DE102006040609A1 - Method and arrangement for determining a color assignment of source colors and target colors - Google Patents

Abstract

The invention relates to a method and a device for determining a color assignment of source colors and target colors, in which a plurality of mutually different source colors are selected. At least one output image is output with a representation of the selected source colors. The color value of the output representation of each source color is determined as the target color. Using the selected source colors and the target color determined for each source color, a global mapping function is determined.

Description

The The invention relates to a method and an arrangement, by which a Source color of a source color space is a target color of a target color space and / or a target color of the target color space, a source color of a source color space can be assigned in a simple way.

With The term "colorants" are used in the sense the invention and throughout the following description all Substances designated for an output of colors can be used. Depending on the output device, these are Different substances. In conventional printing systems, such as flat, Gravure, flexo, flexo and screen printing, these colorants are also referred to as printing inks. These inks are for playback standardized from multicolor images. For digital printing systems, based on an electrophotographic imaging principle the colorants generally as a toner, in particular because of their Consistency as dry toner or liquid toner. at digital printing systems based on an ink-jet imaging principle the colorants referred to as inks. Colorants for one Printing process thus include inks, toners and inks and blends multiple inks, multiple toners and multiple inks.

Further output devices for image output using colorants are screens, as colorants according to technology fluorescent dyes (CRT), Color filter, colored light emitting radiation sources, in particular LED's, phosphors, which are excited by plasma discharges, etc. use. in the Difference to the term "color" marks the Term "colorant" means a substance.

It is known to prepare a colorant mixture with a desired mixed color from a plurality of different colored starting colorants. The mixed color of the colorant mixture is a desired target color in the target color space. For example, colorant mixtures based on toners with special mixed colors are marketed by the applicant under the trade name Océ CustomTone. The Océ CustomTone colors are in the document "Digital Printing Technology and Printing Technology of Océ Printing Systems", 9th edition, February 2005, ISBN-3-00-001019-X , described in chapter 3. The illustrations for the Océ CustomTone inks as well as for color printing in this document are hereby incorporated by reference into the present specification.

Around For example, produce suitable colorant mixtures for a printing process to be able to is a possible one Approach, a color recipe with proportions of starting colorant for manufacturing to determine the colorant mixture individually. To get out of these known Color recipes further color recipes for the preparation of colorant mixtures derive further mixed colors, approaches have been tested in which the available standing starting colorant in concentration series with different Proportions of the starting colorants in different colorant mixtures and / or in layer thickness rows with high accuracy on different Printed substrates under optimal well-defined conditions have been.

From The printed colors become the absorption and scattering coefficients separately for each starting colorant contained in the respective colorant mixture certainly. However, this requires a precise knowledge of the behavior the respective starting colorant and the colorant mixture in a variation of an output condition, in particular of the printing substrate. Further, an accurate knowledge of the layer thickness of the expressed expression required. Exact universal Forecasts are not with these described procedures reachable. To use this approach, a prediction of a expected mixed color of a colorant mixture during printing to be able to meet have to complex calculations assuming theoretical ideal ratios, especially of infinite layer thicknesses. Already by these assumptions is an accurate prediction of the actual Mixed color of the colorant mixture not possible. The starting colorants for producing colorant mixtures with different from each other Mixed colors have suitable starting colors and serve as base colorant with known basic colors. Usually are for generating colorant mixtures 4 to 20 basic colorant to disposal, of which in a colorant mixture usually shares of two, three or four primary colorants are used.

Furthermore, color management systems are known, by which an assignment of a color specified in a color system to a device-specified color of an input and / or output system for specific input and / or output conditions is determined by an allocation table. Here are for output devices such as printers under special output conditions using several hundred, preferably at least 1000, selected colors in a color space assigned source or target colors determined and entered in the color assignment table. For input devices and monitors are several hundred reference colors common. The selected colors are evenly distributed over a color space relevant area of a color space. If an input and / or output condition is changed, a new color assignment table must be created by preferably repeatedly determining the associated source or destination colors using the same number of selected colors. With the help of a color management system is thus generally a mapping of a gerätespezifi's color description and the color look possible. The color appearance, ie the color produced, can be described by specifying the color in a standardized color system such as CIELAB, CIELUV, CIEXYZ, sRGB or color fans such as Pantone ^™ and HKS color tables.

With Help of a color management system can be for individual at the color processing involved devices, such as e.g. Scanners, monitors and color printers, one device profile each to create a uniform representation of the same colors. Standards for the format of these device profiles are, for example, by the International Color Consortium (ICC) been issued.

For example becomes the color management for the output of color representations on a color printer a large number printed out different test colors, which are also used as test fields be designated. The actual colors in the target color space of the printed one Test colors are then determined and the corresponding source color in the source color space assigned. This approach will be for local customization Sectional conversion tables identified for the implementation the color data to be output are used. Between those for the test points determined values of the conversion tables are used to assign more Values interpolated assignments determined. Both generating such Conversion tables as well as the inclusion of these conversion tables as a color profile in a printing process is expensive and at least in the color range between the determined test points inaccurate. A change of basic parameters, like a change the substrate to be printed, the layer thickness of the generated print images as well as the measurement conditions, requires a complete re-capture of the color profile.

task The invention is a method and an arrangement for determining specify a color mapping of source colors and destination colors the both a color management and the determination of a suitable Composition of starting toners to a mixed toner to simple Way possible is.

These Task is through the objects with features of independent claims solved. Advantageous developments of the invention are specified in the dependent claims.

Of the The invention is based on the recognition, a global mapping function using some test points to determine through which each source color of a source color space, a target color of a target color space, as well as each Target color of the target color space at least one source color of the source color space is assignable. To determine this mapping function are only relatively few test points are needed, which serve as support points serve this mapping function. With the help of further subsequently recorded reference points can the precision the imaging function can be further improved. With the help of this Picture function can Also, mappings are generated in color space areas that are not in the from the support points covered area. With the help of this mapping function is a uniform global mapping possibility between the color values the target and the source color space possible. This mapping function let yourself both for so-called color management as well as finding suitable mixing ratios of starting toners use, which when mixed a mixed toner with a predetermined Create target color.

When changing a parameter that is essential for the color representation, such as, for example, when using a different carrier material when outputting a printed image, a few new interpolation points are created in order to generate a new mapping function that takes into account the changed parameter or if there is a choice between the original parameter and the new parameter is possible. With the help of the mapping function, color values can thus be converted into a printer-specific color formulation by any color system, such as CIELAB, CIELUV, CIEXYZ, sRGB, a Pantone ^™ color fan or an HKS color table. In general, the imaging function can be used to determine starting colors and starting colorants for producing desired printing inks, desired RGB values, desired ink colors and desired toner colors.

The determined global mapping function serves as global conversion function of colors. The mapping function is based on a few reference data necessary to determine the mapping function. Such a mapping function can be used for any conversion of source colors into target colors as well as target colors in source colors, whereby colors of any source color spaces and any target color trees can be transformed.

The described procedure for determining and using the mapping function is for various types of color mixtures, especially for additive, subtractive and / or autotypical color mixtures, applicable. Further is the consideration additional parameters possible, mapping the source colors to the target colors as well as the target colors affect the source colors and / or their representation. These Parameters can are also summarized as parameter variants, where it is in the parameters around continuous or discontinuous parameters can act.

With Help of the mapping function is also a reversibility of the mapping possible from source colors to target colors for a given target color, a source color and / or composition of Source color can be determined.

To a later one Time can additional reference points be set to improve the mapping function, wherein then a new improved mapping function is detected, which all support points considered. This extra reference points can then be provided in particular in areas of color spaces in which with the help of the already determined mapping function one not sufficiently accurate color conversion takes place. This becomes a learning System provided by the adaptive refinement of Accuracy of the mapping function is possible. With the help of the determined Imaging function is also an extrapolation, in particular enlarged color ranges and other output parameters possible.

The Number of minimum required test points or points preferably results from the number of free function parameters a suitable mapping function and is considerably lower than in color management using mapping tables. For mixed toners out of a total of seven possible starting colors or seven output toners with different output colors 50 to 200 test points have proved to be favorable. Preferably can 80 to 120 test points are used. The target color space is included preferably that represented by the printable inks of a printer limited color space. The printouts corresponding to the test points are measured in a known manner, with color values preferably as CIELAB color values. As source data space can be a through an RGB, SRGB, CMYK, HKS, CIELAB, CIELUV, CIEXYZ color system or a suitable color fan defined color space can be used.

Out The procedure described results in a number of advantages. In particular, only one is used to determine the mapping function low number of test points or interpolation points required. For determining a mapping function for color formulation with four to seven Source colors lead Colorant mixtures with mutually different mixed colors at ≥ 25 test points to good results, which differs from known approaches a large Time and cost advantage results. A meaningful color recipe is already possible with imaging functions, with the help of less were determined as ten test points. The concrete quantitative Proportions of the starting colorants on the colorant mixture and the source colors the test points are freely selectable and must do not lie on a fixed grid. In the described procedure is a high accuracy in determining the proportions of the starting colorants possible on a suitable colorant mixture.

Of the Scope of the invention for color formulation includes all Image forming processes, in particular flat, gravure, high flexo, flexo, Screen printing and digital imaging techniques, such as electrographic and inkjet imaging process. All printing and imaging processes can used in both a printing and a copying process become. The invention may be particularly advantageous in connection be used with electrophotographic printers and copiers.

It is achieved by the method having the features of patent claim 1 that a source color can be assigned to each desired target color with the aid of the determined global mapping function. Thus, with this method, color management can be easily performed when the target color to be outputted is determined to be a source color required to produce that target color. The desired target color is preferably predetermined by an application program. Then, with the aid of the mapping function, a source color assigned to the target color to be output is determined, and corresponding color data (for example print data) are output for generating the determined source color. With the help of this color data, an output image is then generated with the desired target color to be output. For example, the target color can be specified by the CIELAB color model and the source color by the available CMYK colors of an output device. The mapping function may comprise a mathematical function, preferably at least one nth order polynomial and / or one artificial neural network (KNN).

One Target color space is in particular by the outputting of representations of target colors available limited output colors. To provide a color management system, a source color space may be provided limited to the target color space and / or adapted to the target color space. To determine the Mapping function should have at least three different source colors, preferably at least 25 different source colors as test points or interpolation points selected be over the available Color range or over the entire available standing color space are distributed. The distribution of the test points over the Color range or over the color space is preferably uniform, with a uniform distribution not the identical distance of the support points in the color space to each other requires, but only for determining a suitable mapping function over the entire color space a common one represents advantageous selection. With further source colors as test points the accuracy of the imaging function can be improved. The Imaging function can be used for color management for input and output devices especially for a printer or copier, preferably the colors cyan (C), Magenta (M), yellow (Y) and black (K) as primary colors.

One such printer or copier is in particular an electrographic, preferably an electrophotographic, printer or copier. A Imaging function and / or a color profile is preferred dependent on a substrate to be printed determined.

One Another application of the method according to claim 1 is a Color recipe for any image forming method, in particular flat, deep, high, Flexo, screen printing and digital imaging, such as electrographic and inkjet imaging processes. All printing and imaging methods can used in both a printing and a copying process become. The invention may be particularly advantageous in connection be used with electrophotographic printers and copiers. It is by the color formulation a mixing ratio of to be produced ink from given starting colors to a predetermined target color can be determined. The source color is preferably by a mixing ratio specified by starting colorants. Furthermore, by the Method according to Claim 1 with the aid of the determined imaging function the color components of a pixel to be output by a display unit a target color in the RGB color space be easily determined, with the source color by the RGB color components the RGB colorant is specified.

One Second aspect of the invention relates to a device for determining a color mapping of source colors and destination colors with the features of claim 14. With such a device can be achieve the same advantages as with the aid of the method according to claim 1.

One Third aspect of the invention relates to a method for determining an assignment of the mixed color of a colorant mixture and the Proportion of at least two starting colorants on the colorant mixture. There are several colorant mixtures produced, preferably each contain proportions of several starting colorant. A first Initial colorant has a first source color and a second Starting colorant has a second source color. By different Proportions of the respective starting colorants on the colorant mixture Colorant mixtures can be produced with one mixed color each. There are several mutually different colorant mixtures produced by different proportions of the starting colorant. Further For each test print is generated with a colorant mixture. The Mixed color of each colorant mixture is determined by determining the color values the test printouts. Using the proportions of the starting colorants in the mutually different colorant mixtures and to each mixed color mixture is a global Mapping function detected.

Thereby is achieved by using the mapping function to a desired predetermined mixed color the proportions of the generation of this mixed color required starting colorant determined in a simple manner can be. In particular, at least one suitable color recipe for producing a Produces colorant mixture, which has the predetermined mixed color. For more than two starting colorants, for each of these with the starting colorants potential Starting colorant combinations or for a part of the possible Starting colorant combinations the proportions of the starting colorants for each a colorant mixture or for each of these colorant mixtures will be determined a color recipe, whose mixed color is closest to the target color or matches the target color.

Furthermore, the colorant mixture may contain only one starting colorant, in particular for detecting the imaging function. The colorant mixture is preferably a mixed toner or a toner Schung, wherein the output colorants are Ausgangsstoner. Additionally or alternatively, the starting colorant and the colorant mixture may comprise liquid colorants, in particular printing inks, printing inks or liquid toners.

One Fourth aspect of the invention relates to a device for detecting an assignment of the mixed color of a colorant mixture and the Proportion of at least two starting colorants in the colorant mixture. A first starting colorant has a first starting color and a second source colorant has a second source color. There can be more Starting colorant can be provided with other output colors. With the help of the starting colorants are by different proportions the respective starting colorant on the colorant mixture from each other different colorant mixtures, each with a mixed color producible. There are first means for generating different from each other Colorant mixtures provided. Further, an image forming unit for generating at least one test expression each time Colorant mixture provided. The device has second means for determining the color value of the test printouts by which the Mixed color of the respective ones used to generate the test expression Colorant mixture is determined. Furthermore, third means for Determine a global mapping function using the proportions the starting colorant in the mutually different colorant mixtures provided on the mixed color determined for each colorant mixture.

With Help this device according to the fourth Aspect of the invention can achieve the same advantages as with the method according to the third Aspect of the invention.

One fifth Aspect of the invention relates to a method and a sixth aspect a device for determining the proportions of a first starting colorant agent and at least one second source colorant for producing a Colorant mixture. In this case, the proportion of the first starting colorant and the proportion of the second source colorant for generating a desired predetermined mixed color using a global mapping function determined. Thereby can in a simple way suitable color recipes to provide of colorant mixtures, in particular of mixed toners and printing inks, with desired Mixed colors are determined.

The Invention can be used advantageously in electrographic printing or copying machines their recording method for image formation in particular on the electrophotographic, magnetographic or ionographic Based recording principle. Further, the printing or copying machines may be a recording method use for image generation, in which an image recording medium directly or indirectly electrically driven pointwise. The invention however, is not limited to such electrographic printing or copying machines.

To the better understanding The present invention will be hereinafter referred to in the drawings preferred embodiments Referred to, described by specific terminology are. It should be noted, however, that the scope of protection of This invention should not be limited, since such changes and further modifications to the devices shown and / or the described method and such other applications the invention, as they are shown therein, as usual current or future Expertise of a competent Be considered professional.

The Figures show exemplary embodiments of the invention, namely:

1 a diagram with a color space which can be generated with the aid of three output toners;

2 the schematic representation of an artificial neural network for determining the proportions of Ausgangstonern on a mixed toner for generating a predetermined mixed color;

3 a flowchart for determining a mapping function using an artificial neural network according to a first embodiment;

4 a flow chart for determining a mapping function using an artificial neural network according to a second embodiment; and

5 a flowchart for determining the toner portions of Ausgangstonern for generating a suitable for displaying a desired mixed color mixed toner.

In 1 is a diagram showing the representation of a color space. The color values encompassed by this color space can be generated with the aid of a first output toner (toner 1), a second output toner (toner 2) and a third output toner (toner 3).

By different proportions of the toner 1 and the toner 2 in mixed toners, which contain only toner particles of the toner 1 and toner particles of the toner 2, mixed colors are generated on the graph shown with the help of a solid line 10 between the toner 1 and the toner 2 are arranged. In the 1 shown two-dimensional representation of the color space is a plan view of the three-dimensional Lab color space, which arranged on the X-axis, the red-green portion a * and on the Y-axis of the yellow-blue component b *. An axis with the brightness curve L * runs vertically through this XY plane in the direction of a Z-axis, not shown.

With the aid of a mixed toner produced from proportions of the toner 2 and the toner 3, mixed colors can be produced on the mixed toner, depending on the proportion of the toner 2 and the toner 3, which are in the Lab color space on the toner connecting the toner 2 and the toner 3 as a dashed line 12 are arranged. With the aid of a mixed toner produced from portions of the toner 1 and portions of the toner 3, mixed colors can be produced in the lab color space on the graph connecting the toner 1 and the toner 3 as a dashed line 14 are arranged. The between the graphs 10 . 12 . 14 spanned surface bounds the color space, which includes the colors that can be generated by means of different proportions of the toner 1, the toner 2 and the toner 3 in the mixed toner. By using the mixed toner in a raster image, further color tones can be generated, which lie outside the displayed color space.

If a mixed toner with one by the reference numeral 16 Shares of the toner 1, the toner 2 and the toner 3 in the mixed toner are required for the exact color reproduction. If only the toner 1 and the toner 2 are to be used to produce the mixed color, that is the color value of the mixed color 16 the next coming mixed color by the with the reference numeral 18 on the graph 10 marked mixed color. The mixed color which can be produced with the aid of toners 1 and 2 18 comes the desired mixed color 16 the next. It can be checked if the deviation between the color value of the mixed color 16 and the color value of the mixed color 18 for a representation of the desired mixed color 16 acceptable or not. This can be the color difference between the mixed color 18 and the mixed color 16 be determined and compared with a permissible limit. If the determined color difference is below the permissible limit value, ie within an acceptable tolerance range, then the mixed color 18 to display the desired preset target color 16 be used. The dependency of the mixed color on the proportions of the toners 1 to 3 and thus the position of the mixed color in the color space can be described according to the invention by means of a mapping function, which is described below in connection with FIGS 3 to 5 will be explained in more detail. This mapping function may preferably comprise an artificial neural network (ANN), at least one n-th order polynomial and / or other suitable functions which have been determined by non-linear iterative methods.

With Help of the determined mapping function determines a search algorithm also a relationship each of two output toners of one of these two output toners existing mixed toner, which has a mixed color whose visual Impression of the desired Target color closest comes.

How out 1 As can be seen, the vast majority of possible mixed colors to be produced are not on the graph 10 . 12 . 14 which connect the individual output colors of the three toners 1 to 3. The desired mixed color 16 However, with the help of a mixed toner with proportions of the toner 1, with proportions of the toner 2 and with portions of the toner 3 can be reproduced exactly.

at other embodiments can but also mixed toners with proportions of more than three starting toners be generated. Is the desired mixed color to be dispensed, i. the target color or target color, in the through the available and usable source toner color space, this target color can exactly with the help of an image forming apparatus when using the Mixed toner with the corresponding proportions of Ausgangstonern on a carrier material be reproduced.

In 2 An artificial neural network is shown, which has as input the proportions of n-output toner of a mixed toner and as output variables the quantities L *, a * and b * necessary for defining a color value in the CIELAB color space. The artificial neural network has suitable functions f1, f2, f3, by which output quantities from given input variables and input variables from given output variables are generated. The nodes of the artificial neural network formed by these functions f1, f2, f3 are also referred to as hidden layers. The artificial neural Network are supplied portions of each toner on a mixed toner as input variables and the color value measured by means of a test print with the respective mixed toner as an output variable. By determining a transition function f1, f2, f3 with free parameters with these input and output variables for each node, the artificial neural network is trained. Both the proportions of the respective toners 1 to n on a mixed toner and the color values generated with the aid of the mixed toner are supplied to the artificial neural network in a learning process in order to determine suitable transition functions and parameters. The individual toners 1 to n may have proportions of the mixed toner ranging from 0% to 100%.

A possible Mapping rule for assigning the color components to color values can be through a feed-forward back propagation Neuronal Network, where the number of free parameters by the number of neurons in the hidden layer is determined. As a number of free parameter, i. of the neurons, has a number in the range of 0.5 times the number of output toner to three times the number of output toner as cheap proved.

With Help the for selected Mixed toner color values of the printed images is in a non-linear iterative procedures through the artificial neural network defined equation system, which is used to describe the whole by any mixed colors from the starting toners toner 1 to n producible color space is used. To determine the mapping function with the help of artificial neural network have at least 25 to 30 test points spread over the color space that can be generated with the aid of the output toners has proved favorable, being for each of these test points is a mixed toner with specified proportions of at least two of the available output toner toners 1 until toner n is produced. The test points serve as bases for determining the mapping function. With each of these mixed toner then an expression is generated. The color value of the color reproduction the term is used for determined each mixed toner. As already described, it determines the artificial one neural network using these test points an imaging function between the proportions of the starting toner on the mixed toner and the with Help of the mixed toner generated color value. This can be a mapping function with relatively few test points and thus with relatively few test printouts be determined, with whose help assignments over the entire representable Color space can be determined.

alternative or additionally to the artificial neural network can other suitable non-linear iterative methods for determining the mapping function are used.

In 3 a flowchart for determining a suitable artificial neural network is shown. The flowchart is started in step S10. Subsequently, who determines the appropriate test points in step S12. In color management, these test points may be color values in a color space and, when determining a suitable colorant formulation for producing a mixed toner having a desired color of mixing, color portions of the toner toners 1 to toners n on a mixed toner.

Subsequently, will in step S14, a color representation of each set in step S12 Test points issued. Subsequently, in step S16, the actual Color values of the test points determined. Then, in step S18, the Structure of a suitable artificial neural network. In particular, the number the node or neurons set. This number of nodes can range from factor 0.5 times starting colors to factor three times starting colors lie. The starting colors in color management are in particular the with the help of the used printer or Copier's dispensable basic colors Cyan (C), Magenta (M) and Yellow (Y) or cyan (C), magenta (M), yellow (Y) and black (K). The starting colors in determining a suitable color formula for making a desired Mixed color are the source colors of the available source toners used to create the Making the mixed toner are available.

Then done in step S20 a non-linear optimization of the free parameters of the artificial neural network, so over the whole with the help of a printer or other output device representable Color space a suitable mapping function is provided. Subsequently the process in step S24 is ended.

In 4 FIG. 3 shows a flowchart for determining a suitable neural network according to a second embodiment. The process is started in step S30. Subsequently, in the same manner as in step S12 3 set suitable test points. Subsequently, in step S34, prints corresponding to the test points are generated. In step S36, the color values of the prints are subsequently determined and assigned to the specified test points.

Subsequently, in step S38, a part of the defined test points with the determined associated color values is selected. The selected test points are preferably selected such that they evenly cover the possible color space of the producible mixed colors or the printer. In step S40, the structure of a suitable artificial neural network is then determined as described in connection with step S18 3 has already been explained. In step S42, a nonlinear optimization of the free parameters of the artificial neural network takes place. In step S44, the suitability of the mapping function determined by the determined neural network is then checked by means of at least part of the test points not selected in step S38. In step S46, it is then checked whether in the check in step S44 there are impermissibly large deviations between the color values determined with the aid of the mapping function for the test points and the actually determined color values. Deviations suggest that the artificial neural network is over-adjusted. If this is the case, the sequence proceeds to step S40, wherein another structure of the artificial neural network, in particular with fewer parameters or fewer neurons, is determined. The process of steps S40 to S46 is repeated until it is determined in step S46 that the artificial neural network is not over-adjusted. Subsequently, the process in step S48 is completed.

In 5 Fig. 3 illustrates a process for selecting a suitable toner combination to produce a desired blend color. The process is started in step S50. Subsequently, a mixed color to be generated is determined in step S52. Subsequently, in step S54, a first possible toner combination of available output toners is determined. The starting toners preferably each have a different starting color from each other and can be used as a base toner for producing mixed toners having a desired color.

Stand For example, three output toner Toner 1 to 3 are available itself from these Ausgangsstonern four toner combinations, namely a first toner combination of the toner 1 and the toner 2, a second Toner combination of the toner 2 and the toner 3, a third toner combination from the toner 1 and the toner 3 and a fourth toner combination from the toner 1, the toner 2 and the toner 3. For the number of possible Toner combinations is the quantitative proportion of the respective starting toner not crucial to a mixed toner. The toner combination gives only the starting toner contained in a mixed toner per se and not their quantitative share. Thus, in step S54 only a first possible Toner combination of the possible Toner combinations defined or selected.

in the Step S56 will then be a suitable mixing ratio of the starting toners fixed first toner combination using the neural network determined. By the mixing ratio a mixed toner is specified that corresponds to the specified Target mixed color or one of these target mixed color close to producible Has mixed color. In step S58 it is then checked if there is another toner combination with the available Output toner can be generated. If that is the case, then in the Step S59 set the further toner combination and the step S56 for repeated this more toner combination, creating for this Another toner combination in turn a suitable mixing ratio of Output toner is determined to produce a mixed toner.

Of the Sequence of steps S56, S58, S59 is repeated until in step S58 it is determined that with the aid of the available output toner no further toner combination possible is and therefore for every possible one Toner combination a suitable mixing ratio has been determined. If this is the case, then in step S60 a to Generating the mixed color selected suitable toner combination. At this Selection will be in particular a toner combination with possible selected little output toners, wherein also the deviation of the producible mixed color to the given one Target mix color, the number of blend components (the source toner), the cost and the availability the mixing components and the stability of the mixed components be considered producible mixed toner can be. The process is subsequently completed in step S62.

It can options for one reasonable preselection of for the mixture used colorants are provided. For example can the next the target color adjacent two or three output colorants (output toner with Output colors, compared to the output colors of another Output toners have a small color difference to the target color), to Generate the target color to be preset. Output colorants with a small color difference to the target color and a minimum number increase the starting colorant the stability the colorant mixture.

By additional bases also in only a part of the source space is the accuracy of the mapping function over the increased overall picture area.

Also in border areas of the color spaces, in which no test points are present, can be determined by the Mapping function is a color mapping of target and source colors easy to do with high accuracy.

Changes of basic parameters in the image formation, such as a change of the carrier material, the layer thickness of the generated color layers on the carrier material and / or output parameters of the output device as well as the measurement conditions for determining the color values can be taken into account in determining or determining a suitable mapping function. In particular, in addition to the proportions of the toners 1 to n and the color values, these parameters can be used as input variables and / or output variables in the artificial neural network 2 be used. By the described procedure, the actual process behavior of an output device, in particular a printer and the output colors that can be generated with the aid of the output device can be taken into account, without having to resort to idealized assumptions which would lead to errors. A knowledge of fundamental physical properties of these starting colorants essential for the color reproduction and the color behavior of the starting colorants in a colorant mixture is not absolutely necessary in the invention in contrast to the prior art.

The invention is particularly suitable for a color assignment between any color spaces. The color spaces are linked by a conversion of the color data with the help of the mapping function. The mapping function can take into account a raster process, a subtractive, additive and / or autotypical color mixing of a color conversion between two different output devices and / or further features of the source color space and the destination color space in the conversion process. The following table gives examples of conversion processes using a global mapping function of source colors of a source color space in target colors of a target color space by way of example: Source Space process Destination Space CMY Screening / overprinting CIELAB / CIEXYZ CMYK Screening / overprinting CIELAB / CIEXYZ CMYK + special color Screening / overprinting CIELAB / CIEXYZ CMYKRGB Screening / overprinting CIELAB / CIEXYZ R, G, B, C, M, Y, K subtractive color mixing / additive color mixing CIELAB / CIEXYZ CMYK Conversion printer 1 to printer 2 CMYK RGB additive color mixing CIELAB / CIEXYZ

at a formulation of target colors and while generating desired Colors from the basic colors cyan, magenta, yellow, black, are available a variety of possible Combinations of these primary colors to produce the same color impression. To one of these possible Select combinations, can Other properties of the starting colorants, such as the price, the Paint application, availability, the color fastness and miscibility become.

The Mapping regulation can be done in particular by a feed-forward backpropagation Neuronal Network. The number of free parameters is determined by the number of neurons in the hidden layer. As favorable has six different color image maps Output colors on a color value with three color coordinates one Number of six neurons in the hidden layer proved.

The free parameter of the mapping rule used in the feed-forward backpropagation Neuronal Network which are the weights of the neurons are going through one so-called training of the artificial neural network with target and source data of the test points below Application of a suitable training algorithm determined.

to Avoiding an underestimation of the system can create error bounds in the Reproduction of the test points are defined and their compliance checked. For an underdetermination of the system must be the number of free parameters elevated become.

To avoid system overdetermination, additional test points should be checked which have not been used to determine the mapping regulation, as related to 4 has been explained. For these additional test points, a source data pair and a target data pair are determined in the same way as for the other test points. The network is not overdetermined, although these other test points can be reproduced correctly using the mapping rule. However, if these test points deviate from the values determined using the mapping rule, the number of parameters must be reduced.

The target colors for producing suitable mixed toners can also be specified with reference to color sample collections, such as Pantone ^™ and as colors of a color table, such as the HKS color table, alternatively or in addition to the Lab color space.

Although in the drawings and in the foregoing description preferred embodiments have been shown and described in detail, this should be as purely exemplary and not restrictive to the invention become. It should be noted that only the preferred embodiments shown and described and all changes and modifications, currently and in the future are within the scope of the invention, to be protected.

10 12, 14

graphs

16 18

color values

toner 1

chromaticity first toner

toner 2

chromaticity second toner

toner 3

chromaticity third toner

S10 to S58

steps

Claims (26)

Method for determining a color assignment of Source colors and target colors, in which several different from each other Source colors of a source color space are selected, at least an output image is output with a representation of the selected source colors becomes, the color value of the output representation of each source color is determined as the target color in a target color space, and at with the help of the selected Source colors and the target color determined for each source color global mapping function is detected being with help This mapping function of each source color of the source color space one Target color of the target color space and / or each target color of the target color space at least one source color of the source color space can be assigned. Method according to claim 1, characterized in that that an output device Output data are output for outputting the determined source color, so the output device the desired generated target color generated. Method according to one of the preceding claims, characterized characterized in that by means of the mapping function, a color management carried out where the source color assigned to a target color to be output is is determined. Method according to one of the preceding claims, characterized characterized in that the target colors of the target color space using of the CIELAB color model and the source colors of the source color space Help of the CMYK color model to be discribed. Method according to one of the preceding claims, characterized characterized in that the mapping function is a mathematical function, preferably an n-th order polynomial and / or a neural network, includes. Method according to one of the preceding claims, characterized characterized in that the target color space by the for outputting Representations of target colors of available source colors limited and that the source color space is to provide a color management system limited to the target color space and / or adapted to the target color space. Method according to one of the preceding claims, characterized in that at least three different source colors, preferably 10 to 50 source colors, are selected which are used as vertices for determining the global mapping function. Method according to one of the preceding claims, characterized characterized in that the output image by means of a printer or Copier, preferably by means of an electrographic printer or copier, outputting the mapping function for the printer or copier is determined and preferably for providing a profile of the printer or copier for color management. Method according to claim 8, characterized in that that in each case a mapping function, preferably a profile of Printer or copier, for different output parameters, preferably for different ones support materials and / or different layer thicknesses is determined, wherein a global mapping function is determined, which is the selection of a Taken into account output parameters from at least two possible output parameters. Method according to claim 9, characterized in that that first source colors and a first output parameter, and at least second source colors and at least one second output parameter are selected, wherein the determined global mapping function dependency the target colors are taken into account by the respective output parameter. Method according to claim 9 or 10, characterized that the number of selected first source colors larger than the number of selected second source colors is, being a part of the first and a part preferably match the second source colors. Method according to one of claims 9 to 11, characterized that the output parameter comprises a fixed carrier material, wherein as a carrier material different types of paper, preferably coated and uncoated Papers, to be used. Method according to one of the preceding claims, characterized in that subsequently at least one further source color selected becomes, that an output image with the representation of the selected others Source color is output, that the color value of the output Display of the further source color determined as the target color in a target color space will, and that with the help of all selected source colors and the too each source color determined target color a new global mapping function is determined. Apparatus for determining a color assignment of Source colors and target colors, with an image output unit, the Output images with representations of selected different source colors outputs, with first means for determining a color value the output representation of each source color as the destination color value, and with second means for determining a global mapping function with the help of the selected Source colors and the destination color determined for each source color, where with the help of this mapping function of each source color of the source color space a target color of the target color space and / or any desired one output target color of the target color space at least one source color the source color space can be assigned. Method for determining an association of the mixed color a colorant mixture and the proportion of at least two starting colorants on the colorant mixture, with a first starting colorant a first starting color and at least a second starting colorant a second source color, wherein by different proportions the respective starting colorant on the colorant mixture from each other different colorant mixtures, each with a mixed color producible are, several different colorant mixtures be generated, one test print each with each colorant mixture is produced, the mixed color of each colorant mixture Determining the color values of the test prints is determined and with the aid of the portions of the starting colorant in the one another different colorant mixtures and to each colorant mixture determined mixed color determines a global mapping function is, with the help of this mapping function each proportion of the at least two starting colorants on the colorant mixture a Mixed color and / or a predetermined mixed color at least one proportion of the at least two starting colorants can be assigned to the colorant mixture are. Method according to claim 15, characterized in that that with the help of the determined mapping function the required Shares of the first output colorant and at least the second Starting colorant on a colorant mixture to produce a desired predetermined mixed color is determined. Method according to one of claims 15 or 16, characterized that at least three starting colorants with three different Output colors are used, with a mapping function for with Help of the at least three source colors displayable color space is determined, where for every possible one Combining the starting colorant a suitable colorant mixture with proportions of the starting colorants contained in the combination is determined, the actual Mixed color of the desired specified target color is close or matches with this. Method according to claim 17, characterized in that that a first combination of the first source colorant and the second source colorant, a second combination the second colorant source and the third source colorant, a third combination colorant first Starting colorant and the third starting colorant and a fourth combination the first starting colorant, the second starting colorant and the third starting colorant, wherein for each of these combinations a colorant mixture with proportions of the respective combination covered starting colorant is determined by means of the imaging function certain mixed color of the given target color comes closest. Method according to claim 18, characterized that a legal one Color difference between the one determined by means of the mapping function Mixed color and the desired Target color is set, that with the help of the mapping function selected mixed colors whose color distance to the desired target color is less than the permissible Color separation is, and that selection parameters are preset, with the help of which one of the selected mixed colors assigned Combination for producing the colorant mixture is determined. Method according to claim 19, characterized that the selection parameters a necessary layer density of the colorant mixture, a maximum layer thickness of the colorant mixture, the number of starting colorants, the availability the starting colorant and / or the cost of the starting colorant. Method according to one of claims 15 to 20, characterized that the mapping function is a mathematical function, preferably an nth order polynomial and / or a neural network. Method according to one of claims 15 to 21, characterized that for producing mixed colors between two and twenty starting colorants, preferably between four and ten, especially four to eight, starting colorants be provided with different starting colors from which a suitable colorant mixture with a combination of proportions is generated from two to four starting colorants. Apparatus for determining an association of the mixed color a colorant mixture and the proportion of at least two starting colorants on this colorant mixture, with a first starting colorant a first starting color and at least a second starting colorant a second starting color, using the starting colorant by different proportions of the respective starting colorants on the colorant mixture mutually different colorant mixtures can be produced with one mixed color each, with first means for producing mutually different colorant mixtures, With an image generation unit for generating at least one test expression each with each of the colorant mixtures produced, with second means for determining the color value of the test prints through which the mixed color the respective ones used to generate the respective test expression Colorant mixture is determined and with third means to Determine a global mapping function using the proportions the starting colorant in the mutually different colorant mixtures and the mixed color determined for each colorant mixture, wherein with the help of this mapping function each share ratio of at least two starting colorants on the colorant mixture a Mixed color and / or a predetermined mixed color at least one share ratio the at least two starting colorant on the colorant mixture are assignable. Method for determining the proportions of a first starting colorant and at least one second Starting colorant for producing a colorant mixture in which the proportion of the first starting colorant agent and the proportion of the second starting colorant for producing a colorant mixture with a predetermined mixed color by means of a global mapping function is determined. Device for determining the proportions of a first Starting colorant and at least one second starting colorant for producing a colorant mixture, with funds that with Help a global mapping function the proportion of the first source colorant and the proportion of the second source colorant for producing a Colorant mixture of a desired Determine predetermined mixed color. Method according to one of claims 15 to 22 or 24 or Device according to one of claims 23 or 25, characterized in that the starting colorants each Starting toner and the colorant mixture are mixed toner or that the starting colorants and the colorant mixture each liquid colorants, in particular printing inks or printing inks, are.