Patent Application
20210039408
Images are processed for use with computing machines, such as a print apparatus. A print apparatus, for example, may use control data based on processed image data to reproduce a physical representation of an image by operating a print fluid ejection system according to the control data. Image processing may include color calibration. An image may be processed in a print apparatus pipeline or processed offline on separate compute device, such as a print server.
In the following description and figures, some example implementations of print apparatus, imaging systems, and/or methods of operating a carriage of a printer comprising are described. In examples described herein, a “print apparatus” may be a device to print content on a physical medium (e.g., paper, textiles, a layer of powder-based build material, etc.) with a print material (e.g., ink or toner). For example, the print apparatus may be a wide-format print apparatus that prints latex-based print fluid on a print medium, such as a print medium that is size A2 or larger. In some examples, the physical medium printed on may be a web roll or a pre-cut sheet. In the case of printing on a layer of powder-based build material, the print apparatus may utilize the deposition of print materials in a layer-wise additive manufacturing process. A print apparatus may utilize suitable print consumables, such as ink, toner, fluids or powders, or other raw materials for printing. In some examples, a print apparatus may be a three-dimensional (3D) print apparatus. An example of fluid print material is a water-based latex ink ejectable from a print head, such as a piezoelectric print head or a thermal inkjet print head. Other examples of print fluid may include dye-based color inks, pigment-based inks, solvents, gloss enhancers, fixer agents, and the like.
Certain examples described herein relate to color calibration of a print system. For example, color calibration may be used to adjust the color response of the print system to more accurately correspond to a desired color to be printed. Color calibration may be used to calibrate a color mapping process by which a first representation of a given color is mapped to a second representation of the same color. The concept of “color” can be represented in a large variety of ways, such as in relation to a power or intensity spectrum of electromagnetic radiation across a range of visible wavelengths or a color model is used to represent a color at a lower dimensionality. A “color” may be said to be a category that is used to denote similar visual perceptions where two colors are said to be similar if they produce a similar effect on a group of one or more people. These categories can then be modelled using a lower number of variables. In an example printing pipeline, individual inks may be calibrated separately so that printed colors are similar to or match desired colors.
A color model may define a color space, i.e., a multi-dimensional space with dimensions of the space representing variables within the color model and a point in the multi-dimensional space representing a color value. For example, in a red, green, blue (RGB) color space, an additive color model defines three variables representing different quantities of red, green and blue light. Another color space includes a cyan, magenta, yellow and black (CMYK) color space, in which four variables are used in a subtractive color model to represent different quantities of colorant or ink, e.g., for a print system and an image with a range of different colors can be printed by overprinting images for each of the colorants or inks. Yet other examples include: the International Commission on Illumination (CIE) 1931 XYZ color space, in which three variables (‘X’, ‘Y’ and ‘Z’ or tristimulus values) are used to model a color; the CIE 1978 (L*, a*, b*—CIELAB or ‘LAB’) color space, in which three variables represent lightness (‘t’) and opposing color dimensions (‘a’ and ‘b’); and the Yu′v′ color space, in which three variables represent the luminance (‘Y’) and two chrominance dimensions (u′ and v′). Other spaces include area coverage spaces, such as the Neugebauer Primary area coverage (NPac) space, where each NPac vector may define the probability distribution for one or more colorant or ink combinations for each pixel in a haftone (e.g., a likelihood that a particular colorant or ink combination is to be placed at each pixel location in the halftone).
In thermal inkjet printing, nozzles are fired using pulses of energy through resistors. Heat accumulated during the firing process may change the properties of the liquid inside the print head. During runs using media greater than a A2 length, for example, the print head surface temperature may change as much as ten degrees Celsius from swath to swath (i.e., each pass of the print head over the media) and may generally change over the time of the print job. Such print head temperature changes may affect drop characteristics, such as drop weight and drop velocity. Color variation may result due to different drop characteristics changes and may yield customer dissatisfaction, especially when working with tiles with a consistent desired color if the result is different color variations among tiles.
Various examples described below relate to color adjustment for printing based on area fill characteristics of a print job using variable carriage delay. For example, color variation may occur in long print jobs and, by analyzing the image data for area fills that may produce color variation, print operations may be adjusted to inhibit variation in output color, including operations such as carriage movement. An area fill, as used herein, is an area greater than a threshold number of pixels that contains the same coloring and/or pattern. For example, an area may be an area fill region of size M×N when the region is larger than a 2 pixel threshold in the x or y direction (e.g., media width and media advance directions) and the pixels of the region are all designated to be the same color combination. An area fill region may be any shape including rectangular, square, triangular, circular, etc., or any free from shape that achieves the size thresholds. The continuous pixels of the area may have an image quality effect with respect to the entirety of the area. The color adjustment of an area of an image may involve identifying whether an area fill region exists, whether the color of the area is sensitive to carriage delay, and a change in delay between passes of the print carriage (i.e. interswath delay) to compensate for a potential color variation. By implementing a variable interswath delay based on the delay-sensitivity of a color, an area fill of that color may be uniform over the entire area fill (e.g., without color variation due to lengthy print jobs of the same color).
The carriage 102 represents mechanical structure to move along a path. For example, a printer carriage may include a print head receiving station for retaining a print head for ejecting print fluid on a print medium, where the print carriage is supported by a carriage beam across the width of a printer that allows the carriage to move along a scan axis over the width of the print medium.
The color variation engine 104 represents any circuitry or combination of circuitry and executable instructions to identify a potential color variation condition corresponding to an area fill region of image data 108 of a print job. For example, the color variation engine 104 may be a combination of circuitry and executable instructions to determine an area fill region of a print job is greater than a threshold size and determine whether the region is to be filled with a delay-sensitive color combination. A potential color variation condition represents a plurality of printing parameters corresponding to the image data of a print job that may generate a variation in color across a region that is intended to be the same color. For example, a print job larger than the print medium may be printed on and cut into tiles and then attached together, where a color in a first tile may look different from the same color in the second tile due to some variation of firing characteristics.
The color variation engine 104 identifies the potential color variation for a region of the image data 108 based on the size of the area fill region and the color of the area fill region. A color as discussed further herein is referred to as a color combination of colorant print fluid, which may include a combination of colorants within a color space of a printer to produce a particular color as well as the use of a single colorant to produce the color (e.g., use of cyan color ink to produce a cyan colored area fill region). Various color combinations may have differing sensitivity and limitations of area sizes before a color variation may occur. For example, a dark purple may not be sensitive to color variation from longer runs, while a light turquoise may be sensitive to color variation of runs of similar length. For another example, a green region may start to vary in hue after 30 swaths of the length of the print medium while an orange region may have variation after 20 swaths of the length of the print medium. Some color variations may be compensated for by increasing the interswath delay while printing the area fill, which may, as an example, give the print fluid more consistent firing properties. The colors may correspond to use with a print head, for example, the variation threshold may be based on the number of consecutive nozzle firings for a particular type of print head. For example, if any of the print heads with cyan, magenta, or yellow surpasses more than a certain number of consecutive nozzle firings in a swath, a color shift may occur over time based on changes to the surface of the print head, such as changes in temperature or amounts of print fluid sticking to the print head. Colors may be correlated for the purposes of delay determination based on print head configuration. For example, if cyan and black are fired out of a first print head and magenta and yellow are fired out of a second print head, the thresholds may be correlated to a combination of the colors corresponding to each print head.
The color variation engine 104 may determine which swaths correspond to an area fill region of image data of a particular color combination and determine the area fill region is prone to color variation, such as by comparing a number of swaths of the print job for the region to a variation threshold corresponding to the color combination. The color variation engine 104 may perform a densitometer analysis to identify primary color values to be used to print a region, where the combination of primary color values represents a color combination of the region. An area fill region may be identified when the primary color values are consistent for a threshold amount of firings corresponding to the region. The variation threshold may be predetermined or may be calculated from predetermined values. For example, the color variation engine 104 may use a data resource, such as a lookup table, that associates a color combination with a number of swaths corresponding to the variation threshold (e.g., the maximum number of swaths before a color variation is likely with that color). The color variation engine 104 may retrieve a color variation prone threshold amount from a lookup table that includes an array of sensitive colors and interswath delays corresponding to each of the sensitive colors, where the interswath delay may be used by the delay engine 106 to apply a change to movement of the carriage of the printer.
The color variation engine 104 may track the output of the swaths printing a color combination for more than a threshold number of swaths. For example, the color variation engine 104 may include a combination of circuitry and executable instructions to perform a densitometer analysis to observe a number of swaths that are to print a particular color combination, which may occur before the print job begins or before a set of swaths is performed. For another example, the color variation engine 104 may include a combination of circuitry and executable instructions to monitor color variations during printing, such as using active color sensors near the print zone to identify a difference between output of a previous swath and output of a subsequent swath. The size of the area fill region may be identified by a width of the area fill region (with respect to, for example, the scan axis of the carriage holding a print head to print the area fill region) and the length of the area fill region (with respect to, for example, the media advance direction, such as a number of swaths along the media advance direction where a swath may be the length a trench of nozzles of the print head to be coupled to the carriage of the printer).
The delay engine 106 represents any circuitry or combination of circuitry and executable instructions to apply a carriage delay strategy according to a potential color variation condition (e.g., the potential color variation condition identified by the color variation engine 104) and the size of the area fill region. For example, the delay engine 106 may be a combination of circuitry and executable instructions to identify an amount of time to delay between swaths based on the color and size of the area fill region identified by the color variation engine 104 and instruct the print carriage to perform the printing operations with the amount of time delayed in between a first and second pass corresponding to the region. The delay engine 106 may use predetermined information and/or calculations to identify the delay to apply to movement of the carriage when printing an area fill region of a particular size and a particular color. For example, the delay engine 104 may calculate an interswath delay based on the number of swaths of the print job for the area fill region and the number of swaths exceeding a variation threshold corresponding to the color combination, where the variation threshold may be a predetermined number of swaths corresponding to the color combination.
The carriage delay strategy represents any timing adjustments applied to carriage movement, whether uniform or variable. For example, the carriage delay strategy may be an outline of swaths categorized to include particular amounts of interswath delays, which may be delays in addition to mechanical delays under average operation or may be total delays desired between swaths. The amount of time to delay as discussed herein may be a variable amount of time less than one second and greater than zero.
The delay engine 106 uses the color information and the size information of the area fill to identify the amount of time to delay the carriage between swaths. The delay engine 106 may use other characteristics of the print job or status of the printer. For example, the delay engine 106 may determine an interswath delay based on a size of a number of tiles of the print job and a job length of the print job and determine an adjustment of the interswath delay based on the location of the area fill region compared to the size of the number of tiles. In that example, the delay may not be used for area fills that are near the same side of the spittoon of the printer, for example. As another example, the location of the area fill on the media may be used to make further adjustments or remove delay of the carriage where the travel time to the area fill region may be counted as part of the delay, such as travel time to the center of the media for an area fill at the center of the media.
In some examples, functionalities described herein in relation to any of
For example, the processor resource 222 may carry out a set of instructions to determine a trigger value corresponding to conditions that identify image data includes an area fill region of a threshold width and a color for the area fill region is prone to show color variation beyond a threshold amount, track a parameter of the image data corresponding to the area fill region, compare the tracked parameter to the trigger value to determine if the area fill region is being printed after a threshold number of swaths, and apply a change to a variable interswath delay of movement of a printer carriage corresponding to a printing operation for printing the area fill region beyond the threshold number of swaths when the parameters achieve the trigger value (e.g., change a variable interswath delay of the carriage when the area fill is to be printed after a threshold number of swath corresponding to the sensitivity level of the delay-sensitive color combination). For another example, the processor resource 222 may carry out a set of instructions to identify a number of consecutive swaths of the region that use the same color across the scan axis, identify a threshold number of swaths to be printed maintained in same color proportions of the region based on color values of the color for the area fill region, determine a number of subsequent swaths beyond the threshold number of swaths, evaluate the image data of the number of subsequent swaths against a previous swath, and delay movement of the carriage in between swaths according to the evaluation of the number of subsequent swaths to the previous swath. For yet another example, the processor resource 222 may carry out a set of instructions to determine that the color of the area fill region is a color sensitive color combination via a densitometer analysis to identify and associate a delay with the sensitive color combination based on a composition of the color compared to predetermined colors with color variation sensitivity when the area fill is to be printed after a threshold number of swaths corresponding to a sensitivity level of the delay-sensitive combination. For yet another example, the processor resource 222 may carry out a set of instructions to retrieve and use a lookup table entry corresponding to the color to identify a color variation trigger value or dynamically compute the trigger value of the color based on a composition of the color compared to predetermined colors with color variation sensitivity and a predetermined delay corresponding to the color variation sensitivity of the colors of the composition. For yet another example, the processor resource 222 may carry out a set of instructions to determine a job width and a job length from image data, the image data being raster image processed data and apply the change of the variable interswath delay of movement of the carriage based on a location of the area fill region with respect to a scan axis of the printer direction and a direction of a swath to be printed.
Although these particular modules and various other modules are illustrated and discussed in relation to
A processor resource is any appropriate circuitry capable of processing (e.g., computing) instructions, such as one or multiple processing elements capable of retrieving instructions from a memory resource and executing those instructions. For example, the processor resource 222 may be a central processing unit (CPU) that enables interswath delay adjustments by fetching, decoding, and executing modules 204 and 206. Example processor resources include at least one CPU, a semiconductor-based microprocessor, a programmable logic device (PLD), and the like. Example PLDs include an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable array logic (PAL), a complex programmable logic device (CPLD), and an erasable programmable logic device (EPLD). A processor resource may include multiple processing elements that are integrated in a single device or distributed across devices. A processor resource may process the instructions serially, concurrently, or in partial concurrence.
A memory resource represents a medium to store data utilized and/or produced by the system 200. The medium is any non-transitory medium or combination of non-transitory media able to electronically store data, such as modules of the system 200 and/or data used by the system 200. For example, the medium may be a storage medium, which is distinct from a transitory transmission medium, such as a signal. The medium may be machine-readable, such as computer-readable. The medium may be an electronic, magnetic, optical, or other physical storage device that is capable of containing (i.e., storing) executable instructions. A memory resource may be said to store program instructions that when executed by a processor resource cause the processor resource to implement functionality of the system 200 of
In the discussion herein, the engines 104 and 106 of
In some examples, the system 200 may include the executable instructions may be part of an installation package that when installed may be executed by a processor resource to perform operations of the system 200, such as methods described with regards to
The print apparatus 390 of
The color variation engine 404 includes program instructions (such as a conditions module 440, a track module 442, an area fill module 444, and a color module 446) to assist identification of a delay-sensitive area fill region of a print job request 470. The modules 440, 442, 444, and 446 may use the image data 460, the size lookup table 462, and/or the color lookup table 464 in performing operations when executed by a processor resource.
The conditions module 440 represents program instruction that when executed cause a processor resource to determine parameters, including a job width and length from raster image processed data (e.g., the image data 460 of
The delay engine 406 includes program instructions (such as a sensitivity module 448, location module 450, and variable time module 452) to assist identification of a delay to apply to movement of a printer carriage. The modules 448, 450, and 452 may use the image data 460, the size lookup table 462, and/or the color lookup table 484 in performing operations when executed by a processor resource.
The sensitivity module 448 represents program instructions that when executed cause a processor resource to the sensitivity of the area fill region identified by executing the area fill module 444 based on the color combination to be printed in the region identified by executing the color module 446. If multiple sections of color are to be printed in the region, the sensitivity to inform the delay engine may be based on the combination of colors or a sub-region (such as the region of the most sensitive color combination of the color combinations to be printed). The location module 450 represents program instructions that when executed cause a processor resource to identify a location of the region with respect to the media size and/or the position of along the scan axis of the printer and determine if any adjustments are to be made, increased, or decreased based on the location. The variable time module 452 represents program instructions that when executed cause a processor resource to identify the delay, including travel time to the location, and identify an adjustment in variable interswath delay to achieve the delay with respect to the average interswath delay, where, in that example, the variable interswath delay is customizable and the average interswath delay is a standard delay during average operation. Execution of the variable time module 452 may utilize a timing projection 468 corresponding to the amount of time corresponding to travel of the carriage for a swath or a region of swaths, where the projected timings may be adjusted based on the determinations of the delay engine 406 and carriage movement instructions 472 generated accordingly.
The carriage engine 408 represents circuitry or a combination of circuitry and executable instructions to generate instructions to apply a delay to movement of a carriage (such as instructions to adjust an interswath delay of a printer carriage among a number of passes) as determined by the delay engine 406. The carriage instructions 472 generated by the carriage movement engine 408 are applied to the motors in charge of actuation of the movement of the carriage or otherwise sent to the controller or other mechanism for operating the carriage with the identified delay.
At block 502, a delay-sensitive color combination is determined to be part of an area fill region and the size of the area fill is determined to be greater than a threshold. The operations at block 502 may include determining a region is an area fill, determining the area fill region of a print job is to include a delay-sensitive color combination, and determining that the area fill region has a width along a scan axis of the carriage that is greater than a threshold width corresponding to a sensitivity level of the delay-sensitive color combination. The operations at block 502 may identify a threshold size to achieve a color variation of a color combination and/or may identify a color combination sensitive at the size of the area fill region using predetermined resources, such as a lookup table, or by dynamically computing the threshold size and sensitivity and comparing the computations to a region of image data.
At block 504, a correction to movement of the carriage of the printer is applied after a threshold number of swaths corresponding to the sensitivity level of the delay-sensitive color combination identified at block 502. The operations at block 504 may include applying a change to movement of a printer carriage during a printing operation for printing the area fill region that extends beyond the predetermined number of swaths when the parameters achieve the trigger value (e.g., when the primary color values corresponding to pixels of the region achieve or exceed a size threshold and the color combination threshold).
At block 602, printing parameters of a print job, including a job width and a job length, are determined from raster image processed data. At block 604, a region of image data is determined to be an area fill from an internal densitometer information analysis operation performed on image data of the print job and is beyond the media width and/or the job length is beyond the media length. This generally indicates a tiling job is to be printed and the printer may print in a tiling mode (e.g., print images to be printed separately and then aligned together to make a final output image). With tiling jobs, it is desirable that the colors of each tile match, in particular when the same color of each tile are aligned adjacent to each other. For example, if there is a color variation on a first tile compared to a second tile, the variation may be readily detectable at the seam where the tiles are applied together. The internal densitometer information analysis may use primary color values corresponding to identify when a region includes an area fill.
At block 606 printing parameters are monitored. The printing parameters monitor may include a number of nozzles to fire a color combination, such as the color combination of the area fill region. At block 608, the area fill width of the area fill region is identified. The area fill width is compared to a threshold size corresponding to the color sensitivity level of the color combination of the area fill region. The width of the area fill may indicate whether a threshold level of area fill corresponding to a sensitivity level may be achieved. With the width of the area fill identified, the length of the area fill is to be identified to determine the size of the area fill. At block 610, the length of the area fill may be identified based on the printing parameters monitored at block 606. For example, the nozzles of a print head to be fired for a previous swath are compared with the nozzles of the print head to be fired a subsequent swath. In this manner, the print parameters of the swaths are compared to a threshold size corresponding to the color sensitivity level of the color combination of the area fill region. The thresholds may vary based on the color combination of the area fill, such that, at block 612, it is determined whether a region includes a delay-sensitive color combination and is a size greater than the threshold corresponding to color variation potential of the delay-sensitive color combination. At block 614, a change to a variable interswath delay is applied when the area fill exceeds the threshold size and the threshold number of swaths corresponding to the delay-sensitive color combination. In this manner, the delay is applied when the area fill region is large enough in both length and width corresponding to an amount of ink that may produce a color variation over time of the print job.
Referring to
At block 704, a section of image data corresponding to a scan axis is ascertained to be printed with a color combination. For example, a pass of a carriage of a print head may correspond to a set of image data, where a consecutive number of firings corresponding to the scan axis are to be printed in the same color combination. The operations at block 704 may also include ascertaining whether the color combination is sensitive to carriage delay or not.
At block 706, a threshold number of swaths is identified corresponding the color combination that achieves a sensitivity level of the color combination. The thresholds may vary based on the color combination of the area fill and may vary based on the sensitivity level being analyzed. The operations of block 706 may use a lookup table entry corresponding to the color to identify a color variation threshold (e.g., trigger value) at block 708 and/or dynamically compute the color variation threshold at block 710. The operations at block 710 to dynamically compute the color variation threshold may be based on a composition of the color compared to predetermined colors with color variation sensitivity and a predetermined delay corresponding to the color variation sensitivity of the colors of the composition.
At block 712, a swath is determined to print the section of image data in the same color combination beyond the threshold number of swaths, thus indicating a color variation potential and a corrective interswath delay should be applied (e.g., see blocks 504 and 614 of methods 500 and 600 respectively). By actively tracking the potential for color variation of area fill regions, movement of the carriage may be corrected according to encourage consistent colors across the entire print job, in particular across multiple tiles of the same job.
Although the flow diagrams of
All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the elements of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or elements are mutually exclusive.
The terms “include,” have, and variations thereof, as used herein, mean the same as the term “comprise” or appropriate variation thereof. Furthermore, the term “based on,” as used herein, means “based at least in part on.” Thus, a feature that is described as based on some stimulus may be based only on the stimulus or a combination of stimuli including the stimulus. Furthermore, the use of the words “first,” “second,” or related terms in the claims are not used to limit the claim elements to an order or location, but are merely used to distinguish separate claim elements.
The present description has been shown and described with reference to the foregoing examples. It is understood, however, that other forms, details, and examples may be made without departing from the spirit and scope of the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2018/019675 | 2/26/2018 | WO | 00 |
