to execute instructions contained in the memory module; the aforementioned functional modules can also be distributed on different local or remote computers based on the network architecture in which they reside.

[0207] The method according to the invention includes (i) receiving a file I_ of images to be printed that corresponds at least to a subset of digital graphic designs P_G_DGT. PRINT .

[0208] In a specific example embodiment of the present invention, the received image I_ to be printed PRINT exist Figure 8.6 As shown in the image.

[0209] A subset means, for example, a specific channel (or layer) that constitutes one of the channels (or layers) of a digital graphics design P_G_DGT.

[0210] Special Reference Figure 6 The processing unit 60 is configured to perform the described step (i).

[0211] Specifically, the processing unit 60 includes a receiving module 601 configured to perform the described step (i). Figure 7 ).

[0212] The invention also includes the step of receiving (ii) a rigid substrate (including a compacted layer CL to be printed thereon).

[0213] The receiving step (ii) performed by the decorator device 90 (especially the printing unit) is carried out by a suitable conveying device 70 (e.g., a movable surface).

[0214] The present invention further includes the step (iii): detecting the digital graphics design P_G_DGT and the real image I on a rigid substrate. REAL Part of P_I REAL The corresponding part is I_P_G_DGT.

[0215] The detection step (iii) is performed in accordance with the content previously described in step cf of the first aspect of the invention.

[0216] In a specific example embodiment of the present invention, step cf is... Figure 8.7 As shown in the image.

[0217] The first processing unit 40 described above ( Figure 4 Perform the detection step (iii).

[0218] According to the present invention, the image contained in a portion of I_P_G_DGT represents an image from a file I_ to be printed. PRINT The part of the image to be printed (IP)PRINT .

[0219] In a particular example embodiment of the application, the image contained in the portion I_P_G_DGT is shown in Figure 8.8 .

[0220] The application also comprises a step (iv) of detecting the real image I REAL portion P_I REAL with respect to the corresponding position POS P_I REAL .

[0221] The detection system 180 is adapted to perform step (iv).

[0222] In particular, this system is described in the published patent application WO2017 / 149508 of the same applicant.

[0223] In a particular example embodiment of the application, the result of this step is shown in Figure 8.9 .

[0224] The application also comprises a step of processing (v) the image portion I_P_ REAL to be printed in order to adapt it to the portion P_I PRINT of the real image I REAL , thus determining the corresponding processed image portion I_P_ REAL to be printed. PRINT_ELAB .

[0225] In the particular example embodiment of the application shown in Figure 8.10 , the image portion I_P_ PRINT to be printed is shown in the upper left square, the portion P_I REAL of the real image I REAL is shown in the upper right square, while the image portion I_P_ PRINT to be printed, adjusted and positioned for superimposed printing, is shown in the bottom square.

[0226] With particular reference to Figure 6 , the second processing unit 60 is configured to perform the aforementioned processing step (v).

[0227] In particular, the processing unit 60 comprises a processing module 602 Figure 7 ) configured to perform the described step (v).

[0228] In essence, the second processing unit 60 is based on the deformation that occurs in the large number of decorations V during the pressing step, defined by the transformation function F, and on the detected position POS P_I REAL, modifying the image portion I_P_print to be printed.

[0229] The application envisages modifying all the portions P_I REAL of the real image I REAL repeating steps (iii), (iv) and (v).

[0230] In other words, for all the portions P_I REAL of the real image I REAL , the first processing unit 40 is configured to repeat step (iii), the detection system 180 is configured to repeat step (iv), and the second processing unit 60 is configured to repeat step (v).

[0231] As a final step, the application comprises printing (vi) all the processed image portions I_P_ PRINT_ELAB to be printed on a rigid substrate comprising a compacted layer (CL).

[0232] The decorator device 90, in particular an inkjet printer, is adapted to print all the processed image portions I_P_ PRINT_ELAB on the rigid substrate.

[0233] According to the application, the processed image portions I_P_ PRINT_ELAB to be printed are in register and aligned with the structure ST of the compacted layer CL produced in the pressing step b), as previously described.

[0234] Alternatively or additionally, the processed image portions I_P_ PRINT_ELAB to be printed are in register and aligned with the amount of decoration V produced in the step a) of spreading the soft layer SL, as previously described.

[0235] In a particular case, the term in register means superimposable or without offset.

[0236] In another particular case, the term in register means correlated.

[0237] An application has been described which comprises the recognition of an image for printing on a rigid substrate and the corresponding printing method / system.

[0238] The application achieves the following additional technical effects:

[0239] Correspondence between the structure of the rigid substrate after pressing and the digital decoration printed by the decorator device, in particular an inkjet printer;

[0240] Correspondence between the digital decoration printed by the decorator device, in particular an inkjet printer, and the amount of decoration.

Claims

1. An image recognition method for printing on rigid substrates, comprising the steps of: 0) defining a digital graphic design (P_G_DGT) representative of a rigid substrate to be produced; a) spreading a soft layer (SL) of granular or powdery ceramic material on a deposition surface (P); b) compacting the soft layer (SL) to obtain a compacted layer (CL); wherein one or more of the steps a) and b) are performed on the basis of a predefined digital graphic design (P_G_DGT); c) acquiring a real image (I REAL ) of the compacted layer (CL) after the pressing step b); d) detecting key points (KPi REAL ) of the real image (I REAL ); wherein each key point (KPi REAL ) is assigned a descriptor (Car_Kp) comprising spatial information (I_Spa) including position coordinates of the key point and neighborhood information (I_int) including values representative of the hue and / or luminance and / or color of the key point (KPi REAL ); e) comparing the keypoints (KPi_real) of the real image (I REAL ) with keypoints (KPi_pred) of an image (I_G_DGT) obtained from the predefined digital graphic design (P_G_DGT); REAL ​ f) calculating, on the basis of said comparison step, a deformation of a portion (I_P_G_DGT) of said digital graphic design (P_G_DGT) corresponding to a portion (P_I REAL ) of the acquired real image (I REAL ).

2. The recognition method according to claim 1, comprising a step e0) of processing said digital graphic design (P_G_DGT) and said real image (I REAL ) so as to enable a comparison between said digital graphic design (P_G_DGT) and said real image (I REAL ), wherein, said step e0) preceding said step e) of comparing said key points (KPi REAL ) of said real image (I REAL ).

3. The identification method according to claim 2, wherein, Said step e0) comprises a step of identifying, from said real image (I REAL ) acquired in said step c), one or more of the following: a structure (ST) of the compacted layer (CL) produced in the compacting step b); a decoration (V) produced in the step a) of spreading the soft layer (SL).

4. The identification method according to claim 3, wherein, The structure (ST) of the compacted layer (CL) is a structure with or without graphics.

5. The identification method according to any one of the preceding claims, wherein, The step of spreading a soft layer (SL) of granular or powdery ceramic material on a deposition surface (P) provides a decoration throughout the thickness of the soft layer (SL).

6. The identification method according to any one of claims 2-4, wherein, The processing step e0) comprises the steps of: g) filtering at least one of: the predefined digital graphic design (P_G_DGT) to determine a synthetic image (SINT_P) of the digital graphic design; the real image (I REAL ) acquired in said step c) to determine a synthetic image (SINT_I) of said real image; The filtering is performed in a manner that enables comparison of the predefined digital graphic design (P_G_DGT) and the acquired real image (I REAL ).

7. The identification method according to claim 6, wherein, the filtering step comprises applying a convolution filter and / or a gradient, and / or a blur and / or a color adjustment and / or a graphic adjustment.

8. The identification method according to claim 6, wherein, The detecting step d) comprises detecting keypoints (KPi) of the synthetic image (SINT_I) of the real image REAL ).

9. The recognition method according to claim 8, comprising detecting keypoints (KPi_pred) of the synthetic image (SINT_P) of the digital graphic design.

10. The identification method according to claim 9, wherein, Step e) includes taking each keypoint (KPi_) of the synthetic image (SINT_I) from the real image. REAL The key points (KPi_pred) of the composite image (SINT_P) of the digital graphic design are compared with all the key points (KPi_pred).

11. The identification method according to claim 10, wherein, The comparison step e) comprises comparing the descriptors (Car_Kp) of each keypoint of the two synthetic images, wherein the descriptors (Car_Kp) comprise spatial information (I_Spa) and neighborhood information (I_int), defining matching keypoints (KP_O).

12. The identification method of claim 11, further comprising after step e): defining a transformation function (F) between said real image (I REAL ) and said digital graphic design (P_G_DGT) according to the relationships between said matched key points.

13. The identification method of claim 12, comprising the steps of: applying said transformation function (F) to any portion (P_I REAL ) of said acquired real image (I REAL ), thereby obtaining a corresponding portion (I_P_G_DGT) of said digital graphic design (P_G_DGT) of said computing step (f).

14. The identification method of claim 13, wherein, applying one of: The portion (P_I REAL ) of the real image is defined by the perimeter of the rigid substrate, so the portion of the real image is a complete rigid support; The part (P_I REAL ) of the real image is defined by a subset of misaligned keypoints or by a known Voronoi function, where a surrounding area is created at each misaligned keypoint, which is the considered part.

15. The identification method according to claim 13 or 14, wherein, the portion (I_P_G_DGT) of the digital graphic design (P_G_DGT) represents at least a portion of the rigid substrate.

16. The identification method according to any one of claims 1 to 4, wherein, The step c) of acquiring a real image (I REAL ) of the compacted layer (CL) after the pressing step b) is performed at the end of the pressing step b).

17. The identification method according to any one of claims 1 to 4, wherein, between the step b) and the step c) further comprising a cutting step of the compacted layer.

18. An image recognition system for printing on rigid substrates, comprising: a printer (1) adapted to spread a soft layer (SL) of granular or powdery ceramic material on a deposition surface (P) on the basis of a digital graphic design (P_G_DGT) representative of a rigid substrate to be produced; a compacting device (80) adapted to compact the soft layer (SL) to obtain a compacted layer (CL); an acquisition system (130) adapted to acquire a real image (I REAL ) of the compacted layer (CL) after the compacting step; a first processing unit (40) configured to: detecting keypoints (KPi REAL ) of the real image (I REAL ); wherein each key point (KPi REAL ) is assigned a descriptor (Car_Kp) comprising spatial information (I_Spa) including position coordinates of the key point and neighborhood information (I_int) including values representative of the hue and / or luminance and / or color of the key point (KPi REAL ). The real image (I) REAL Key points (KPi_) REAL The key points (KPi_pred) of the image (I_G_DGT) obtained from the digital graphic design (P_G_DGT) are compared with those of the key points (KPi_pred). On the basis of said comparison step, a deformation of a portion (I_P_G_DGT) of the digital graphic design (P_G_DGT) corresponding to a portion (P_I REAL ) of the acquired real image (I REAL ) is calculated.

19. A method for printing on rigid substrates, comprising the steps of: (i) receiving a file (I PRINT ) of an image to be printed corresponding at least to a subset of a digital graphic design (P_G_DGT) representative of a rigid substrate to be produced; (ii) receiving a rigid substrate on which to print, and performing the steps of: spreading a soft layer (SL) of granular or powdery ceramic material on a deposition surface (P); compacting the soft layer (SL) to obtain a compacted layer (CL); (iii) detecting on said rigid substrate a portion (I_P_G_DGT) of said digital graphic design (P_G_DGT) corresponding to a portion (P_I REAL ) of the real image (I REAL ); wherein the image contained in the corresponding portion (I_P_G_DGT) represents a portion (I_P_print) of the image to be printed coming from a file (I PRINT ) of the image to be printed; (iv) Detect the real image to be printed (I REAL The portion (P_I) of the above REAL The corresponding position (POS P_I) relative to the rigid substrate REAL ); (v) processing said image portion to be printed (I_P_print) in function of at least the detected position (POS P_I REAL ) so as to adapt to said portion (P_I REAL ) of said real image (I REAL ) thereby determining a corresponding processed image portion to be printed (I_P_ PRINT_ELAB ); for all the portions (P_I REAL ) of which said real image (I REAL ) is formed, steps (iii) and (iv) are repeated; (vi) printing all the treated image portions (I_P to be printed on the rigid substrate; PRINT_ELAB ) ; wherein the detection step (iii) comprises the steps of: A real image (I REAL ) of the compacted layer (CL) is acquired after the pressing step; detecting keypoints (KPi REAL ) of the real image (I REAL ); wherein each key point (KPi REAL ) is assigned a descriptor (Car_Kp) comprising spatial information (I_Spa) including position coordinates of the key point and neighborhood information (I_int) including values representative of the hue and / or luminance and / or color of the key point (KPi REAL ); comparing the keypoints (KPi REAL ) of the real image (I REAL ) with keypoints (KPi_pred) of an image (I_G_DGT) obtained from a predefined digital graphic design (P_G_DGT); On the basis of said comparison step, a deformation of said portion (I_P_G_DGT) of the acquired real image (I REAL ) corresponding to said portion (P_I REAL ) of the digital graphic design (P_G_DGT) is calculated.

20. The method of claim 19, wherein, In said printing step, said processed image portion (I_P PRINT_ELAB ) to be printed is coordinated and aligned with one or more of: a structure (ST) of the compacted layer (CL) produced in the compacting step; a decoration produced in the step of spreading the soft layer (SL).

21. A system for printing on rigid substrates, comprising: a second processing unit (60) configured to receive a file (I PRINT ) of an image to be printed corresponding at least to a subset of digital graphic designs (P_G_DGT) representative of rigid substrates to be produced; a conveyor device (70) adapted to convey a rigid substrate on which printing is to be performed towards a decorator apparatus (90); a printer (1) adapted to lay down a soft layer (SL) of granular or powdery ceramic material on a deposition surface (P) on the basis of a digital graphic design (P_G_DGT) representative of a rigid substrate to be produced; a pressing apparatus (80) adapted to press the soft layer (SL) to obtain a compacted layer (CL); a first processing unit (40) configured to (iii) detect, on said rigid substrate, a portion (I_P_G_DGT) of said digital graphic design (P_G_DGT) corresponding to a portion (P_I REAL ) of a real image (I REAL ) a detection system (180) suitable for (iv) detecting the corresponding position (POS P_I REAL ) of said portion (P_I REAL ) of said real image (I REAL ) to be printed with respect to said rigid substrate; wherein the second processing unit (60) is configured to (v) process the image portion (I_P_print) to be printed in accordance with at least the detected position (POS P_I REAL ) so as to adapt to the portion (P_I REAL ) of the real image (I REAL ); wherein said first processing unit (40) is configured to repeat step (iii) for all portions (P_I REAL ) of said real image (I REAL ) forming said virtual image (I V). wherein said detection system (180) is configured to repeat step (iv) for all portions (P_I REAL ) of said real image (I REAL ) forming said real image (I). The decorator device (90) is adapted to print all the treated image portions (I_P PRINT_ELAB ) on the rigid substrate after the pressing step. wherein the first processing unit (40) is configured, in the detection step (iii), to: A real image (I REAL ) of the compacted layer (CL) is acquired after the pressing step; detecting keypoints (KPi REAL ) of the real image (I REAL ); wherein each key point (KPi REAL ) is assigned a descriptor (Car_Kp) comprising spatial information (I_Spa) including position coordinates of the key point and neighborhood information (I_int) including values representative of the hue and / or luminance and / or color of the key point (KPi REAL ); comparing the keypoints (KPi REAL ) of the real image (I REAL ) with keypoints (KPi_pred) of an image (I_G_DGT) obtained from a predefined digital graphic design (P_G_DGT); On the basis of said comparison step, a deformation of said portion (I_P_G_DGT) of the acquired real image (I REAL ) corresponding to said portion (P_I REAL ) of the digital graphic design (P_G_DGT) is calculated.

22. The system for printing on a rigid substrate of claim 21, wherein, the processed portion (I_P_print) to be printed is coordinated and aligned with one or more of: the structure (ST) of the compacted layer (CL) produced by the pressing apparatus (80); the decor (V) produced by the printer (1) adapted to lay down the soft layer (SL).

Images