Patent Description:
<CIT> describes an on-page inkjet printhead spitting system that purges the printhead nozzles across the printed page, and occasionally in the conventional service station spittoon. In addition to the image-forming droplets, extra purging droplets are fired to maintain pen health. To determine when to purge each nozzle, the number of times each nozzle is fired to print the image is counted or estimated, or printhead characteristics are monitored. The purging dots may be located on the page, in the spittoon, or both.

Various features of the present disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate features of the present disclosure, and wherein:.

In the following description, for purposes of explanation, numerous specific details of certain examples are set forth. Reference in the specification to "an example" or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in at least that one example, but not necessarily in other examples.

Commercially available printers may include a printhead for ejecting printing liquid, such as an ink, through a nozzle, or a plurality of nozzles, during a printing image in order to form an image. In the case when solvent or water-based printing liquid is used, a reduction in print quality may arise due to evaporation from the nozzles between printing liquid ejection, or firing, of the nozzles, which may reduce print quality as printing liquid dries out and partially or fully clogs the nozzle. This may obstruct the passage of printing fluid as it is ejected through the nozzle. To mitigate this, nozzles may be "capped" between use to prevent evaporation through the nozzles. For example, a nozzle cap may be attached to the nozzle to cover the opening of the nozzle and form a seal to prevent exposure to external environments. As used herein, "decap" refers to a situation when a nozzle is not capped, and thus a situation where evaporation may negatively affect printing quality and nozzle health. The printing liquid drying out on the nozzle may affect printing quality as when the nozzle is desired to be used for printing an image, passage of the printing liquid through the nozzle may be obstructed by ink residue, and consequently the printing liquid may not be deposited at the correct location on the printing medium. The size of the drop of printing liquid may also be different to the desired drop size due to the level of clogging of the nozzle.

As used herein, "decap time" of a nozzle is the shorter time of i) the amount of time since a nozzle was most recently decapped or serviced; and ii) the amount of time since a nozzle most recently ejected printing liquid. It is to be understood that in some examples, servicing of the nozzle may include ejecting printing liquid through the nozzle.

A printhead may include a plurality of nozzles which may be fired independently from one another. Therefore, each nozzle may have a different decap time. For example, a nozzle corresponding to a colour or print location that is infrequently used may spend more time in a state where the nozzle is neither capped nor fired as the printhead traverses across the printing medium, which may lead to a greater impact on nozzle health and printing quality for that particular nozzle.

The effects of decap on nozzle health and print quality may be mitigated by servicing the nozzle in a servicing area or ejecting printing liquid through the nozzle. When printing liquid is ejected through the nozzle, the passage of the ejected printing liquid may remove printing liquid residue from the nozzle. The process of ejecting printing liquid through a nozzle for the purpose of cleaning the nozzle (as opposed to a desired printing operation) may be known as "spitting".

Nozzle maintenance may be performed by spitting directly onto the printing medium. For example, as the printhead traverses a printing medium, in what is known as a swath, the printhead nozzles may fire at times and locations other than those designated for forming the printed image and eject printing liquid onto the printing medium in order to clean the printhead nozzles. This technique may be known as "spit on page". Performing spit on page may mitigate rapid deterioration of nozzle health and printing quality associated with decap. For example, in the case where a nozzle is not used frequently for printing the image, spitting on the page with said nozzle may refresh the nozzle, which may increase print quality.

However, in some circumstances the dots formed on the print medium through the use of spit on page may be visible in the final printed output, depending on the texture and colour of the spat dots. In particular, certain printing technologies may be particularly susceptible to visible dots associated with spit on page. For example, in dye sublimation printing, due to the dot gain after sublimation, spat dots may be more visible than with other printing techniques.

Certain examples described herein provide methods and systems for generating printed images while reducing artefacts in the desired print output caused by spit on page operation. For example, methods may be provided to limit the spitting of spit on page dots to designated "non-printing areas" such as in space between images being printed on a print medium.

<FIG> shows a printing system <NUM> according to an example of the disclosure. The printing system <NUM> may include a memory <NUM>, reservoir <NUM>, processor <NUM>, print job processing engine <NUM>, printhead <NUM> and a network module <NUM>. The skilled person will appreciate that a printing system <NUM> may comprise a number of other known components of which a description here is omitted, and that some components of the printing system <NUM> shown in <FIG> may be optional for the purposes of this disclosure.

The memory <NUM> may be configured to store instructions for the operation of the printing system. For example, the memory <NUM> may store instructions useable by the processor <NUM> to control the printing system <NUM> to print an image onto a printing medium.

Printhead <NUM> may include at least one nozzle for ejecting a printing liquid, such as an ink, an overcoat, a colour enhancer or the like, onto a printing medium to form an image. The printhead <NUM> may perform a spit on page operation to clean the at least one nozzle of the printhead <NUM>.

The printing system may operate on a printing medium. The printing medium may be a substrate onto which the printing system <NUM> prints an image using the printhead <NUM>. For example, the printing medium may be printing paper, cardboard, textiles, etc. The printing medium may be physically moved by the printing system <NUM>. For example, the printing medium may be a plurality of pages of printing paper which are kept in a storage part of the printing system <NUM> and passed one at a time through a space under the printhead <NUM> during printing. For example, the printing medium may be moved in a direction perpendicular to the direction of movement of the printhead <NUM> during printing. Alternatively, the printing medium may be static during printing, and the printhead <NUM> may perform all desired movement to print an image.

The printhead <NUM> may print an image onto the printing medium according to instructions received from the processor <NUM>. That is, the printhead <NUM> may operate under the control of the processor <NUM>. The printhead <NUM> may be connected to reservoirs <NUM> or cartridges for storing printing liquid until use of the printing liquid is desired. The printhead <NUM> may eject a plurality of printing liquids of different colours and may include different nozzles for ejecting different coloured printing liquids. The printhead <NUM> may also include different nozzles for ejecting printing liquid onto different areas of the printing medium. The printhead <NUM> may include means of capping the nozzles to prevent evaporation of the printing liquid, for example the printhead may include mechanical caps to cover an opening of a nozzle to prevent exposure to the external environment.

The printhead <NUM> may print onto the printing medium using printing liquid, which may be stored in a reservoir <NUM> until the printing liquid is to be used for printing of an image or for spitting. The reservoir <NUM> may contain a single printing liquid or several different printing liquids. The reservoir <NUM> may be sealed to protect the printing liquid from an external environment.

The printing system <NUM> may operate under the control of the processor <NUM>. The processor <NUM> may control the printhead <NUM> to print an image on the printing medium by ejecting printing liquid through the nozzles of the printhead <NUM> as the printhead traverses across the printing medium.

The processor <NUM> may include a print job processing engine <NUM>. The print job processing engine <NUM> may receive information relating to a print job from the network module <NUM>, including at least one image to be printed, and provide an output to the printhead <NUM> to cause the desired print job to be printed to a print medium. Furthermore, the print job processing engine <NUM> may analyse the received print information to determine where to spit dots of ink onto the print medium to provide spit on page operation and control the printhead <NUM> to spit printing liquid a the determine positions.

According to some examples, the print job processing engine <NUM> analyses the received print job information to determine regions in which images or text, i.e. a desired output, are to be printed to a print medium and designate these regions as printing areas. Remaining areas which are not associated with the desired printing output are then designated as non-printing areas. Generally, print jobs contain space between different images to facilitate finishing processes, etc, providing non-printing areas between the images.

The print job processing engine <NUM> is operable to create a spit on page dot pattern that is applied to the non-printing areas and not to the printing areas. This is achieved by performing an overlay merge of a layer containing the printing areas, including the received images or text, over a layer containing the spit on page dot pattern to cover the spit on page dot pattern in the printing areas. The print job processing engine <NUM> then generates a print output file comprising the at least one image and the spit on page dot pattern in the non-printing areas.

This results in spit on page dots being printed in the areas designated as non-printing areas as required to avoid a nozzle of the printhead <NUM> exceeding a certain decap time. However, no spit on page dots are printed in the areas designated as printing regions in which the at least one image is printed to the print medium. In this way, artefacts in the finished printed product may be reduced or avoided.

The printing system <NUM> of <FIG> may be, for example, an inkjet printing system, a dye sublimation printing system or a piezoelectric printing system. The skilled person would understand that the example printing system <NUM> and the following methods disclosed herein should not be limited to a particular type of printing system, but may be applied to any printing system which uses printing liquid susceptible to evaporation and nozzles which may be maintained by ejecting printing liquid.

<FIG> illustrates an example compositing processes for generating a print output file with spit on page dots limited to non-printing areas. Print job information <NUM> comprises a layout description <NUM> and one or more images <NUM>. Based on the layout information <NUM>, the print job processing engine <NUM> arranges the one or more images <NUM> in an image layer <NUM>. A spit on page background layer <NUM> is provided with a dot pattern for spit on page operation of the nozzles of the printhead <NUM>. The dot pattern may be generated based on the allowable decap times of individual nozzles in the printhead <NUM>, based on stored patterns, or any other method.

The print job processing engine <NUM> then rasterizes the two layers into a single output file <NUM> with the image layer <NUM> overlying the spit on page layer <NUM>. Thus, the spit on page dots of background layer <NUM> are only visible in non-printing areas of the rendered output <NUM> where no printed output is defined in the layout file <NUM>.

The skilled person will recognize that more than two layers may be used, for example, the layout <NUM> may define a plurality of layers each containing one or more images to be composited on top of a background spit on page layer <NUM> into the output file to result in a desired printed output with spit on page restricted to non-printed areas.

The compositing described above in conjunction with <FIG> may be performed in the print job engine <NUM> operating on a processor <NUM> of a printing system. According to some examples, the compositing may be performed on an external user station, providing the print job engine functionality, coupled to a printing system and the output file including spit on page dots transmitted to the printing system to be rendered to a print medium. In such arrangements, a driver software may be loaded on to the user system and may comprise information relating to decap times for one or more nozzles of the printhead <NUM>.

In some examples, a user system may transmit a print job to a print job engine located in a print server, which may be a cloud server. The print server may process the print job to generate a print output file in line with the compositing process of <FIG> and then forward the print output file including the spit on page dots to a printing system to be printed to a print medium.

<FIG> shows a method <NUM> according to an example of the disclosure. According to the method of <FIG>, print job information including at least one image is received <NUM>, for example via network module <NUM> by a print job engine processor <NUM>. The print job engine processor <NUM> determines a printing area corresponding to a region containing the at least one image to be printed and a non-printing area corresponding to a remaining region, based on the received print job information. For the area determined to be the non-printing area, a dot pattern to provide spit on page operation is provided <NUM> by the print job engine processor <NUM>. A print output file is then generated <NUM> comprising the spit on page dot pattern in the non-printed areas and the at least one image.

The print output file may then be transmitted to a printing apparatus to be printed to a print medium. In some examples, the print job engine may use the generated print output file to directly control a printhead and printing apparatus to print the at least one image to the print medium.

In some examples, the print job information may further include a layout description associated with the at least one image to define the layout of the printed areas of the print job.

<FIG> shows a further method <NUM> according to an example of the disclosure. According to the method <NUM> of <FIG>, print job information including a layout description and at least on image is received <NUM>, for example at print job engine <NUM>. A background layer <NUM> comprising a dot pattern for spit on page operation is provided <NUM>, and the at least one image and layout description are rendered <NUM> to an image layer <NUM>. The layers are composited <NUM> with the image layer <NUM> overlying the background layer <NUM> such that the dot pattern of the background layer <NUM> is covered by the at least one image of the image layer <NUM>, while the dot pattern remains visible in other areas not associated with the at least one image. The composited layers are then rasterized <NUM> to generate a print output file that can be used to control a printhead <NUM>, or transmitted to a print apparatus, to be printed to a print medium.

The skilled person would understand that the printhead or printhead nozzle "spitting" printing liquid could be referred to as the printhead or printhead nozzle "ejecting", "firing" or "depositing" printing liquid.

The skilled person would understand that while this disclosure has been described with reference to components of a typical 2D printing system, the disclosure could equally be applied to a 3D printing system or any other type of printing system provided implementing spit on page to avoid problems with decap of nozzles.

Certain methods and systems as described herein may be implemented by one or more processors that processes program code that is retrieved from a non-transitory storage medium. <FIG> shows an example <NUM> of a device comprising a computer-readable storage medium <NUM> coupled to at least one processor <NUM>. The computer-readable media <NUM> can be any media that can contain, store, or maintain programs and data for use by or in connection with an instruction execution system. Computer-readable media can comprise any one of many physical media such as, for example, electronic, magnetic, optical, electromagnetic, or semiconductor media. More specific examples of suitable machine-readable media include, but are not limited to, a hard drive, a random-access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory, or a portable disc.

Claim 1:
A computer-implemented method of generating a print output file comprising:
receiving at least one image to be printed;
determining a printing area corresponding to a region containing the at least one image to be printed and a non-printing area corresponding to a remaining region;
providing a first layer comprising a spit-on-page dot pattern for the non-printing area, the spit-on-page dot pattern being for a spit-on-page operation, wherein the spit-on-page dot pattern of the first layer covers an entire output region of the print output file;
providing a second layer comprising the at least one image for the printing area ; and
generating the print output file comprising the spit-on-page dot pattern and the at least one image, wherein generating the print output file comprises compositing the first and second layers wherein the second layer overlies the first layer such that the dot pattern of the first layer underlying the printing area of the second layer are not visible and wherein the spit-on-page operation based on the print output file limits a spitting of spit-on-page dots according to the spit-on-page dot pattern to the non-printing area.