System and method for preparing print data

Abstract

A system for preparing print data for one or more digital printing devices comprising: a first device configured to generate object data for one or more objects included in an image to be printed, and optionally layout data specifying how to generate a layout using said one or more objects; a second device comprising a processing unit configured to execute at least 200 threads in parallel and a memory, an interface between the first and the second device, wherein the second device is configured for receiving the object data, transforming said object data or a portion thereof, wherein optionally said transforming uses the layout data, wherein said transforming comprises at least a color transformation, screening said transformed object data or said portion thereof in order to obtain print data indicating for each pixel how the one or more digital printing devices need to be controlled.

Description

[0001] System and method for preparing print data

[0002] Field of Invention

[0003] The field of the invention relates to systems for preparing print data. Particular embodiments relate to systems and methods for preparing print data for one or more digital printing devices, such as one or more inkjet print heads or one or more imaging heads for transferring toner.

[0004] When printing in color with liquid ink or toner, it is known to perform object-oriented printing using multiple streamers connected to multiple distribution boards, for example for printing multiple lanes. Each distribution head is configured for powering one or more digital printing devices, for example multiple print heads for printing different colors. Such streamers are implemented in hardware, and the streamers may be interconnected through a high-speed backbone, such as a PCIe backbone. An object is sent to a first streamer, and if needed to a further streamer via the backbone. A controller in a computer is used to control the multiple streamers.

[0005] Such streamer is configured to perform first a color transformation, for example a color conversion from the color values of an image file (e.g., from a CIELab color space) to a color space for printing (e.g., a CMYK color space). More in particular, it is known to do color transformation on image files, e.g., using look-up tables. Such look-up tables may take into account the properties of the ink or toner, the substrate used, the type of digital printing device, etc. Next, the streamer screens the transformed object data which means that print levels are determined for each pixel. For example, for an inkjet print head, it may be possible to print with two different kind of ink droplets, so any of the following may be determined for each pixel: no printing, droplet type 1, droplet type 2. Similarly for dry toner, for each pixel a print level may be determined. To perform screening it is known to use threshold matrixes with threshold values which will determine which print level needs to be set for a pixel. In case of inkjet printing, after the screening, a nozzle mapping may be performed. Such nozzle mapping converts the screened data into the nozzle space. Examples of improved nozzle mapping methods are described in PCT specification WO 2019 / 180086 Al in the name of the applicant, which is included herein by reference.

[0006] In view of the above, existing streamers are complex hardware devices and the development of such devices takes a long time. Further, because such streamers are implemented in hardware they offer little flexibility in case of changes in the screening process. Summary

[0007] The object of embodiments of the invention is to provide an improved system for preparing print data which is more flexible and allows for a faster development of such systems.

[0008] According to a first aspect, there is provided a system for preparing print data for one or more digital printing devices. The system comprises a first device configured to generate object data for one or more objects included in an image to be printed, and optionally layout data specifying how to generate a layout using said one or more objects. The system further comprises a second device comprising a memory and a processing unit configured to execute at least two hundred threads in parallel. The system also comprises an interface between the first device and the second device. The second device is configured for receiving the object data and optionally the layout data through said interface, transforming said object data or a portion thereof, and screening the transformed object data or said portion thereof in order to obtain print data indicating for each pixel how the one or more digital printing devices need to be controlled. Optionally said transforming uses the layout data. The transforming comprises at least a color transformation.

[0009] By using a second device with a memory and a processing unit configured to execute at least two hundred threads in parallel, the color transformation and the screening can be performed in parallel for multiple scanlines, instead of scanline by scanline as in prior art solutions. Also, no complex hardware is needed and the steps of transforming and screening can be suitably programmed through software within a short time frame.

[0010] It is noted that the object data may be further transformed, and next screened, but it is also possible to perform the transforming and the screening in a combined manner. Also, only a portion of the object data may be transformed and screened, and then the next portion, etc.

[0011] Preferably, the interface has at least four lanes, more preferably at least eight lanes, even more preferably at least sixteen lanes. For example, the interface may comprise one or more Peripheral Component Interconnect Express, PCIe, interface devices. The speed of a lane of a PCIe device is very high compared to other interface devices. However, depending on the application, it may also be possible to use slower interface devices, such as an Ethernet or HDMI interface device.

[0012] Preferably, the memory of the second device is a memory of at least 4 GB, preferably at least 8 GB. This will allow to store for example more than 0.5m of scanlines (for example more than 20.000 scanlines). Preferably, the color transformation uses at least one look-up table, LUT, preferably one look-up table per color. Optionally, a multidimensional table may be used for all colors. For example, a (n x m)-color table may be used, with m the number of primary colors, and m = n, or m minimum 3 as in Lab. The transforming may comprise first merging the objects, then dividing the merged objects into blocks, and then transforming the blocks using a LUT. Alternatively, first the objects are transformed using a LUT, and next the objects are merged.

[0013] In an alternative embodiment functions and / or algorithms are used to perform the color transformation instead of LUTs.

[0014] Preferably, the processing unit is configured to perform single instruction multiple data, SIMD, processing. In an exemplary embodiment, the processing unit is a graphics processing unit. Such processing units are typically capable of performing many threads in parallel and thus well suited for embodiments of the invention.

[0015] Preferably, the processing unit is configured to execute at least 500 threads in parallel, more preferably at least 800 threads in parallel, even more preferably 1000 threads in parallel. This will allow to process for example more than 0.5m of scanlines in parallel, for example more than 20.000 scanlines.

[0016] Preferably, the second device is configured to execute at least 100 threads in parallel during the transforming and / or during the screening, preferably at least 200 threads in parallel.

[0017] Preferably, the first device is configured to compress the object data, wherein each object of said object data is compressed separately, so that the object data is compressed data, and wherein the second device is configured to decompress said object data prior to said transforming.

[0018] Preferably, the first device is configured to compress an object of the object data lossless or lossy depending on the type of object, and the second device is configured to decompress the object data accordingly. Lossless compression may use for example Run Length Encoding, RLE. Thus, different objects may be compressed in a different way. For example, line work may be coded lossless whilst other objects lay be compressed lossy.

[0019] In an exemplary embodiment, the first device comprises a central processing unit CPU and a memory, and the second device is configured to write directly into the memory of the first device through the interface without involvement of the CPU of the first device, and each digital printing device is connected through an interface having at least four lanes, preferably comprising one or more PCIe interface devices, to the first device. Although a PCIe interface is at present preferred, also other interfaces such as an Ethernet interface may be used instead.

[0020] In an alternative embodiment, the system further comprises said one or more digital printing devices, wherein each digital printing device is connected through an interface having at least four lanes, preferably comprising one or more PCIe interface devices, to the second device.

[0021] Preferably, the first device is configured to determine for said one or more digital printing devices at least one look-up table LUT, preferably based on digital printing device specific data and / or ink or toner specific data and / or substrate specific data, and to communicate said at least one look-up table to the second device, and wherein said second device is configured to perform said color transformation using said at least one look-up table for said one or more digital printing devices. In some embodiments the same LUT may be used for all printing devices, for example if the printing devices are identical, and the LUT may be only ink / toner dependent. Alternatively, the LUTs may be device-specific and optionally further dependent on the type of ink / toner and / or on the type of the substrate material on which the printing is being performed.

[0022] Preferably, the second device is configured to perform the screening by using at least one threshold matrix comprising threshold values for an area of pixels, wherein for each digital printing device a print level for each pixel is determined using said at least one threshold matrix. Lor inkjet, typically, one, two or three levels are being used. Lor dry toner more than three levels, for example nine levels, may be used.

[0023] It will be understood by the skilled person that a threshold matrix is a set of threshold values for different positions, and that this set does not be represented as a mathematical matrix. When two matrixes are being used this implies that there are two threshold values for a specific position. Thus, when the number of printing levels is two or more (0 or “no printing” not being counted as a level), preferably two or more threshold matrices are used. It is noted that instead of using multiple matrices which correspond with the different levels, also a multi-dimensional matrix with multiple values for each cell may be used.

[0024] Preferably, the one or more digital printing devices are one or more printheads, preferably one or more printheads for inkjet printing. Preferably, the one or more printheads are each configured to print at least two different types of ink droplet sizes and wherein the screening uses for each printhead at least two threshold matrices.

[0025] In embodiments with nozzle print heads, preferably the second device is configured to perform nozzle mapping on the print data so as to obtain nozzle data. More preferably, the second device is configured to perform said nozzle mapping by executing at least 100 threads in parallel, preferably at least 200 threads, for producing said nozzle data. The nozzle data may be nozzle data for nonoverlapping sets of nozzles. Optionally, also further nozzle data at a lower resolution may be prepared for the overlap regions in order to perform so-called stitching. This further nozzle mapping may be performed by executing for example at least 50 threads in parallel.

[0026] The nozzle mapping may be done in blocks, wherein typically all data for the nozzles that have to be fired simultaneously is prepared in one step. Examples of improved nozzle mapping methods are described in PCT specification WO 2019 / 180086 Al in the name of the applicant, which is included herein by reference.

[0027] Preferably, the second device is configured to perform nozzle compensation so as to obtain compensated object data which takes into account the operation of the nozzles.

[0028] In another exemplary embodiment, the one or more printing devices are one or more imaging heads configured to transfer toner.

[0029] In an exemplary embodiment the system further comprises a sensor such as a camera configured to sense data related to the operation of the one or more digital printing devices, and the second device is configured to take into account the sensed data or data based thereon. For example, the sensor may be configured to sense data allowing to derive if the printed color on a specific location in the printed image is correct, and wherein the second device may be configured to perform a correction for that specific location.

[0030] When the one or more digital printing devices are inkjet heads, preferably the second device is configured to perform the nozzle compensation based on the sensed data or the data based thereon, more preferably to perform a correction for the specific location. Inkjet printheads can have nozzles that are fully or partially blocked, resulting in not jetting, limited jetting, or jetting in a different direction than designed. Such jetting malfunctioning results in a color that is locally different because there is no ink where the defect nozzle should have printed. This type of defects can be very visible to the human eye. A common technique to compensate totally or partially for this type of defect is to use one or more neighboring nozzles to lay down more ink and thus make the local area where there is no ink smaller. This technique is called nozzle compensation. The one or more neighboring nozzles are often on the same printhead but can even be from a different printhead and even contain ink with a different color. For example, cyan ink may be compensated by black ink if the neighboring nozzles with cyan ink cannot compensate enough.

[0031] Thus, if a nozzle is not functioning properly, this may be compensated by suitable adapting the color mapping after the transforming and before the screening or by suitably adapting the printing level after the screening, such that one or more nozzles adjacent to the failing nozzle compensate for the failing nozzle. Although not preferred, it is also possible to do nozzle compensation after the layout and before the color transformation, or during the nozzle mapping. Preforming the nozzle compensation after the screening has the advantage that it is possible to compensate with neighbors in the line before and after the neighboring lines (so not direct neighbors of the failing nozzle).

[0032] When the one or more digital printing devices are imaging heads, also a correction may be performed based on sensed data. For example, dust that sticks to a high-voltage wire will result in a reduced electric field causing less toner to be transferred. This will result in lighter band at that location. This can be compensated by the second device by using a different color mapping which will result in different print levels. Indeed, a locally higher color mapping will result in a higher value going into the screener. A multi-level screener will then use more higher print levels.

[0033] Preferably, the second device is configured to transform the object data with an output of minimal 10 bits per pixel per color. For example, the input data may be represented by eight bits per pixel, and the eight bit per pixel input data may be transformed in ten bit per pixel output data. To that end, the color transformation may be done using one or more transformation tables, for example one table per color. Especially, when certain colors, such as certain types of orange, are being printed, 10 bits per pixel significantly increases the quality of the printed images.

[0034] Preferable, the second device is configured to perform said screening with an output of 1 , 2, 3 or 4 bits per pixel per color.

[0035] Optionally, the system further comprises a spectrophotometer configured to measure a color of a printed image and to communicate color data to the first or second device, and wherein the second device is configured to receive the color data or a modified look-up-table based on the color data and to take into account the color data or modified look-up-table to perform the transforming and / or the screening. Preferably, the first device is configured to generate layout data, and the transforming comprises performing laying out of said object data or a portion thereof based on said layout data to obtain laid out object data, and performing said at least a color transformation on said laid out object data. The layout data may comprise instructions on how to combine the one or more objects. For example, in case of one object, the layout data may indicate how many time the object needs to be repeated or in case of multiple objects, the instructions data may indicate the order and / or the position, etc.

[0036] Preferably, the second device is configured such that the number of threads executed by said processing unit in parallel is high enough to generate the print data to control the one or more digital printing devices at a speed which is not lower than 60% of a maximum printing speed of the one or more digital printing devices, more preferably not lower than 80% of the maximum printing speed, even more preferably 100% of the maximum printing speed. In that manner, the object data can be processed real-time by the second device, i.e. whilst printing with the one or more printing devices. Thus, preferably, the second device continuously processes consecutive object data and the one or more digital printing devices continuously print in accordance with said processed data.

[0037] According to a further aspect, the invention relates to the second device for use in any of the embodiments of the system described above.

[0038] According to a further aspect, the invention relates to the first device for use in any of the embodiments of the system described above.

[0039] Brief description of the figures

[0040] The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices of the present invention. The above and other advantages of the features and objects of the invention will become more apparent and the invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

[0041] FIGS. 1 and 2 illustrate schematically different exemplary embodiments of a system for preparing print data;

[0042] FIGS. 3 and 4 illustrate two possible implementations of the second device of a system according to the invention; and

[0043] FIG. 5 illustrates an exemplary embodiment of a system with a second device communicating with one or more sensors. FIG. 6 illustrates an exemplary embodiment of a system with a first device communicating with a spectrophotometer and a second device communicating with a camera. of embodiments

[0044] FIGS. 1 and 2 illustrate a first and second exemplary embodiment of a system for preparing print data for one or more digital printing devices 400. The system comprises a first device 100, a second device 200 and an interface 300 between the first device 100 and the second device 200. The one or more printing devices 400 may be one or more inkjet printheads comprising a plurality of inkjet nozzles, or one or more imaging heads configured to transfer toner.

[0045] The first device 100 is configured to generate object data for one or more objects included in an image to be printed, and layout data specifying how to generate a layout using said one or more objects based on the image. In some cases, for example when only a single object needs to be printed, no layout data will be generated. In other cases, the layout data may for example indicate how many times an object needs to be printed and / or data about where an object needs to be placed relative to another object, wherein optionally objects may overlap. Preferably, the first device 100 comprises a central processing unit CPU 110 and a memory 120.

[0046] The second device 200 comprises a memory 220 and a processing unit 210 configured to execute at least two hundred threads in parallel, preferably at least five hundred threads in parallel, more preferably at least eight hundred threads in parallel, even more preferably thousand threads in parallel. Preferably, the processing unit is configured to perform single instruction multiple data, SIMD, processing. The processing unit 210 is for example a graphics processing unit. Preferably, the memory 220 of the second device 200 is a memory of at least 4 GB, more preferably at least 8 GB.

[0047] The second device 200 is configured for receiving the object data and the layout data through interface 300, transforming said object data or a portion thereof. The transforming comprises performing laying out of said object data or a portion thereof based on said layout data to obtain laid out object data and performing at least a color transformation of said laid out object data. The second device is further configured for screening said transformed object data or said portion thereof in order to obtain print data indicating for each pixel how the one or more digital printing devices need to be controlled.

[0048] Preferably, the interface 300 has at least four lanes, preferably at least eight lanes, more preferably at least sixteen lanes. For example, the interface may comprise one or more Peripheral Component Interconnect Express, PCIe, interface devices. PCI Express is a switched architecture of up to 32 independent, serial lanes (xl-x32) that transfer in parallel. Each lane is full duplex.

[0049] Preferably, the color transformation uses at least one look-up table, LUT, preferably one look-up table per color. The first device 100 may be configured to determine for said one or more digital printing devices at least one look-up table LUT, preferably based on digital printing device specific data and / or ink or toner specific data and / or substrate specific data, and to communicate said at least one look-up table to the second device 200, and the second device 200 is configured to perform said color transformation using said at least one look-up table for said one or more digital printing devices 400. Preferably, the second device 200 is configured to transform the object data with an output of minimal 10 bits per pixel per color.

[0050] Preferably, the second device 200 is configured to perform the screening by using at least one threshold matrix comprising threshold values for an area of pixels, wherein for each digital printing device 400 a print level for each pixel is determined using said at least one threshold matrix. In an embodiment where the one or more digital printing devices 400 are one or more printheads configured to print at least two different types of ink droplet sizes and the screening may use for each printhead at least two threshold matrices. Preferably, the second device 200 is configured to perform said screening with an output of 1 , 2, 3 or 4 bits per pixel per color.

[0051] Preferably, the second device 200 is configured to execute at least hundred threads in parallel during the transforming and / or during the screening, preferably at least two hundred threads in parallel.

[0052] Preferably, the first device 100 is configured to compress the object data, wherein each object of said object data is compressed separately, so that the object data is compressed object data, and the second device 200 is configured to decompress 201 said object data prior to said transforming. More preferably, the first device 100 is configured to compress an object of the object data lossless or lossy depending on the type of object, and the second device 200 is configured to decompress the object data accordingly. Thus, different objects may be compressed in a different way. For example, line work may be coded lossless whilst other objects lay be compressed lossy. The combined compressed object data may thus comprise differently compressed objects.

[0053] In the embodiments of FIG. 1 the second device 200 may be configured to write directly into the memory 120 of the first device 100 through the interface 300 without involvement of the CPU 110. Each digital printing device 400 is connected through an interface 500 having at least four lanes, preferably comprising one or more PCIe interface devices, to the first device 100. In that manner data stored in the memory 120 of the first device 100 may be transferred in a fast manner to the one or more digital printing devices 400.

[0054] In the embodiment of FIG. 2 each digital printing device 400 is connected through an interface 600 having at least four lanes, preferably comprising one or more PCIe interface devices, to the second device 200. In that manner data stored in the memory 220 of the second device 200 may be transferred in a fast manner to the one or more digital printing devices 400.

[0055] In an embodiment where the one or more digital printing devices 400 are one or more printheads with nozzles, the second device 200 is configured to perform nozzle mapping on the print data so as to obtain nozzle data. The second device 200 may be configured to perform said nozzle mapping by executing at least 100 threads in parallel, preferably at least 200 threads, for producing said nozzle data. Also, the second device 200 may be configured to perform nozzle compensation so as to obtain compensated object data which takes into account the operation of the nozzles.

[0056] FIGS. 3 and 4 illustrate a possible implementation of the steps performed by the second device 200 for a system with one or more inkjet printheads 400 and for a system with one or more toner imaging heads, respectively.

[0057] Both in the embodiments of FIGS. 3 and 4, compressed object data is received and decompressed in a decompressor 201, whereupon the decompressed object data is being laid out based on received layout data in a merger (transformer) 202. Next the merger 202 performs a color transformation on the laid out object data, for example using one or more LUTs as explained above.

[0058] Then, the transformed object data is screened in a screener 203 to obtain a print level for each pixel to be printed. For inkjet, typically, one, two or three levels are being used. For dry toner more than three levels, for example nine levels, may be used. The screener 203 typically uses one or more threshold matrices. When the number of printing levels is two or more (0 or “no printing” not being counted as a level), preferably two or more threshold matrices are used. It is noted that instead of using multiple matrices which correspond with the different levels, also a multi-dimensional matrix with multiple values for each cell may be used.

[0059] In the embodiment of FIG. 3, optionally a nozzle compensation step (not shown) is included. If a nozzle is not functioning properly, this may be compensated by suitable adapting the color mapping after the color transformation and before the screening step or by suitably adapting the printing level after the screening step, such that one or more nozzles adjacent to a failing nozzle compensate for the failing nozzle

[0060] In the embodiment of FIG. 3, downstream of the screener 203, a nozzle mapper 204 is included. The nozzle mapper 204 converts the screened data into the nozzle space.

[0061] An example of a known inkjet head comprises a plurality of rows n, e.g. 16 rows, each having a plurality of nozzles m, e.g. between 100 and 200 nozzles, wherein the rows are oriented in a direction perpendicular to the printing direction, i.e. in the direction in which the substrate moves with respect to the inkjet head. Each row may have the same amount of nozzles or some rows may have a different amount of nozzles. Due to physical limitations, typically the rows are separated by more than one scanline, e.g. k scanlines where k may be e.g. between 10 and 30 scanlines. In typical known embodiments, the nozzles of the inkjet head may be fired substantially simultaneously. The firing frequency is such that each time the substrate has moved from one row to the next row a firing of all nozzles of the inkjet head is performed k times. The rows are shifted with respect to each other such that the combination of dots printed during subsequent steps of the printing process form a regular pattern. More in particular, when the inkjet head has fired all (n x m) nozzles k times while the substrate moves below the inkjet head, one line of the n lines extending perpendicular on the printing direction will be finished, and may comprise (n x m) dots. In other implementations, the nozzles of the inkjet head may be fired at different moments in time as disclosed in Dutch patent application No. 202008 lin the name of the applicant. Another example of a known inkjet head comprises an array of a plurality of rows (n) and columns (m), e.g. 32 rows (n = 32), each having a plurality of nozzles, e.g. 64 nozzles (m = 64), wherein the rows are oriented under a small angle with respect to a direction perpendicular to the printing direction, and the columns are oriented under a small angle with respect to the printing direction. Seen in a direction perpendicular to the printing direction, a plurality of such heads may be provided next to each other. During printing all (n x m) nozzles are fired substantially simultaneously with a firing frequency which is such that the nozzles fire at least every time the substrate has moved to the next row. Also using such an inkjet head, the distance between adjacent printed dots, seen in the printing direction, may be a factor smaller than the distance between adjacent nozzle rows.

[0062] The nozzle mapping step 204 maps the printing data to the nozzles and stores the nozzle data in the memory of the second device or directly in the memory of the first device using Direct Memory Access (DMA) controlling, from where it is transferred to the one or more printing devices. FIGS. 5 and 6 illustrate two further developed embodiments of the system. The system further comprises a sensor 700, such as a camera, configured to sense data related to the operation of the one or more printing devices 400, for example if the printed color on a specific location in the printed image is correct, and the second device 200 is configured to take into account the sensed data or data based thereon, for example to perform a correction for that specific location. In an embodiment where the one or more digital printing devices 400 are one or more printheads with nozzles, the second device 200 may be configured to perform the nozzle compensation based on the sensed data or the data based thereon, preferably to perform a correction for the specific location. Alternatively or in addition, the system may further comprise a spectrophotometer 700 configured to measure a color of a printed image and to communicate color data to the first device 100 (FIG. 6) or to the second device (FIG. 5), and the second device 200 is configured to receive the color data or a modified look-up-table based on the color data and to take into account the color data or modified look-up-table to perform the transforming and / or the screening.

[0063] Whilst the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.

Claims

Claims1. A system for preparing print data for one or more digital printing devices (400) comprising: a first device (100) configured to generate object data for one or more objects included in an image to be printed, and optionally layout data specifying how to generate a layout using said one or more objects; a second device (200) comprising a processing unit (210) configured to execute at least 200 threads in parallel and a memory (220), an interface (300) between the first device and the second device, wherein the second device (200) is configured for receiving the object data and optionally the layout data through said interface, transforming (202) said object data or a portion thereof, wherein optionally said transforming uses the layout data, wherein said transforming comprises at least a color transformation, screening (203) said transformed object data or said portion thereof in order to obtain print data indicating for each pixel how the one or more digital printing devices need to be controlled.

2. The system of claim 1, wherein said interface has at least four lanes, preferably at least eight lanes, more preferably at least sixteen lanes.

3. The system of claim 1 or 2, wherein the interface comprises one or more Peripheral Component Interconnect Express, PCIe, interface devices.

4. The system of any one of the previous claims, wherein said color transformation uses at least one look-up table, LUT, preferably one look-up table per color.

5. The system of any one of the previous claims, wherein said processing unit is configured to perform single instruction multiple data, SIMD, processing.

6. The system of any one of the previous claims, wherein said processing unit is a graphics processing unit.

7. The system of any one of the previous claims, wherein said processing unit is configured to execute at least 500 threads in parallel, more preferably at least 800 threads in parallel, even more preferably 1000 threads in parallel.

8. The system of any one of the previous claims, wherein the second device is configured to execute at least 100 threads in parallel during the transforming and / or during the screening, preferably at least 200 threads in parallel.

9. The system of any one of the previous claims, wherein the memory (220) of the second device is a memory of at least 4 GB, preferably at least 8 GB.

10. The system of any one of the previous claims, wherein the first device (100) is configured to compress the object data, wherein each object of said object data is compressed separately, so that the object data is compressed object data, and wherein the second device is configured to decompress (201) said object data prior to said transforming.

11. The system of the previous claim, wherein the first device (100) is configured to compress an object of the object data lossless or lossy depending on the type of object, and the second device is configured to decompress the object data accordingly.

12. The system of any one of the previous claims, wherein the first device (100) comprises a central processing unit CPU (110) and a memory (120), and wherein the second device is configured to write directly into the memory of the first device through the interface (300) without involvement of the CPU, and wherein each digital printing device is connected through an interface (500) having at least four lanes, preferably comprising one or more PCIe interface devices, to the first device.

13. The system of any one of the previous claims, further comprising said one or more digital printing devices, wherein each digital printing device (400) is connected through an interface (600) having at least four lanes, preferably comprising one or more PCIe interface devices, to the second device.

14. The system of any one of the previous claims, wherein the first device (100) is configured to determine for said one or more digital printing devices at least one look-up table LUT, preferably based on digital printing device specific data and / or ink or toner specific data and / or substrate specific data, and to communicate said at least one look-up table to the15 second device (200), and wherein said second device is configured to perform said color transformation using said at least one look-up table for said one or more digital printing devices.

15. The system of any one of the previous claims, wherein the second device is configured to perform the screening by using at least one threshold matrix comprising threshold values for an area of pixels, wherein for each digital printing device a print level for each pixel is determined using said at least one threshold matrix.

16. The system of any one of the previous claims, wherein the one or more digital printing devices are one or more printheads, preferably one or more printheads for inkjet printing.

17. The system of the previous claim, wherein the one or more printheads are each configured to print at least two different types of ink droplet sizes and wherein the screening uses for each printhead at least two threshold matrices.

18. The system of claim 16 or 17, wherein the second device is configured to perform nozzle mapping on the print data so as to obtain nozzle data.

19. The system of the previous claim, wherein the second device is configured to perform said nozzle mapping by executing at least 100 threads in parallel, preferably at least 200 threads, for producing said nozzle data.

20. The system of any one of the claims 16-19, wherein the second device is configured to perform nozzle compensation so as to obtain compensated object data which takes into account the operation of the nozzles.

21. The system of any one of the claims 1-15, wherein the one or more printing devices are one or more imaging heads configured to transfer toner.

22. The system of any one of the previous claims, further comprising a sensor (700) such as a camera configured to sense data related to the operation of the one or more printing devices, for example if the printed color on a specific location in the printed image is correct, and wherein the second device is configured to take into account the sensed data or data based thereon, for example to perform a correction for that specific location.1623. The system of claim 20 and 22, wherein the second device is configured to perform the nozzle compensation based on the sensed data or the data based thereon, preferably to perform a correction for the specific location.

24. The system of any one of the previous claims, wherein the second device is configured to transform the object data with an output of minimal 10 bits per pixel per color.

25. The system of any one of the previous claims, wherein the second device is configured to perform said screening with an output of 1 , 2, 3 or 4 bits per pixel per color.

26. The system of any one of the previous claims, further comprising a spectrophotometer (700) configured to measure a color of a printed image and to communicate color data to the first or second device, and wherein the second device is configured to receive the color data or a modified look-up-table based on the color data and to take into account the color data or modified look-up-table to perform the transforming and / or the screening.

27. The system of any one of the previous claims, wherein the first device is configured to generate layout data, and wherein said transforming (202) comprises:- performing laying out of said object data or a portion thereof based on said layout data to obtain laid out object data,- performing said at least a color transformation on said laid out object data.

28. The system of any one of the previous claims, wherein the second device is configured such that the number of threads executed by said processing unit in parallel is high enough to generate the print data to control the one or more digital printing devices at a speed which is not lower than 60% of a maximum printing speed of the one or more digital printing devices, preferably not lower than 80% of the maximum printing speed, more preferably 100% of the maximum printing speed.

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