ITPI20060057A1 - METHOD OF MANAGEMENT OF THE COLOR OF A PRINTING SYSTEM, USING THE USE OF THE COLORS ACTUALLY PRINTED FROM THE PRINTER. - Google Patents

Description

Description accompanying the patent application for industrial invention entitled: "Color management method of a printing system, by using the colors actually printed by the printer"

DESCRIPTION

The present invention relates to the technical sector relating to color management systems which allow images to be printed on supports of any kind. In particular, the invention relates to the technical sector relating to the realization of methods and systems which allow to choose and set the colors of the prints in such a way as to obtain a print whose result is known a priori.

The invention therefore concerns the technical sector relating to any printing system. In the present invention we refer generically to printing systems, meaning to include any printing system, be it related to professional, office or industrial printing. In particular, the system has considerable advantages for industrial printing systems in the ceramic, textile sector and in any other production sector that uses screen printing or similar techniques.

The present invention relates to a method for managing printing.

Methods and systems of the above type are known and widely used.

Although the known methods and systems perform their function satisfactorily, they have some drawbacks.

In particular, the known art relating to color management systems that allow you to print images on any kind of media, and / or to choose and set the colors of the prints in such a way as to obtain a print whose result is known a priori. , has some drawbacks.

Before the emergence of the digital age, quality printing operators used proprietary or closed color management systems, where all devices were integrated and calibrated with values known to work together and exclusively, i.e. each part of the system was integrated with the other parts and only with them. Those who treated the color, or the user of that device, were professional technicians

specialized, who could make these closed systems work, building a wide variety of color adaptations of a scanned image and predicting, with reasonable accuracy, what the final print result would be based on their manipulations. This solution of the known art, however, presents the problem that the real correspondence of the desired color with that actually printed by the printing system is closely linked to the personal skills of the technician, and therefore difficult to repeat and even random. Furthermore, it is necessary to train highly specialized personnel to obtain quality results, in which the desired color really corresponds to the printed color, with often high costs and times. A further drawback is related to the fact that many test prints were often required to correctly calibrate the system, with an increase in costs and printing times.

Currently digital printing requires the integration of constantly updated hardware and software. Hence the need for open color management, i.e. it is necessary to have non-closed printing systems, in which the various parts of the system can interface with each other, as the various parts of the system are designed and built to interface with a large number of for example, number of different peripherals, in order to have maximum integration between operating systems, graphics applications and peripherals, leading the major companies to discuss a new standardized color management. Basically, the open color management, in the digital field, involves the use of a computer or in any case of a CPU on which one or more different programs for display, printer management, graphics processing and so on are loaded, being said CPU or computer capable of being operationally connected to any type of printing device, and being the various programs loaded on the CPU or on the computer itself subject to work alternately or in combination with one another or one using the results of the other: for example the graphic processing program allows the graphic processing of the drawing or image or the like, and the printing program manages the communication with the printer and re-pagination of the same drawing created or modified by the graphic processing program.

A need currently felt is to reproduce the images in different peripheral colors in a constant and repeatable way.

A color management system (so-called CMS, Color Management System) is a collection of software tools, or computer programs, designed to correctly manage the various capabilities of reproducing the color of scanners, monitors, traditional printers, printing machines letterpress and color proofers to ensure consistent color throughout the print production process. Ideally, this means that the colors displayed on your monitor will accurately represent the colors of the final product. It also means that the various graphics applications, monitors and operating systems will display colors, integrating with each other, in the most consistent and homogeneous way possible.

The task of color management systems, the so-called CMS (Color Management System), is to compensate for the differences between devices belonging to the same or different categories. Basically, all CMSs make use of a reference color space, wider than that of the individual devices used in processing. A CMS has the task of reproducing the colors of a device, such as a monitor, having a wide range of colors (the so-called gamut), with a device with a smaller range of colors, such as a printing system.

In fact, according to the known art, the colorimetric space CEEXYZ has been defined which is suitable for this purpose, but more and more often it is preferred to use the colorimetric space defined by the CIE in 1976 and also known as CIELAB. This space has the advantage of having a visually more uniform color distribution than the CIEXYZ space, so it is possible to numerically quantify the difference between two different colors in a more meaningful way. The CIEXYZ colorimetric space works with three coordinates X, Y, Z, while the CIELAB colorimetric space works with the three coordinates L, a, b, also called L, a and b components, which can be calculated starting from those CIEXYZ with a simple formula mathematics.

Using this CIELAB space, a “universal” description of the color is obtained which can then be used to calculate the color components to be used with any other device. The actual conversion operation is managed by the Color Management Module (CMM), a fundamental element of any CMS, using the so-called "color profiles", a collection of data that describes the ability of a certain device to reproduce colors .

Creating a color profile involves the use of appropriate tools that are often quite expensive, which are not always available to the end user. In some cases, when high fidelity reproduction is not required, the profiles made available by the manufacturer of the device itself or by the manufacturers of the color management software can be used. Especially for the latter, however, it was practically impossible to be able to provide color profiles for all existing devices or even just for most of them; in addition, early CMSs used proprietary formats for profiles that made them usable only with that specific color management system.

A solution proposed by the known art, in particular by the ICC consortium (International Color Consortium), was the definition of a common format for color profiles, or more simply profiles that allows them to be used with different color management systems. .

A color management system (CMS) therefore helps to reduce or eliminate color matching problems and to keep these characteristics unchanged over time. The task of CMS color management systems is precisely to compensate for the differences between devices belonging to the same or different categories. Basically, all CMSs make use of a reference color space, wider than that of the individual devices used in processing. A color management system or CMS is a "translator" of the source color space of the image (such as scanner, monitor, digital camera) into the color space of the destination unit, which can be another monitor or a printing unit or the like. The CMS is nothing more than an engine that interprets the profile of a peripheral and "adapts" it or rather converts it, through appropriate operations, to another. To perform the conversion, the CMS needs both the source and destination color space information. A color conversion always takes place with the help of two profiles. For example, the RGB values read by a scanner are converted into the C1ELAB color space using the scanner profile, and from there into the RGB space of the monitor used for display or the CMYK space of the printer that will be used to produce the copies on paper, leveraging monitor and printer profiles for these conversions.

For example, the profile of a monitor is a table which, for each RGB numeric theme, provides the absolute coordinates (for example Lab) of the color produced by it, while the profile of a printer is a table which, for each combination of CMYK inks provides the absolute coordinates (for example Lab) of the color produced by that combination. Color management systems can also be used to convert colors based on the characteristics of a printing unit other than the one on which you are printing. This process of simulating another printing unit is commonly used for color proofing of jobs that will be printed on an offset press.

As in the case of the monitor, it is not possible to build all the rows of the table, because they are too many, so only some are built using a software called profiler and a measuring instrument (colorimeter or spectrophotometer). The procedure is as follows: the software prints a so-called "target" that is a series of colored squares (patches) of which the so-called recipe is known, CMYK (or RGB depending on the type of printer) or the composition or percentages of the inks needed to produce the color. These squares are measured with the measuring tool and the result is used by the profiler to produce the profile.

In practice, according to the prior art system, software is used to print the target and an instrument to measure it. The tool is connected to the computer and provides the data to the profiling software which processes them to produce the profile.

The process to create a profile of a printing system according to the known art therefore consists of the following phases:

- produce a TARGET (ie a set of colored cards) on the chosen support by means of the specific printing system

- measure the printed target using the measuring instrument

- use the profiling software to produce, by means of numerical techniques of interpolation of the measured values, the ICC profile, containing a three-dimensional table (called CLUT) of correspondence between CIE Lab values and the percentages of inks necessary to produce the equivalent color ( i.e. the so-called recipe).

A drawback is that the ICC profile, being the result of an "interpolation", is not necessarily true, in fact an interpolation often generates ICC profiles that appear to be correct, but which instead produce absolutely incorrect printing results.

The drawback is represented by the fact that any printing system produces inaccurate results, i.e. the result obtained is not uniform or consistent between what is shown on the screen and what is actually printed, because the printing process is affected, for example, by variations in the pigments, substrates, environmental factors, such as temperature and humidity, as well as any other factor that varies over time. It follows that the color displayed on the screen will not be the one actually printed and that even the color produced, once printed, may present some alterations compared to the initial color.

A solution proposed by the known art in particular is the well-known ICC system which consists in the creation of a three-dimensional table called "CLUT" which contains a series of formulations of the percentages of the inks necessary to produce the specific color (referred to in the continuation of the also description "recipes") which are not all actually corresponding to the desired color. In fact, the so-called CLUT is made by printing a series of colors and combining them with the relative "recipe", by necessity it is not possible to think of generating in this way a recipe for each possible color, but the recipe for the missing colors, that is, those that are not measured it is directly supplied by interpolation, by means of a series of algorithms that evaluate what it can be, using pairs of close “recipe” -measure values.

When the operator wants to print a certain color, the ICC profile indicates the recipe corresponding to it, even if the recipe is generated by interpolation and in this case it is a purely theoretical recipe and it is not known whether the result will actually be what you want. Often for various reasons the color actually printed differs, sometimes even substantially, with the color that indicates the recipe associated with it.

The known art teaches that given a color that you want to print, the system provides, thanks to the ICC profiles, the recipe corresponding to it, but once printing is set using that recipe, it is not at all obvious that the printed color is the one initially set. Indeed most of the time the result is very different from the initial one.

There are several profiling systems that also produce substantial differences in the printing results, but color management is one of the open problems of printing systems and none of the known systems solves the serious technical problem of being able to know, before printing, what the concrete result of the print will be and therefore you can know in advance what the final result will be.

The result of the print is, to date, a print that, although improved, always presents some differences with respect to the desired print.

Therefore, with traditional systems, including the more advanced ones, it is not possible to be sure that the print corresponds to the image designed and / or displayed on the screen.

The disadvantages that the state of the art presents are obvious. Printing is often very expensive, especially in industrial processes, but it is absolutely uneconomical that in order to see what the concrete result is, it is necessary to print proofs. Add to this the enormous waste of time and the fact that, by approximation, it is often necessary to make more prints with consequent multiplication of costs. The only effective way to be able to see what the printing result is, to date, consists in printing an image. Once the image is printed, it is compared with the desired result and the color settings are changed in order to be as close as possible to the desired result. This obviously determines a waste of materials, time and a considerable cost.

In essence, therefore, the main problem of the known art is linked to the fact of having printing systems in which the result that will be obtained once printing is not predictable with certainty. This problem is made even worse by the fact that often for technical and commercial needs it is necessary to have different graphics processing programs and different computers or CPUs communicate with different printers, all this obviously taking into account the difference in the media on which you will print.

The present invention solves the aforementioned technical problems by means of a method for managing color in a printing process which includes the following steps:

a) provide a recipe, or a preferred percentage of inks;

b) printing by means of a printing device a real color obtained by means of said recipe;

c) obtaining, by means of a measuring instrument, the real measure of said at least real color printed by said printing device;

d) associating the real measure of said real color to said recipe

e) preparing an ideal image comprising at least one ideal color generated by at least one recipe

f) to replace each ideal color of said image with the corresponding real color, for example by identifying the correspondence by comparison between real color and ideal color.

It is possible that the replacement of the ideal color with the real color, or the "transformation" of the image from ideal to real, occurs automatically, as defined above, or that the operator is asked to confirm, or that the operator can have an ideal image without colors and that can add colors, or color it, choosing from the only real colors available.

In this way, each ideal color, or initially chosen by the operator, is replaced in the drawing, or image or the like, with the corresponding real color, or with the color that will actually be printed by the printing device.

In practice, the method according to the present invention provides that the ideal color is the color that the graphic processing program, or the like, has in its memory as a color that should be printed following a precise recipe, ie percentage mixing of the inks. For the problems described above, however, the so-called ideal color almost never reflects the corresponding so-called real color, that is, the color that the printing device actually produces.

Using the above method, the color that is printed by the printing device following the associated recipe is measured, and the result of the measurement is used to replace the ideal color with the real color, which will then actually be printed following the recipe.

By repeating the above process it is possible to generate a true color palette, which includes only the colors actually printed by the printing device.

The method is applied to the specific overall printing system (i.e. printing machine, substrate and inks) to be used and to give the desired results it must be repeated every time any component of the printing system is changed, including any adjustment. that may change the printing conditions.

The invention object of the present invention therefore solves the drawbacks previously described since the display system of the image to be printed uses a series of colors, the information of which is contained in the palette descriptor, which includes only the colors that the specific printing system actually printed and which were measured after printing.

The solution in question envisages using only the colors printed by the printer and then measured, that is, only those for which there is certain proof that the printer is able to produce and not others.

No profiling or interpolation of colors is therefore used for the generation of the colors of the printing system, but only those colors that the printer has actually produced are used, i.e. the real colors for which it is possible to know the result a priori without the need to do further printing tests.

According to an advantageous characteristic of the present invention, while in the ICC profiles currently used the printing of the color to be obtained takes place through the calculation by interpolation of the "recipe" that should produce the color itself, in the present invention it takes place using the color recipe real actually printed more like the ideal color.

According to an advantageous embodiment, the method, object of the present invention, is carried out with the following steps:

1. a computer program or software produces the appropriate information, in the form of one or more files, to print an image containing a certain number of colored areas, hereinafter referred to as "palette". Said file (s) contains / es in particular color recipes. This software stores the information for the physical realization of the palette in the form that is usually used by a printing process, i.e. as a combination of density of the dyes (inks) used by the printer, the so-called “Recipe” that defines how each color contained in the palette has been produced;

2. using the recipe of each color present in the file, ie the combination of color density, the printer produces a series of colored areas, called patches, which make up the palette, the real colorimetric values of which are unknown a priori; 3. the colored areas of the palette, once printed, are measured with a measuring medium or instrument for measuring color, preferably the measuring medium can be a spectrophotometer, however, an RGB scanner and / or camera can also be used and / or similar color measurement tools.

4. each measure of the corresponding colored area of the palette is then associated with the recipe on the basis of which it was printed, essentially combining the real measure of the real color with the recipe that produced it, generating a file which in the rest of the description is called "descriptor of the palette ", which consists of a file that contains all the information on the real colors, i.e. produced by the printing process, i.e. both the recipe, already known before the palette printing process, and the measurement of the real color itself, known instead after printing.

When you want to print any image, an application program generates a new image called approximate or "proof ', corresponding in shape to the original image, but generated using the" palette descriptor "to replace the colorimetric value of each point of the original image the colorimetric value contained in the "palette descriptor" most similar to it and thus providing a "proof" image or an image corresponding to the actual print.

Basically, the method according to the present invention provides that a computer program replaces the ideal colors of an image with the real colors that will be obtained by printing the image by means of the printing device, by means of the method described above. The replacement of an ideal color with the real color is done in a preferred way by identifying the similarity of two colors. The evaluation of the similarity of two colors is a function defined by recognized standards such as eg. the Delta E of the CIE.

The approximate or "proof" image can then be printed, making sure that the colors it contains will be reproduced exactly by the printer, because each color of the approximated image has been obtained from the palette descriptor, created as a result of the measurement of the palette itself.

In practice, the original image is modified using only the colors that the printing process is able to produce, making the approximation based on the real colors produced by the printing process.

The system object of the present invention allows you to choose the color to be printed within a list of real colors that the printer has actually printed and that have been measured and reported in this list by combining them with their recipe.

Once you have obtained the color recipe in this way, therefore, you can be sure that the printer will reproduce that color.

In this way, the drawbacks of the known art related to the fact that, according to the current ICC technology, involves the use of interpolation for the creation of unmeasured colors, are easily overcome.

It is also possible to objectively measure the result obtained to evaluate whether the approximated image is satisfactory from the point of view of appearance, in the sense that the differences from the original are considered acceptable or not.

Since there is a pair of “recipe-measure” values in the palette descriptor, a proof image can be produced, while with the ICC profile the recipe is interpolated since it is not possible to know which color will actually be produced.

This is achieved by applying mathematical functions to the approximate and original image, which evaluate the color differences in numerical terms of perceptual difference.

It is therefore possible to obtain an overall assessment of similarity that objectively measures the goodness or otherwise of the transformation carried out for its printing.

Furthermore, using the recipe that is associated with each patch of the palette, it is possible to produce the information required by the printing process to reproduce the approximate image. For example, in the case of a screen printing process, the application software, using the associated recipe for each point of the approximated image, will produce the information necessary for the preparation of the screen printing screens needed for printing. In the profiling system according to the known art ICC, given a color to be printed, the system provides the recipe that allows you to create that color. This happens because in the ICC profile there is a phase of measuring the colors printed by the printer, as in our system, but once a certain number of colors has been measured, a 3D structure (CLUT) is created which contains both the recipes of the printed colors and those of colors not printed, but obtained through mathematical interpolation algorithms. The structure created, therefore, contains only part of real data, while many of them are only hypothetical.

It follows that a current CMS according to the known art allows you to obtain the recipe for printing a certain color from the ICC profile, but does not offer any guarantee that the color that will be printed will actually be the desired one. Furthermore, it is not possible to know a priori what difference may exist between the desired color and the printed color or to visualize which one it is.

The system object of the present invention, on the other hand, allows you to choose the color to be printed within a list of real colors that the printer has actually printed and that have been measured and reported in this list by combining them with their recipe.

Having chosen the color in this way, therefore, you can be sure that the printer will reproduce that color, according to the recipe associated with it.

Furthermore, according to the system object of the present invention it is possible to objectively measure the result obtained to evaluate whether the approximated image is satisfactory from the point of view of appearance, in the sense that the differences from the original are considered acceptable or not. This is achieved by applying mathematical functions to the approximate and original image, which evaluate the chromatic and perceptual differences in numerical terms.

It is therefore possible to obtain an overall assessment of similarity that objectively measures the goodness or otherwise of the transformation carried out for its printing.

Reduced to its essential structure and with reference to the figures of the attached drawings, a method for managing color in a printing system, according to the present invention, provides that the choice of the color to be printed, which is closest to that desired by the user, is carried out using as a parameter of choice the colors actually printed by the printer and measured, i.e. the user chooses the ideal colors, or those that ideally would like to see represented after the printing process, and the method and system of implementation of the method according to the present invention they provide the user with the result in terms of real colors, that is how the image or drawing or writing or the like will actually be after the printing process, and this without printing Γ image or drawing or writing or the like, but printing _ measuring a sheet of specimens, or patches, which specimens are measured according to the method described above and the measurement obtained is used lized for the generation of a real image, that is an image similar to the ideal image, but displayed, for example on the screen, by using only real colors, that is actually printable, which are substituted for the ideal colors.

The system foresees that, given a color to be printed, it is possible to choose the color closest to it, according to a perceptual meter, using a file, called the palette descriptor, which contains information only on the colors actually printed by the printer and measured. This information consists of each recipe combined with the measurement of the color corresponding to it actually printed.

The fundamental innovation of the present invention consists in the fact that the color management system is based on the colors actually printed by the printer which constitute the parameter of choice for the end user. The operator or user, when designing the image to be printed, can choose the colors from a list of colors consisting only of the colors actually printed by the printer and measured. Therefore the approximate image or real image, which reproduces the image to be printed or the ideal image, is identical to the image that will then be printed, being made up of the same real colors resulting from the printing process.

The method according to the present invention provides, especially in the case in which it is implemented by means of a CPU, or computer or the like, that for the generation of a file, the so-called palette descriptor, the following steps:

- prepare at least one recipe and / or composition, which substantially consists of percentages of dyes and / or inks;

printing at least one real color using said recipe;

- measure and / or acquire at least one colorimetric value or real measurement of the real color resulting from the printing of the corresponding recipe;

- associate the real measure of the corresponding real color to at least one recipe.

The method foresees that initially a series of recipes are printed, the real result of which is not known. The printing produces a series of patches, or areas colored with real colors, or with actually printed colors, each of which areas, corresponding to a specific recipe, will then be measured, being DOI said real measure combined with the corresponding recipe.

The data of the actual measurement and of the recipe are collected in a file, called "palette descriptor" which constitutes the parameter of choice that can be used for the formation of an approximate image (or "proof ') or of a real image, in which image real colors are replaced with real colors.

Advantageously, the list of real colors reproducible by the printer (so-called palette descriptor) consists of a file containing the information on said colors (or the "recipe" of each color combined with the measurement of the printed color) that allow the printing process to produce palette colors.

The system therefore allows not only to see on the screen the real color that the printer can reproduce, but above all to measure the differences between said color and the desired color, that is the ideal color. In fact, it is not certain that there is a coincidence between the two colors, as often happens according to the procedures of the known art.

In the ICC system, this coincidence is hypothetical, as the system provides the closest recipe without guaranteeing that that recipe will give exactly the desired result. In the system object of the invention, on the other hand, the closest color is immediately proposed for which the information is known that allows you to evaluate how much it approaches or moves away from the desired color.

Advantageously, said color information allows to measure the differences existing between the desired color and the color actually reproducible by the printer.

Advantageously, the aforementioned color information is used for the creation of an image, called "proof", which can be viewed on a monitor and consists of real colors, that is, actually printed by the printer and only by those.

The creation of this "proof" image that corresponds exactly to the image that can be printed allows you to evaluate what the "a priori" result is and to make measurements that can allow you to calculate and / or highlight the differences, not only between the single colors, but also between the desired image, that is the ideal image, and the printable image, that is the real image.

This allows the user to check different choices before physically proceeding with printing, perhaps changing some colors and replacing them with others or choosing the printing configuration that provides the best result, or closest to the ideal result.

The invention allows the operator to use a program containing all the information on the colors actually printed by the printer in order to be able to replace each ideal color of the original ideal image with these real colors and generate the final image, that is the real image corresponding to the one that will actually be printed.

In the method in question, the first phase is identical to that used to produce an ICC profile: a target is printed, obtained by combining the percentages of the inks in an algebraic way in order to produce a large number of combinations of inks and therefore to obtain a large number of different colors. For example, if the printing system had 4 inks and 6 print densities (0, 20, 40, 60, 80, 100%), such a Target would be made up of 1,296 colored cards. It is evident that the more the target colors are numerous and well distributed within the gamut of the printer, the better the profiling result will be, because the printer gamut will be better sampled.

According to an advantageous embodiment of the present invention, the target thus produced is measured with a spectrophotometer and the measurements thus obtained are evaluated to decide whether they can be used to create the palette descriptor or to produce a better target, i.e. that produces colors that are more uniformly distributed in the Gamut of the printer, evaluated in the CIELab color space. For this purpose, a specific software is used which calculates which colors are needed to achieve the desired degree of uniformity and which for each of the new colors derives a new recipe by interpolating between known values of recipe-measure pairs.

The software obtains, from the values measured in the CIE Lab color space, the gamut of the printer and divides it according to a 3D grid with a defined pitch. The percentage of inks needed to produce the equivalent color is calculated from the Lab value of each point (intersection) of the grid, using the information on “neighboring” colors. In fact, for each color measured there is a “recipe”, ie the percentages of the inks used. It is therefore a CIE Lab three-dimensional space interpolation procedure, which produces a new target whose colors should be uniformly distributed within the gamut of the printer according to the chosen grid.

The set of old and new recipes allows you to produce a new target, called Level 1. By printing this new target and measuring the resulting colors, it is subsequently evaluated whether the desired uniformity has been achieved or a further approximation phase is required. To evaluate how much the real measured values are uniformly distributed in the CIELab space, there are various mathematical methods, such as the measurement of the local density and the calculation of the standard deviation with respect to the average.

The Level 1 target is printed and measured with a spectrophotometer. If the measured values do not satisfy the criteria of being "uniformly distributed", they can still be used again to generate a new target (called Level 2) whose colors are more uniformly distributed in the CIE Lab color space. In practice this procedure tends to produce a target whose colors produce colors so well distributed in the printer's color space that it accurately describes its behavior. In summary, while in the ICC profile the table contains numerical values "invented" by Γ interpolation of the measured values, instead the method in question produces a table containing only measured and therefore true values.

According to this advantageous embodiment, it is therefore possible to produce a target consisting of colors distributed as uniformly as possible within the Gamut obtainable with the inks of the printing system in question. By printing this new target and measuring the resulting colors, it is evaluated if the desired uniformity has been achieved or if a further approximation phase is needed. The substantial difference between the present invention and the known art is that the method proposed by the present invention verifies the hypotheses made, by printing and measuring the assumed colors, as described above.

Advantageously, the information contained in the palette descriptor can be used in two ways:

- by a program created in such a way as to modify the original image, replacing each color with the most similar one obtained from the descriptor. In this way, an approximate image is produced that represents how the image will actually be printed;

- from a CMS that uses the descriptor as it would use the CLUT contained in the ICC profile, that is by calculating the recipe that should produce the required color by interpolating "close" values of measure-color / recipe pairs Advantageously the above method provides for the capture as many colors as possible, as the more colors are scanned the better the user's needs can be met. However, this does not mean that the acquired colors can also be reduced according to the specific printing needs.

The system provides for the existence of a file that contains the information necessary for the printer to print the colors. This file is updated with the RGB and / or CIE Lab and / or spectral values for the creation of the so-called palette descriptor (Fig. 1).

Advantageously, the color information file generated at the beginning of the process, taking into account the colors (T) available to the printer and the possible densities (D), allows the printing of a palette, having a known number of colors and the as much as possible.

The printed palette (Fig. 2) consists of a series of colored areas (the so-called tiles or patches or areas), eg. produced with T dyes and D densities.

The dimensions of the tiles must be compatible with the characteristics of the instrument used to measure the colorimetric value. They can also be very small (for example lxl mm) in order to concentrate the largest possible number of colors on a small surface, making color acquisition faster and reducing scanning times to a minimum.

In this case, an RGB scanner or a spectrometric scanner will be used which, due to its peculiar acquisition characteristics, allows to acquire even small areas with maximum precision and in a shorter time.

The result of the acquisition is a file that contains the colorimetric measurement of each real color produced combined with the respective recipe.

This result is added to the initial result of the color recipe so that at the end of the process a file (so-called palette descriptor) is obtained which contains, for each color, both its measure and its composition or recipe, data that can be used for various purposes, but which essentially allow you to know the result already in the preparation phase of the print data and therefore before printing.

It is clear that such a system makes it unnecessary to carry out test prints and then adjust the recipes so that the print is as similar as possible to the desired one, since thanks to the present invention the procedure is completely reversed.

Advantageously, the palette descriptor thus created can be used by a program which allows the designer to use this palette for the production of test images. The program is designed in such a way as to modify the original or ideal image, replacing each color with the most similar one obtained from the palette descriptor. In this way, an approximate or real image is produced that represents how the image will actually be printed.

Advantageously, the system of the present invention can be applied to any printing process.

Advantageously, it is also possible to measure the differences between the original image and the approximate image that represents what will actually be printed.

Further characteristics are the subject of the attached claims and / or sub-claims.

The advantages and characteristics of the present invention will be better understood by every person skilled in the art from the above description and with the help of the attached drawings given by way of example and not to be considered as limiting, in which:

- Fig. 1 shows an example of the content of the file, also called in the following description "palette descriptor" of the colors, reduced in size for simplicity of representation and which in the lower right shows some measures of the colored areas of the palette measured after the print. The palette descriptor contains both the color recipes, known a priori, and the spectral or CIELab measurement of the colors, carried out after printing the color palette;

- Fig. 2 shows, by way of example, the printing of a “palette”, that is the series of printable colors. However, black and white printing makes it difficult to understand the different color variations.

Claims (31)

CLAIMS 1. A method for managing color in a printing process characterized by the fact that it includes the following steps: a) define at least one recipe, or at least a preferred percentage of inks; b) printing by means of a printing device a real color obtained by means of said at least one recipe; c) measuring, by means of a suitable measuring means, the real measure of said at least one real color printed by said printing device; d) associating the real measure of said real color to said recipe e) replace each ideal color of an ideal image to be printed with the corresponding real color. 2. Method according to claim 1 characterized in that it provides for the generation of a so-called descriptor of a palette of real colors and corresponding recipes and measures, generated by repeating the method steps from a) to d) of claim 1. 3. Method according to one or more of claims 1 to 2 characterized in that said palette comprises a certain number of colored areas. 4. Method according to one or more of claims 1 to 3 characterized in that said palette is generated by a computer program or software loaded or running on at least one CPU or computer or electronic processor. 5. Method according to one or more of claims 1 to 4 characterized in that said software or program stores the combination of density of the dyes (inks) used by the printer, or the said recipe which defines how each color contained in the palette that has been product. 6. Method according to one or more of claims 1 to 5 characterized in that said print of said real colors of said palette is produced using the recipe of each color present in the file, i.e. the combination of density of the colors, i.e. the printer produces a series of colored areas, called patches, which make up the palette, the real colorimetric values of which are unknown a priori. Method according to one or more of claims 1 to 6 characterized in that the printed colored areas of the palette, called patches, are measured with a measuring means or instrument for measuring color, preferably spectrophotometer and / or an RGB scanner and / or RGB camera and / or spectrometer scanner and / or similar color measurement tools. 8. Method according to one or more of claims 1 to 7 characterized in that said measurement of the corresponding colored area of the palette is associated with the recipe on the basis of which it was printed, essentially associating the actual measurement of the real color to the recipe that has it generated. Method according to one or more of claims 1 to 8 characterized in that said software or program generates a file called "palette descriptor", said palette descriptor consisting of a file containing information on the actual colors associated with the corresponding recipes. 10. Method according to one or more of claims 1 to 9 characterized by the fact that the choice of the color of the ideal image, or image to be printed, is carried out using as a choice parameter only the colors actually printed by the printer and measured, or the only real colors. Method according to one or more of claims 1 to 10 characterized in that, for the generation of a "file", said palette descriptor, comprises the following steps: - prepare at least one recipe and / or composition, which basically consists of percentages of dyes and / or inks - print at least one real color using said recipe; - measure and / or acquire at least one colorimetric value or real measurement of the real color resulting from the printing of the corresponding recipe; - associate the real measure of the corresponding real color to at least one recipe. 12. Method according to one or more of claims 1 to 11 characterized in that said information contained in said palette descriptor is the information in percentages of colors (T) and density (D) possibly printable by the printer, to which they are associated with the RGB and / or CIE Lab and / or spectral values relating to the real colors actually printed with said information. 13. Method according to one or more of claims 1 to 12 characterized in that said color information contained in the so-called palette descriptor, are used to create a real image, called "proof" that can be viewed on a monitor and consists of the real colors actually printed and measured by the printer. 14. Method according to one or more of claims 1 to 13 characterized by the fact that said real image or "proof" presents only and only the real colors, actually printed by the printing device. 15. Method according to one or more of claims 1 to 14 characterized by the fact that said real or "proof" image is measurable and comparable with the ideal image 16. Method according to one or more of claims 1 to 15 characterized in that the comparison between said real or "proof" image and said ideal image provides the difference between said two images and / or between the individual points of said two ideal images it's real. 17. Method according to one or more of claims 1 to 16 characterized in that said replacement of the ideal color of said ideal image with the corresponding real color is carried out on the basis of a criterion of similarity of two colors, said similarity being a function defined by known and recognized standards such as a Delta E of the CIE. 18. Method according to one or more of claims 1 to 17 characterized in that said method is implemented or implemented by means of an electronic computer program, which carries out the following steps: - Initially, an application software produces the appropriate information, in the form of one or more fìles, so that an image containing a certain number of colored areas (hereinafter referred to as "palette") is printed. Said file (s) contains / es in particular color recipes. This software stores the information for the physical realization of the palette in the form that is usually used by a printing process, that is, as a combination of density of the dyes (inks) used by the printer (the so-called "recipe" which defines how each color is composed of the palette). - Using the recipes present in the file (i.e. the combination of color density) the printer produces a series of colored areas, called patches, (so-called palette) whose colorimetric values are unknown a priori. - The colored areas of the palette, once printed, are measured with a suitable instrument for measuring the color - The measurement of each colored area of the palette is then associated with the recipe on the basis of which it was printed, generating a file called "palette descriptor", which consists of a file that contains both the recipe of the color actually printed, already known before the printing process of the palette, and the value of the measurement, carried out after printing. 19. Method according to one or more of claims 1 to 18 characterized in that it comprises a program which, given an image to be printed or an ideal image, produces a new image, called approximate or real or "proof", using the "descriptor of the palette "and replacing the colorimetric value of each point of the original image with the colorimetric value contained in the" palette descriptor "most similar to it and thus providing a real or" proof "image corresponding to the real print. 20. Method according to one or more of claims 1 to 19 characterized in that it also provides for the following steps: - generate a so-called target or a palette of printable colors - said target or palette is measured with a suitable instrument - said measurements of said target are evaluated in terms of uniform distribution in the CIELab space and alternatively: either they are used to create the said palette descriptor, or they are reused to produce a new target, having colors that are more uniformly distributed in the Gamut of the printer , preferably evaluated in the CIELab color space. 21. Method according to claim 20 characterized in that said new target is generated to achieve the desired degree of uniformity and that for each of the new colors it derives a new recipe using known values of recipe-measure pairs, or generates new colors calculated starting from from measurement data of real color associated with the corresponding recipe. Method according to one or more of claims 20 or 21 characterized in that it provides for the following steps: - obtain the printer gamut from the values measured in the CIE Lab color space - subdivide said space according to a 3D grid with a defined pitch - calculate the percentage of inks needed to produce the color equivalent to the Lab value of each point (intersection) of the grid using information on real "neighboring" colors 23. Method according to one or more of claims 20 to 22 characterized in that it provides for the following steps: - print the new target obtained with these recipes - measure the resulting colors of the new target with a suitable instrument - evaluate, with any suitable algorithm, if the desired uniformity has been achieved or if a further approximation phase is needed 24. Method according to one or more of claims 20 to 23 characterized in that it provides for the following step: repeating one or more of the steps of claims 20 to 23. 25. Method according to one or more of the preceding claims, characterized in that one or more of the steps relating thereto can be carried out by means of a computer program. 26. Computer program, comprising computer codes, developed to carry out all the steps of the method according to one or more of the preceding claims when said program is executed from a computer. 27. Computer program, comprising computer codes, developed to carry out all the steps of the method according to one or more of the preceding claims incorporated in a computer readable medium, and or loaded into the memory of a computer or CPU or the like. 28. System for managing color in a printing process comprising: - at least one display means of at least one ideal image comprising at least one ideal color, such as for example a video or monitor or the like - at least one printing device, such as a printer, a screen printing machine, or the like - at least one means for detecting at least one color parameter, such as for example a spectrophotometer and / or an RGB scanner and / or RGB camera and / or spectrometric scanner and / or similar color measuring instruments characterized in that it comprises the following method steps: - providing a so-called recipe consisting of at least a preferred percentage of color mixing - printing by means of said printing device at least one specimen or real color of said at least one real color corresponding to said recipe - detecting by means of the said measuring device the at least one parameter of the said at least one real color - associate said parameter or measure of said real color to the corresponding recipe - view, through the display medium, the real color corresponding to the parameter of the corresponding recipe - replace each ideal color of the ideal image with a corresponding or similar real color, generating a real image System according to claim 28 characterized in that it comprises one or more of the method steps according to one or more of claims 1 to 27. 30. Method according to one or more of claims 1 to 27 characterized in that it is applied to the specific printing system to be used and must be repeated every time any component of the printing system and / or any adjustment is changed that may change the printing conditions. 31. System according to claim 28 and / or 29 characterized in that it is applied to the specific printing system to be used and must be repeated every time any component of the printing system and / or any adjustment that may be change the print conditions.