Color conversion method and system

Abstract

The present invention relates to a method of preparing print ready data. The method is adapted for converting first device specific print data for printing a multicoloured print job calorimetrically adapted to a first printing device or set of colorants, e.g. inks or toners, to print data calorimetrically adapted for a second printing device or set of colorants. The method comprises processing the data equally fast or faster than the print speed. The latter may be performed during printing, such that no halts are needed in between print jobs and the printing speed is mainly determined by the speed of the printing engine. The invention also relates to a corresponding system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 indicates a possible configuration for a digital print set-up combining three presses and a centralized department for job preparation, as may be subject to methods and systems according to embodiments of the present invention.

FIG. 2 indicates a possible configuration for a digital print set-up combining four presses and a centralized department for job preparation, as may be subject to methods and systems according to embodiments of the present invention.

FIGS. 3 and 4 indicate possible colour differences in colour gamut between two devices of a digital print set-up, as may occur in systems subject to methods and systems according to embodiments of the present invention.

FIG. 5 shows separate color transformation for two different devices of a digital print set-up as provided for in RIP color conversion.

FIG. 6 shows a process flow for color conversion between two different devices in a method according to embodiments of the present invention.

FIG. 7 shows possible colour differences in colour gamut between a 4-color based device and a 5-color based device, as can be used in embodiments according to the present invention.

FIG. 8. shows the correlation between different colour gamuts for different devices, as can be used in embodiments according to the present invention.

FIG. 9 and FIG. 10 show processing of files generated for Device A, Device D, Device C as well as SWOP for the extra-quaternary Device D, illustrating features of methods according to embodiments of the present example.

FIG. 11 indicates a scheme for post-processing transformation for color conversion according to an embodiment of the present invention.

FIG. 12 shows an exemplary configuration of a processing system, as can be used for performing the methods according to embodiments of the present invention.

FIG. 13 illustrates an example accelerator for performing the color transformation according to embodiments of the present invention.

In the different figures, the same reference signs refer to the same or analogous elements.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

The invention will now be described by a detailed description of several embodiments of the invention. It is clear that other embodiments of the invention can be configured according to the knowledge of persons skilled in the art without departing from the true spirit or technical teaching of the invention, the invention being limited only by the terms of the appended claims.

Where in the present application reference is made to “stream” or “streaming”, there is meant a technique for transferring data in real time such that it can be processed as a steady and continuous stream. In other words, when reference is made to “streaming”, the print system is provided with real time data.

The output gamut of a printing system can be defined as solid in a color space, consisting of all those colors that are capable of being created using a particular output device and/or medium. It is mainly determined by the position in L*a*b* of the primary colorants and the properties of color mixing of the inks or toners. Table 1 shows the typical L*a*b* values for colorants used in example print systems that could be used with the present invention. For clarification the outer contour of a projection of the gamut along the L* axis into the a*b* plane is used for graphical clarification in FIG. 3 and FIG. 4. FIG. 3 and

FIG. 4 show possible comparisons of the devices A and C and A and D, respectively, for the example of a system as illustrated in FIG. 2.

As can be noticed from FIG. 3 and FIG. 4 and the table 1 below, the main difference between the gamuts of the devices is to be related to the position in L*a*b* of the Magenta colorant.

System D has the more violet magenta, System C has a more reddish Magenta, while System A is closest to the ISO 12647-2.

	TABLE 1
	D	L*	a*	b*
	C-dev A	1.4	54.6	−24.2	−50.9
	M-dev A	1.4	50.4	63.4	−6.99
	Y-dev A	1.4	88.3	−10.2	83.1
	K-dev A	1.8	25.6	−0.31	−1.98
	M-dev D	1.4	47.8	66.2	−16.2
	Red	1.6	53.6	66.3	38.4
	C-dev C	1.4	54.9	−27.6	−51.5
	M-dev C	1.4	49.6	68.8	3.98
	Y-dev C	1.4	89.2	−5.42	86.3
	K-dev C	1.8	23.47	0.42	0.02

FIG. 5 represents a known color transformation as provided for in RIP color conversion using the terminology of PostScript as can be found in the PostScript Level 2 reference manual (third edition, Addison Wesley, 1999). Input- and output- profiles 12 such as ICC profiles that comply with the specifications of the ICC are converted to Color Space Arrays (CSA) 14 for input profiles. The 3-component profile connection space (PCS) 16 derived from models of tri-chromatic color vision by humans can be CIE XYZ for example (or L*a*b* as the Profile Connection Space (PCS) in the ICC-profile based color management). The PCS is a device independent color space. Since the XYZ color space is based on the human perception of color, any two different colors, even though the spectrum of these two colors may be different, will be perceived as the same color by a human if the XYZ values are the same under given lighting conditions. To make the print data device specific, Color Rendering Dictionaries (CRD) 18 are used to adapt the print data for output profiles, i.e. to generate device specific print data 20. The device specific print data 20 can be in the form of a device specific contone that is then halftoned or screened to form a binary or multilevel screened image.

The most straightforward approach in color management would be to have separate RIP processes as illustrated in FIG. 5 for the devices A and C. For example, the two RIP's could be performed using the same input images to thereby generate ready to print files 20 adapted calorimetrically to the print devices A and C, respectively. This requires twice the RIP processing and the storing of two or more fully ripped print jobs in order to be certain that there is no delay in the print room if one device is off-line.

An embodiment of the present invention is shown schematically in FIG. 6. In this process flow the RIP processing is carried out for the intended printing device A to generate print data 20 calorimetrically adapted to device A (CMYK(dev A)) as has been described for FIG. 5. For example; pint data 20 is in the form of a device specific contone image. If this device is not available for printing at the allotted time, the print data CMYK(dev A) is post-processed (process step=“devicelink”) 22 to new print data 24 calorimetrically adapted to device C (C′M′Y′K′ (dev C)). Such post processing may be performed in a fast way, e.g. equally fast or faster than the printing speed of the device to be used. The latter may allow streaming of the processed print ready data to device C, such that the processing may be performed simultaneously with the print task. The processing thereby may make use of a stored colour conversion algorithm, e.g. a stored colour conversion table or function for switching from one colour to another. The latter may be advantageous as it may assist in fast processing and result in reducing or avoiding halting between subsequent jobs as the colour conversion can be done simultaneously. In this way, halting and/or restarting of the print engine may be avoided, which otherwise would cause loss of productivity or causes generation of excess pages and thus an additional cost and optionally interference in later finishing steps.

A scheme for the devicelink transformation 22 in accordance with an embodiment of the present invention which is calorimetrically better than the operation of one dimensional look up tables can be a modified version of the one proposed in the ICC Specification ICC.1:2004-10 (Profile version 4.2.0.0) as shown schematically in FIG. 11 for transformation between a first and second device (A,B). This process can include matrix operations using pixel data from more than one of the color separations, and/or use of multidimensional look up tables and/or use of an interpolator to interpolate between values. A variety of methods can be used to complete the transform. Advantagously, the transform algorithm or corresponding data for performing the transformation may be previously stored, such that no overhead is induced by generation of colour conversion tables or by loading input and output profiles for the different devices at job time. For example, the process can include a first adaptation using one dimensional look up tables (LUT) followed by a matrix operation applied to all the separations followed by a further adaptation using one dimensional look up tables. In the case of a 4C-4C transformation a one dimensional adaptation “reverses” the device specific values of CMYK to a modified set ′C,′M,′Y,′K:

• • [′C]=LUT_C→C′[C]
  • [′M]=LUT_M→M′[M]
  • [′Y]=LUT_Y→Y′[Y]
  • [′K]=LUT_K→K′[K]which provides the adaptation from the Curve A of FIG. 11 related to the first device A.

A matrix operation then generates new values C″M″Y″K″

$\left[\begin{array}{c}{C}^{″}\\ M^{″}\\ Y^{″}\\ K^{″}\end{array}\right]=\left[\begin{array}{cccc}{a}_{11}& a_{12}& a_{13}& a_{14}\\ a_{21}& a_{22}& a_{23}& a_{24}\\ a_{31}& a_{32}& a_{33}& a_{34}\\ a_{41}& a_{42}& a_{43}& a_{44}\end{array}\right]\left[\begin{array}{c}{\hspace{0.17em}}^{\prime }C\\ {\hspace{0.17em}}^{\prime }M\\ {\hspace{0.17em}}^{\prime }Y\\ {\hspace{0.17em}}^{\prime }K\end{array}\right]$

and provides the transform shown in FIG. 11 referred to there as a multidimensional look up table. One aspect of the matrix multiplications is to provide intermediate values between known values by interpolation. Hence interpolation may be applied at any stage of this procedure to increase the number of values or to provide an new intermediate value.An optional further operation of a one dimensional adaptation can be as:

• • [C′]=LUT_C→C′[C″]
  • [M′]=LUT_M→M′[M″]
  • [Y′]=LUT_Y→Y′[Y″]
  • [K′]=LUT_K→K′[K″]which provides the adaptation to the device specific Curve B of FIG. 11.

Note that in this transformation there is no intermediate step of expressing the color value for each pixel in a color space, especially a 3 component color space such as XYZ, L*, a*, b* etc. followed by a further step of transformation back into CMYK space. Hence this is a direct transformation from CMYK to C′M′Y′K′ via one or more steps.

Alternatively the transformation can be made in a single matrix operation:

$\left[\begin{array}{c}{C}^{\prime }\\ M^{\prime }\\ Y^{\prime }\\ K^{\prime }\end{array}\right]=\left[\begin{array}{cccc}{a}_{11}& a_{12}& a_{13}& a_{14}\\ a_{21}& a_{22}& a_{23}& a_{24}\\ a_{31}& a_{32}& a_{33}& a_{34}\\ a_{41}& a_{42}& a_{43}& a_{44}\end{array}\right]\left[\begin{array}{c}C\\ \hspace{0.17em}M\\ \hspace{0.17em}Y\\ \hspace{0.17em}K\end{array}\right]$

Note that in these transformations there is no intermediate step of expressing the color value for each pixel in a color space such as XYZ, L*, a*, b* etc. followed by a further transformation back into CMYK space. Hence this is a direct matrix transformation from CMYK to C′M′Y′K′.

Other methods may use multidimensional look up tables. An example can be:

A first one dimensional the transformation:

• • [′C]=LUT_C→C′[C]
  • [′M]=LUT_M→M′[M]
  • [′Y]=LUT_Y→Y′[Y]
  • [′K]=LUT_K→K′[K]which provides the adaptation from the Curve A of FIG. 11 related to the first device A.

Followed by:

$\left[\begin{array}{c}{C}^{″}\\ M^{″}\\ Y^{″}\\ K^{″}\\ X\end{array}\right]={\mathrm{LUT}}_{{\hspace{0.17em}}^{\prime }C{\hspace{0.17em}}^{\prime }M{\hspace{0.17em}}^{\prime }Y{\hspace{0.17em}}^{\prime }K->C^{″}M^{″}Y^{″}K^{″}X}\left[\begin{array}{c}{\hspace{0.17em}}^{\prime }C\\ {\hspace{0.17em}}^{\prime }M\\ {\hspace{0.17em}}^{\prime }Y\\ {\hspace{0.17em}}^{\prime }K\end{array}\right]$

using the mulitdimensional LUT_{C′M′Y′K′→C″M″Y″K″} (see FIG. 11) if the transformation is from the space CMYK to the space CMYKX where X is an extra-quaternary toner.

Optionally additional transformations may be applied, e.g.

• • [C′]=LUT_C→C′[C″]
  • [M′]=LUT_M→M′[M″]
  • [Y′]=LUT_Y→Y′[Y″]
  • [K′]=LUT_K→K′[K″]corresponding to the adaptation to the device specific B curves of FIG. 11.

Note that in these transformations there is no intermediate step of expressing the color value for each pixel in a color space such as XYZ, L*, a*, b* etc. followed by a further transformation to the new CMYKX space. Hence this is a direct matrix transformation from CMYK to C′M′Y′K′X′. For additional colors the principles described above are extended.

Alternatively the transformation can be made in a single multidimensional Look Up Table operation:

$\left[\begin{array}{c}{C}^{\prime }\\ M^{\prime }\\ Y^{\prime }\\ K^{\prime }\\ X\end{array}\right]={\mathrm{LUT}}_{\hspace{0.17em}C\hspace{0.17em}M\hspace{0.17em}Y\hspace{0.17em}K->C^{\prime }M^{\prime }Y^{\prime }K^{\prime }X}\left[\begin{array}{c}\hspace{0.17em}C\\ \hspace{0.17em}M\\ \hspace{0.17em}Y\\ K\end{array}\right]$

Note that in these transformations there is no intermediate step of expressing the color value for each pixel in a color space such as XYZ, L*, a*, b* etc. followed by a further transformation back into CMYK space. Hence this is a direct matrix transformation from CMYK to C′M′Y′KX.

The matrix coefficients or the values in the look up tables can be obtained by proof printing the two printers and constructing the relevant values by optometric measurements and/or human test persons being used to examine and compare the results of printing on the two devices.

Converting to less than 4 separations like Grayscale (only K) or 2 colors (K+1) highlight color at print time is a useful feature and is also included within the scope of the present invention.

In a further aspect, if the color gamuts of device A and device C do not differ much the CMYK to C′M′Y′K′ transformation can be optimized as a devicelink profile taking into account preferred black generation as intended by a designer that is familiar with how to work with device A. Using a relative calorimetric approach for the devicelink process 22 will allow the pressroom manager to match the results that customers expect from device A when using device C. To the extent that the gamuts differ as indicated above according to FIG. 3 and FIG. 4, some colors will have to be mapped into the gamut of device C, e.g. if C is slightly smaller in the blue tones, or some of the red capabilities of device C will not be used.

In a preferred embodiment of the present invention, the devicelink transformation 22 as shown schematically in FIG. 6 is implemented as a separate and independent RIP-less step (e.g. post-RIP step) after completion of the RIP process.

The term “RIP-less” refers to the fact that all vector-based graphics have already been rendered to a raster format to generate the first print data 20 that is adapted calorimetrically to device A. The operations allowed in the RIP-less step are those allowed on the print data, e.g. in a print-ready format, complemented by one or more specific devicelink transformations.

In an even more preferred embodiment the devicelink transformation 22 as in FIG. 6 is implemented as a separate step that acts on a printer ready format. The printer ready format can be already stored, e.g. in permanent storage, in a computer system that streams the real time print data to the print engine of print device C.

Preferably, the devicelink transformation 22 of FIG. 6 acts on print data, e.g. in a print-ready format, at the same speed or higher than the print speed of device C, i.e. in a real time streaming process that keeps up with the print speed of the print engine of print device C.

Returning to FIG. 2 and FIG. 6, the printing system can include a graphics processing department 8 and a pressroom with printing devices 3, 5, 7, 9 each having a control system 11, 13, 15, 17, respectively. The control system can be a programmable microprocessor system. An operator creates print ready print data in the graphics processing department. Any of the print data may be a set of print files including variable data sets as in EP 1,111,545 A1. This print ready data is then processed in the control system where color management to adjust the print job to a different print device is carried out, and then the relevant print device prints. By using variable data sets, the conversion can be performed on the variable sets only, by caching them and further processing them such that these can be converted on the fly as they are assembled or generated. The latter avoids that complete sets of finished pages need to be retargeted which would be inefficient, especially as initially pages are often generated at run time in very long automatic series. In other words, it may be avoided that full printready bitmap of all the pages of a variable data job of significant size need to be generated and then converted.

The print job can contain objects such as color images, graphics and/or text, e.g. from scanned images, computer programs, or other generation means to create a composite image. The resulting contone image or native file can be converted into a page description language (PDL), e.g. Postscript. The PDL file can include contone data (for images), text data, and graphic data. The image is then raster image processed and can be stored in memory, e.g. on a hard disk. RIP-ing can be done with a RIP processor which decomposes or RIPs the PDL file into a contone separations, i.e., a byte maps. The print job is then transferred to the print room and is input to a specific print device, e.g. via a Local Area Network. A press operator can use the control system of the print device, e.g. via menu options, to adjust the parameters of a print job. In particular, contone print data may be modified post-RIP so that it can be printed on another device or with another set of toners than was originally planned in a calorimetrically true manner. Conventional post-RIP processing can also be carried out which is to be appreciated by those skilled in the art. The print engine of the print device can include a half-toner or screen generator which decomposes the color managed post-RIP contone print data into screened images for printing. In binary screened images, each screened separation is a bit map image or series of on and off instructions to tell the printer where to place an ink or toner dot of a particular process color or spot color on a printing medium. The present invention also includes multilevel generalizations of bitmaps as explained in EP634862 or U.S. Pat. No. 5,654,808.

In one aspect of the present invention, the printing is extra-quaternary printing.

The term “extra-trinary printing” or “extra-quaternary printing” can be used to describe printing with more than 3 or 4 subtractive colorants (toner, inks), respectively. Extra-quaternary printing comprises printing methods that are referred to as hi-fi color printing. In most cases the additional colorants are chosen in an attempt to extent the achievable color gamut. The present invention in one aspect relates to printing with 5 or more toners or inks.

Whereas the degrees of freedom of adding black to CMY leads to the concept of black substitution and grey component replacement (GCR) or under color removal, the addition of one or more R, G, B-like toners or inks can be looked upon as additional (secondary) chromatic toners or inks adding additional degrees of freedom in color separation that allow replacement certain combinations of primary (C,M,Y) inks by ink combinations including the secondary colorants.

For example, the use of Orange and Green toners in addition to primaries similar to C, M and Y is the basis of commercially relevant systems like Hexachrome. There are a number of contributions on separation strategies for 6-color and 7-color hifi systems. For designers to take advantage of the extended gamut that is accessible by extra-quaternary printing systems, there is a need for standardization.

Recently a number of vendors of Toner based Digital Printing Systems have launched products or described configurations with 5 print stations, e.g. D. Tyagi, P Alexandrovitch, Y. Ng, R. Allen and D. Herrick, IS&T NIP20 proceedings p 135-p 138. 5 color systems typically add one color to a 4 color ink set that approaches the CMYK of ISO 12647 or SWOP. In this way, the additional colorant extents the color space in a single direction. Although commercial device profile creation vendors start to provide tools to generate ICC profiles between the PCS and DeviceN output device spaces the use of such profiles imposes severe limitations on allowable input formats and typically excludes CMYK as explained in D. Tyagi, P Alexandrovitch, Y. Ng, R. Allen and D. Herrick IS&T NIP20 proceedings p 135-p 138.

Manipulating CMYK images to generate additional image separations is discussed in U.S. Pat. No. 5,870,530 and the corresponding EP 833 500 B1. These documents discuss issues with a simple substitution scheme where intermediate colors are used to replace equal amounts of primary colors or equal amounts of a two primary color overlay and a primary color.

The approach presented has the benefit of being simple and fast from a computational point of view. The scheme is oversimplified however as it assumes the substituting color provides a complete calorimetric match with the overlay of identical amounts of the combination of two primary colors it is supposed to replace,

There are several difficulties with a simple substitution scheme as in U.S. Pat. No. 5,870,530 that need to be countered for the method to work in a real workflow context:

1) The model proposes the use of a secondary colorant which is to be chosen such that a full layer of the secondary colorant replaces an overlay of the full layers of two of the primary colorants (e.g. 100% Red replaces 100% Y+100% M)

2) the deviations of L*a*b* of patches before and after the substitution differ too much to use this type of DeviceN (C,M,Y,K,X) images in a graphical context where color predictability and color management is a necessity.

The present invention provides an improved method and system for solving problem 1) by generalizing the model in allowing that the secondary colorant is to be chosen such that a full layer of the secondary colorant replaces an overlay of the optionally partial layers of two of the primary colorants (e.g. 100% Red replaces 90% Y+80% M). This flexibility allows the substitution to be adapted to the actual toner formulation chosen for the fifth colorant.

Even in this improved method, the relative colorimetric accuracy between the original patches and the colors printed using the fifth colorant using the substitution scheme can require additional color management to adapt the source images for colorimetric consistency. This means that a printer that would present itself as a new CMYK printer and that would implement the substitution method behind the screens would still require its own color profiles. In an embodiment, the present invention provides a RIP solution that allows to create multi-separation profiles with N separations, e.g. four color profiles such as CMYK output profiles for a printing system that converts the multi-separation profiles to profiles N+1, e.g. CMYK to CMYKX. Conversion from N separations to N+2, N+3 is also possible.

A perceptual approach that maps source images starting from CMYK has received little or no attention as there is no straightforward way of using the additional gamut based in the direction of the added color based on source data that uses the CMYK of the first four colorants.

Based on experiments, it has been found the color shifts induced by the change to the new ink combinations need to be corrected by traditional color management. As this color management is to be taken into account by measuring the overall system output and creating output profile for the new system, the prepress has to take into account the color transformation. As such there is no independence for the press management.

Simple substitution schemes in an ink jet context for converting combinations of primary colorants by secondary colorants as in U.S. Pat. No. 5,960,161, leave the color adjustments to traditional color management, resulting in the need for prepress to take into account the device specific color transformation.

The present invention in one aspect exploits the power of an N to N+M colorants conversion, where M can be one or more, e.g. any of the conversions 4C-5C, 4C-6C, 4C-7C, 4C-8C as a tool to simulate different presses and or standards in a relative calorimetric manner.

In the discussion of table 1 and FIGS. 3 and 4, it was noted that the magenta colorant can differ between toner versions for a given machine as well as between digital presses from different vendors that can co-exist in a pressroom. Study of 5C (five color) printing using a fifth colorant such as red has shown that if the red of table 1 is combined with a special choice for a non-standard magenta that is shifted away towards the violet from the proposed standards such as ISO 12647 (M-D for device D in table 1), a color gamut is obtained that comes close to being capable of relative calorimetrically correct rendering of the device CMYK gamut of devices A, D, C as well as the relevant standards.

FIG. 7 shows how the gamut of Device A is comprised within the gamut of the New Device E that is based on 5 colorants. FIG. 8 shows the gamut of device E in comparison to the gamut achieved with device D which corresponds to Device E with the 5th print station disabled and utilizing the special Magenta.

FIG. 9 and FIG. 10 shows how the extra-quaternary Device E can process files generated for Device A, Device D, Device C as well as SWOP by a separate process based on a devicelink transformation from 4C to DeviceN.

The devicelink transformation can act, for example, on a 4 channel CMYK input and results in an N channel output where N is different from 4. The devicelink transformation can act on a 4 channel CMYK input and results in an N channel output where N is larger than 4, i.e. N>4.

Accordingly the present invention includes a printing method using a deviceN printing system that supports a print mode in which it accepts already ripped or partly ripped image data as provided in device-specific CMYK or a standard CMYK print data wherein the conversion of the print data into a deviceN image is according to one of a set of pre-loaded 4C-NC conversion algorithms and is implemented as a separate step in or after the raster process.

The conversion can be from four colorants to a larger number such as five (i.e. N=5 in NC) in which three of the colorants correspond to C, Y and K and the fourth and fifth colorant (or more colorants) have a* value >55 as this is found to work well in providing means for emulation of presses that each use single but different magenta colorant. Even more preferred is a conversion can be from four colorants to a larger number such as five (i.e. N=5 in NC) in which three of the colorants correspond to C, Y and K and the fourth and fifth colorant (or higher number of colorants) have a* value >60.

In an advantageous embodiment of the present invention, the devicelink transformation 22 as in FIG. 6, 9 or 10 is implemented as a separate step after completion of the RIP process.

In an even more advantageous embodiment the devicelink transformation 22 as in FIG. 6, 9 or 10 is implemented as a separate step that acts on a print-ready format.

In an even more advantageous embodiment the devicelink transformation 22 as in FIG. 6, 9 or 10 is implemented as a separate step that acts on a print-ready format that is pulled from permanent storage by a computer system that streams the real time print data to the print engine of a print device.

Such method embodiments as are described above may be implemented in a processing system 150 associated with a print device 3, 5, 7, 9 such as shown in schematically in FIG. 12. FIG. 12 shows one configuration of processing system 150 that includes at least one programmable processor 153 coupled to a memory subsystem 155 that includes at least one form of memory, e.g., RAM, ROM, and so forth. A storage subsystem 157 may be included that has at least one disk drive and/or CD-ROM drive and/or DVD drive. In some implementations, a display system, a keyboard, and a pointing device may be included as part of a user interface subsystem 159 to provide for a user to manually input information or control data for steering the adaption of the print data received by the processing system to the alternative print device or set of toners. Ports for inputting and outputting data also may be included. More elements such as network connections, interfaces to various devices especially print devices, and so forth, may be included, but are not illustrated in FIG. 12. The various elements of the processing system 150 may be coupled in various ways, including via a bus subsystem 163 shown in FIG. 12 for simplicity as a single bus, but will be understood to those in the art to include a system of at least one bus. The memory of the memory subsystem 155 may at some time hold part or all (in either case shown as 161) of a set of instructions that when executed on the processing system 150 implement the step(s) of any of the method embodiments described herein. Thus, while a processing system 150 such as shown in FIG. 12 is prior art, a system that includes the instructions to implement novel aspects of the present invention is not prior art, and therefore FIG. 12 is not labelled as prior art.

It is to be noted that the processor 153 or processors may be a general purpose, or a special purpose processor, and may be for inclusion in a device, e.g., a chip that has other components that perform other functions, for example it may be an embedded processor.

Also with developments such devices may be replaced by any other suitable processing engine, e.g. an FPGA. Thus, one or more aspects of the present invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Furthermore, aspects of the invention can be implemented in a computer program product tangibly embodied in a carrier medium carrying machine-readable code for execution by a programmable processor. Method steps of aspects of the invention may be performed by a programmable processor executing instructions to perform functions of those aspects of the invention, e.g., by operating on input data and generating output data.

Furthermore, aspects of the invention can be implemented in a computer program product tangibly embodied in a carrier medium carrying machine-readable code for execution by a programmable processor. The term “carrier medium” refers to any medium that participates in providing instructions to a processor for execution. Such a medium may take many forms, including but not limited to, non-volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as a storage device which is part of mass storage. Volatile media includes mass storage. Volatile media includes dynamic memory such as RAM. Common forms of computer readable media include, for example a floppy disk, a flexible disk, a hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tapes, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereafter, or any other medium from which a computer can read. Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution. For example, the instructions may initially be carried on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to the computer system can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to a bus can receive the data carried in the infrared signal and place the data on the bus. The bus carries data to main memory, from which a processor retrieves and executes the instructions. The instructions received by main memory may optionally be stored on a storage device either before or after execution by a processor. The instructions can also be transmitted via a carrier wave in a network, such as a LAN, a WAN or the Internet. Transmission media can take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications. Transmission media include coaxial cables, copper wire and fibre optics, including the wires that comprise a bus within a computer.

One way to meet the requirement that the color transformation from a known printer ready format such as a CMYK printer ready format to the specific device-dependant ink-values can be done at faster than print-speed, is to provide programmable hardware to implement the sequence of LUT and matrix interpolations using for example a combination of dedicated and multi-purpose hardware components, including Field Programmable Gate (FPGA) arrays. An example of such an accelerator 40 will be described with reference to FIG. 13.

The accelerator 40 may be constructed as a VLSI chip around an embedded microprocessor 30 such as an ARM7TDMI core designed by ARM Ltd., UK which may be synthesized onto a single chip with the other components shown. A zero wait state SRAM memory 22 may be provided on-chip as well as a cache memory 24. One or various I/O (input/output) interfaces 25, 26, 27 may be provided, e.g. UART, USB, I²C bus interface as well as an I/O selector 28. These interfaces can connect to the Local Area Network 10 and to the print device with which the accelerator works. FIFO buffers 32 may be used to decouple the processor 30 from data transfer through these interfaces, e.g. to and from the network linking the print devices and the interface to the print device that uses the accelerator. A counter/timer block 34 may be provided as well as an interrupt controller 36. The devicelink transformation 22 of FIG. 6, 9 or 10 is provided by block 42 which can handle the matrix manipulations of the data. Block 42 may be configured around an FPGA and cooperates with the processor 30 for processing the print data. Software programs may be stored in an internal ROM (read only memory) 46. Access to an external memory may be provided an external bus interface 38 with address, data and control busses. The various blocks of accelerator 40 are linked by suitable busses 31.

Control mechanisms of the present invention to control the printing of print data may be implemented as software to run on processor 30. The procedures described above may be written as computer programs in a suitable computer language such as C and then compiled for the specific processor in the embedded design. For example, for the embedded ARM core VLSI described above the software may be written in C and then compiled using the ARM C compiler and the ARM assembler.

It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

Claims

1. A method of preparing print ready data comprising, obtaining first device-specific print data for printing a multicolored print job comprising multiple image source elements, the first print data having being generated by or in a raster image process and being calorimetrically adapted to a first printing device, andprocessing the first print data to generate print ready data calorimetrically adapted to a second print device, wherein the processing is performed at a speed equal to or faster than a printing speed of the second printing device.

2. The method according to claim 1, the method further comprising streaming said print ready data for printing with the second set of colorants or for printing with said second print device.

3. The method according to claim 1, wherein said processing of the first print data to generate print ready data uses at least one previously stored colour conversion table.

4. The method according to claim 1, wherein said processing of the first print data to generate print ready data uses a color conversion algorithm whereby the conversion is performed without transformation to a device independent color space.

5. The method according to claim 4, wherein said color conversion algorithm comprises a direct color conversion from a color space for the first printing device or for the printing with a first set of colorants to a color space for the second printing device or for the printing with a second set of colorants.

6. The method according to claim 1, wherein the first print data is a set of print files including variable data sets.

7. The method according to claim 1 wherein the first print data is print ready data.

8. The method according to claim 1 wherein the first print data is a device specific contone image.

9. The method according to claim 1, wherein the first print data and/or the print ready data are multicolored multipage print data for printing a multicolored, multipage print job.

10. The method according to claim 1 wherein the first print data has a first number of color separations, the print ready data has a second number of color separations and the second number of color separations is larger than the first number of color separations.

11. The method according to claim 1 wherein processing the first print data to generate print ready data calorimetrically adapted to the second print device includes adjustment of colors by manipulating print data across two or more color separations.

12. A method of preparing print ready data comprising, obtaining first print data by or in a raster image process for printing a multicolored print job comprising multiple image source elements, the first print data being calorimetrically adapted for printing with a first set of colorants, andprocessing the first print data to generate print ready data calorimetrically adapted for printing with a second set of colorants, there being at least one different colorant in the second set compared to the first set, wherein the processing is performed at a speed equal to or faster than a printing speed of the printing with a second set of colorants.

13. A system of preparing print ready data, comprising means for obtaining first device-specific print data for printing a multicolored print job comprising multiple image source elements, the first print data having being generated by or in a raster image process and being calorimetrically adapted to a first printing device,means for processing the first print data to generate print ready data calorimetrically adapted to a second print device at a speed equal to or faster than a printing speed of the second print device.

14. The system according to claim 13, the system further comprising a means for streaming print ready data for printing with a second set of colorants or for printing with a second print device.

15. The system according to claim 13, wherein the system comprises a memory for storing a previously determined colour conversion table and wherein said processing means is adapted to use said previously determined colour conversion table.

16. The system according to claim 13, wherein said means for processing is adapted for using a color conversion algorithm whereby the conversion is performed without transformation to a device independent color space.

17. The system according to claim 13, wherein said means for processing is adapted for performing a direct color conversion from a color space for the first printing device or for the printing with a first set of colorants to a color space for the second printing device or for the printing with a second set of colorants.

18. The system according to claim 13, wherein the first print data is a set of print files including variable data sets.

19. The system according to claim 13 wherein the first print data is print ready data.

20. The system according to claim 13, wherein the first print data has a first number of color separations, the print ready data has a second number of color separations, and the processor is adapted for between these data.

21. The system according to claim 13 wherein the means for processing the first print data to generate print ready data calorimetrically adapted to the second print device includes means for adjustment of colors by manipulating print data across two or more color separations.

22. The system according to claim 13, wherein the system is a control system associated with a print device.

23. A system of preparing print ready data comprising, means for obtaining first print data by or in a raster image process for printing a multicolored print job comprising multiple image source elements, the first print data being calorimetrically adapted for printing with a first set of colorants,means for processing the first print data to generate print ready data calorimetrically adapted for printing with a second set of colorants, there being at least one different colorant in the second set compared to the first set at a speed equal to or faster than a printing speed of the printing with the second set of colorants.

24. A method of preparing print ready data comprising, obtaining first device-specific print data for printing a multicolored print job comprising multiple image source elements, the first print data being generated using a raster image process and being calorimetrically adapted to a first printing device, andprocessing the first print data to generate print ready data colorimetrically adapted to a second print device, wherein the processing is a RIP-less process.

25. The method according to claim 24 wherein the processing comprises obtaining first print data during a RIP process.