Printing device, printing method, and non-transitory computer-readable storage medium for displaying preview images corresponding to results of gamut mapping processes

A printing device includes a printing unit and a controller. The controller performs: acquiring image data; acquiring an image color gamut that is a specific area of a predetermined color space occupied by color values included in the image data; receiving information on a first color that is specified by a user and is present in the image color gamut; executing, on the basis of whether the first color is present in a printing color gamut that is a specific area of the predetermined color space occupied by color values of colors printable by the printing unit, different gamut mapping processes on the image data; displaying, prior to printing based on the image data, the first color and preview images corresponding to results of the gamut mapping processes; and printing, using the printing unit, an image corresponding to the preview image selected by the user among the displayed preview images.

REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No. 2022-087829 filed on May 30, 2022. The entire content of the priority application is incorporated herein by reference.

BACKGROUND ART

Conventional technologies known in the art perform a prescribed process on image data when determining that the image data contains colors outside the printing color gamut. In a conventional technology, for example, when the image data includes colors outside the printing color gamut, a process is performed to modify a reference color in a direction different from a predetermined color changing direction and to determine whether a prescribed number of colors that are selected in the color changing direction and that include the modified reference color contain any colors outside the printing color gamut. This process is repeated until all selected colors fall within the printing color gamut.

DESCRIPTION

However, user satisfaction with the printed images tends to decrease even when colors outside the printing color gamut are processed to fit within the printing color gamut and images are printed on print media based on the processed image data.

In view of the foregoing, it is an object of the present disclosure to provide a printing device, printing method, and non-transitory computer readable storage medium that can increase user satisfaction in printed images.

In order to attain the above and other object, according to one aspect, the present disclosure provides a printing device including a printing unit and a controller. The printing unit is configured to print on a printing medium using colorants in prescribed basic colors. The controller is configured to perform: (a) acquiring image data; (b) acquiring an image color gamut, the image color gamut being a specific area of a predetermined color space that is occupied by color values included in the image data acquired in (a); (c) receiving information on a first color specified by a user, the first color being present in the image color gamut acquired in (b); (d) executing, on the basis of whether the first color is present in a printing color gamut, two or more gamut mapping processes on the image data acquired in (a), the two or more gamut mapping processes being different from each other, the printing color gamut being a specific area of the predetermined color space that is occupied by color values of colors printable by the printing unit; (e) displaying, prior to printing based on the image data acquired in (a), the first color and preview images corresponding to results of the two or more gamut mapping processes; and (f) printing, using the printing unit, an image corresponding to the preview image selected by the user among the preview images displayed in (e).

According to another aspect, the present disclosure provides a printing method using a printing device including a printing unit. The printing method includes: (a) acquiring image data; (b) acquiring an image color gamut, the image color gamut being a specific area of a predetermined color space that is occupied by color values included in the image data acquired in (a); (c) receiving information on a first color specified by a user, the first color being present in the image color gamut acquired in (b); (d) executing, on the basis of whether the first color is present in a printing color gamut, two or more gamut mapping processes on the image data acquired in (a), the two or more gamut mapping processes being different from each other, the printing color gamut being a specific area of the predetermined color space that is occupied by color values of colors printable by the printing unit; (e) displaying, prior to printing based on the image data acquired in (a), the first color and preview images corresponding to results of the two or more gamut mapping processes; and (f) printing, using the printing unit, an image corresponding to the preview image selected by the user among the preview images displayed in (e).

According to still another aspect, the present disclosure provides a non-transitory computer-readable storage medium storing a set of instructions for a printing device. The printing device includes a printing unit and a controller. The printing unit is configured to print on a printing medium using colorants in prescribed basic colors. The set of instructions, when executed by the controller, causes the printing device to perform: (a) acquiring image data; (b) acquiring an image color gamut, the image color gamut being a specific area of a predetermined color space that is occupied by color values included in the image data acquired in (a); (c) receiving information on a first color specified by a user, the first color being present in the image color gamut acquired in (b); (d) executing, on the basis of whether the first color is present in a printing color gamut, two or more gamut mapping processes on the image data acquired in (a), the two or more gamut mapping processes being different from each other, the printing color gamut being a specific area of the predetermined color space that is occupied by color values of colors printable by the printing unit; (e) displaying, prior to printing based on the image data acquired in (a), the first color and preview images corresponding to results of the two or more gamut mapping processes; and (f) printing, using the printing unit, an image corresponding to the preview image selected by the user among the preview images displayed in (e).

Next, printing devices according to embodiments of the present disclosure will be described while referring to the accompanying drawings. The printing devices in the following description are each merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiments, and elements may be added, omitted, and modified without departing from the spirit of the disclosure.

FIG.1is a perspective view illustrating the appearance of a printing device1according to one embodiment of the present disclosure. InFIG.1, three directions orthogonal to one another will be defined as a first direction Ds, a second direction Df, and a third direction Dz. In this embodiment, the first direction Ds is the moving direction of a carriage41described later, the second direction Df is the conveying direction of a print medium W described later, and the third direction Dz is the up-down direction, for example. Thus, in the following description, Ds will be called the moving direction, Df will be called the conveying direction, and Dz will be called the up-down direction.

As illustrated inFIG.1, the printing device1is an inkjet printer configured to print images on print media W (seeFIG.2), such as a printing paper. The exterior of the printing device1has a parallelepiped shape. The printing device1includes a printing unit2, and a scanning unit3. However, the printing device1inFIG.1is merely an example and is not limited to this configuration. For example, the printing device1may include a printing unit (ejection head) configured to eject UV-curable ink droplets, and a light source configured to cure the ink droplets with ultraviolet light.

The scanning unit3is configured to generate image data by reading images using an image sensor. The printing unit2is configured to print this generated image data on a print medium W either accommodated in the printing device1or supplied into the printing device1from outside. The scanning unit3is arranged on top of the printing unit2and is coupled to the printing unit2by coupling parts2aprovided on the rear portion of the printing unit2. When the front portion of the scanning unit3is lifted, the scanning unit3pivots upward about the coupling parts2a, exposing the inside of the printing unit2.

The scanning unit3includes a document platen7, and a cover8. The cover8is arranged so as to cover the top of the document platen7. The scanning unit3is configured to scan images recorded on an original while the original is positioned between the document platen7and cover8.

The printing unit2is configured to print images on print media W with ink supplied from tanks12described later. The printing unit2includes a case4that forms part of the housing of the printing device1. The case4has an opening that communicates with the interior of the case4. A cover6is mounted on the case4and is configured to open and close the opening of the case4. A tray5for accommodating the print media W is disposed inside the case4. The tray5can be pulled out to the front of the case4for replenishing print media W.

The tanks12store ink. The tanks12are exposed outside when the cover6is open. The tanks12are connected to ejection heads20(seeFIG.2) via channels for supplying ink to the ejection heads20.

As illustrated inFIG.2, the printing device1employs a serial head system and includes the ejection heads20, a platen11, the tanks12, a conveying device30, and a scanning device40. However, the printing device1may employ a line head system. In this case, the scanning device40is omitted from the printing device1, and the ejection heads20are immobile and have a length in the moving direction Ds that is greater than the printing area on the print medium W.

The ejection heads20use ink in basic colors (described later) to print images on print media W based on image data. Here, ink is an example of the colorants and the ejection heads is an example of the printing unit. The ejection heads20include two first ejection heads21, and two second ejection heads22, for example. The platen11has a flat top surface and defines the distance between a print medium W placed on this top surface and the bottom surfaces of the ejection heads20disposed so as to face this top surface. The tanks12are containers for storing ink. The number of tanks12is equal to or greater than the number of ink types. For example, the tanks12include four first tanks12athat respectively store ink in one of the four basic colors, and one or more second tanks12bthat store ink in special colors.

Examples of basic color inks are cyan ink, yellow ink, magenta ink, and black ink. Special color inks have different colors from the basic colors. Examples of special color inks are red ink, green ink, and blue ink.

The first tanks12astore ink in the basic colors and communicate with the first ejection heads21through first channels13a. Ink in the basic colors is supplied from the first tanks12ato the first ejection heads21via the first channels13a. The second tanks12bcommunicate with the second ejection heads22via second channels13b. When the second tanks12bstore ink in special colors, the special color inks flow from the second tanks12binto the second channels13b, filling the second channels13b. From the second channels13b, the special color inks are supplied to the second ejection heads22. Before ink in special colors is stored in the second tanks12b, the second tanks12bare filled with a storage solution different from the ink in special colors. The first channels13aand second channels13bare rubber tubes or plastic tubes, for example, which are preferably resistant to kinking.

The conveying device30includes two pairs of conveying rollers31, and a conveying motor32(seeFIG.3), for example. The two pairs of conveying rollers31are arranged in the conveying direction Df (front-rear direction) with the platen11interposed therebetween in the conveying direction Df Each of the conveying rollers31has an axis extending in the moving direction Ds. The two conveying rollers31in each pair are arranged in the up-down direction Dz and are configured to nip a print medium W therebetween. One conveying roller31in each pair is connected to the conveying motor32. The conveying rollers31rotate about their axes when driven by the conveying motor32and convey a print medium W over the platen11in the conveying direction Df.

The scanning device40includes the carriage41, two guide rails42, a scanning motor43, and an endless belt44. The two guide rails42extend in the moving direction Ds above the platen11with the ejection heads20interposed therebetween in the conveying direction Df. The ejection heads20are mounted on the carriage41. The carriage41is supported on the two guide rails42so as to be movable in the moving direction Ds. The endless belt44extends in the moving direction Ds and is attached to the carriage41. The endless belt44is also connected to the scanning motor43via a pulley45. When the scanning motor43is driven, the endless belt44circulates to reciprocate the carriage41in the moving direction Ds along the guide rails42. In this way, the carriage41is configured to move the ejection heads20in the moving direction Ds.

As illustrated inFIG.3, each of the ejection heads20includes drive elements25. The drive elements25may be piezoelectric elements, heating elements, electrostatic actuators, and the like. The drive elements25are provided for respective nozzles27in the ejection head20and are configured to apply pressure to ink to eject the ink from the corresponding nozzles27.

The printing device1further includes a display device14, an input device15, and a control device50. The control device50is an example of the controller. The control device50includes an interface51, an arithmetic unit52, and a storage unit53. The interface51is configured to receive image data and other various data from an external device200. The external device200may be a computer, a camera, a communication network, a storage medium, a display, a printer, or the like. The image data is raster data and the like representing an image to be printed on the print medium W. The image data includes information on printing conditions such as the type of print medium W and the like. The control device50may be configured as a standalone device, or a plurality of devices in a distributed arrangement. In the latter case, the devices may operate the printing device1in cooperation with each other.

The storage unit53is memory that the arithmetic unit52can access. The storage unit53includes RAM and ROM. The RAM temporarily stores various data, including data received from the external device200, such as image data, and data converted by the arithmetic unit52. The ROM stores a printing program, prescribed data, and the like for performing various data processes. The printing program need not necessarily be stored in the storage unit53, and may be stored in an external storage medium such as a CD-ROM that is accessible by the arithmetic unit52.

The arithmetic unit52includes at least one of circuits, including a processor such as a Central Processing Unit (CPU), an integrated circuit such as an Application-Specific Integrated Circuit (ASIC), and the like. By executing the printing program, the arithmetic unit52controls the components of the printing device1to implement a printing operation and other various operations.

The display device14is a display, for example. In accordance with instructions from the control device50, the display device14displays images represented by image data, preview images PV described later, and the like. Note that the display device14may not be able to display images (uncalibrated images represented by image data) or preview images PV that are exactly the same as when printed on print media W with the ejection heads20. In this specification, the description “the display device14displays images represented by image data, and preview images PV” means not only that the display device14displays images and preview images PV that are exactly the same as when printed on print media W with the ejection heads20but also that the display device14displays images and preview images PV that are substantially the same as when printed on print media W with the ejection heads20. The input device15is configured of buttons and the like, for example, that the user operates. Alternatively, the input device15may be a touchscreen integrated with the display device14.

The control device50is electrically connected to the conveying motor32of the conveying device30via a conveyance drive circuit33for controlling the drive of the conveying motor32. Accordingly, the control device50is configured to control conveyance of the print medium W using the conveying device30. The control device50is also electrically connected to the scanning motor43of the scanning device40via a scan drive circuit46for controlling the drive of the scanning motor43. Accordingly, the control device50is configured to control movement of the ejection heads20using the scanning device40. The control device50is further electrically connected to the drive elements25via an ejection head drive circuit26. The control device50is configured to output control signals for the drive elements25to the ejection head drive circuit26, and the ejection head drive circuit26is configured to generate and output drive signals to the drive elements25on the basis of the control signals. When driven according to the drive signals, the drive elements25eject ink from the corresponding nozzles27.

In the printing device1having the above configuration, the control device50is configured to acquire image data and execute a printing operation on the basis of this image data. During this printing operation, the control device50controls the ejection heads20to eject ink onto the print medium W therefrom while moving the ejection heads20in the moving direction Ds in a printing path. Next, the control device50conveys the print medium W forward. The printing device1repeatedly alternates between a printing path and a conveying operation in this way to print an image on the print medium W based on the image data.

Below, color calibration according to the printing device1of the present embodiment will be described while referring to the accompanying drawings.

FIG.4illustrates an example of an image represented by image data that is displayed on the display device14.FIG.5illustrates the position of a first red color value f1, the position of a second red color value f2, and a printing color gamut PG in the L*a*b* color space CS. Note that the first red color value f1denotes the color value of a first red color and the second red color value f2denotes the color value of a second red color.

The control device50receives image data transmitted from the external device200. The image data includes color values. For example, the color value is represented by an RGB value in the RGB color space, i.e., as color coordinates in a device-dependent color space. The RGB value is constituted by a red component value, a green component value, and a blue component value, each of which represents one of a possible 256 gradations ranging from 0 to 255. The RGB value expresses a single color by the combination of these three component values.

The control device50acquires an image color gamut, which is a specific area of a predetermined color space that is occupied by the color values included in the image data. In this case, the control device50obtains the image color gamut by converting the RGB values in the image data to Lab values on the basis of predetermined correlations between RGB values and Lab values. Lab values are color values in the device-independent L*a*b* color space CS ofFIG.5expressed by Cartesian coordinates, with L representing lightness and a and b representing hue and saturation.

Next, the control device50displays on the display device14an image PI represented by the image data (image data having RGB values), as illustrated inFIG.4. In this example, the image PI includes an apple image PI1having the first red color, and a bell pepper image PI2having the second red color, which is different from the first red color. To distinguish between them, the first and second red colors are rendered in different grayscale brightnesses inFIG.4. This same display method is used inFIGS.6,7,9,10,11,13, and14described later.

When the image PI is displayed on the display device14, the user operates the input device15to specify one of the apple image PI1and bell pepper image PI2. For example, the user can specify the image on which the user wishes to focus. More specifically, the user specifies the image using a pointer14a(inFIG.4, the apple image PI1is pointed to by the pointer14a), and thus a color pointed to by the pointer14ais specified by the user (inFIG.4, the first red color in the apple image PI1is specified by the user).

The control device50receives information on the first red color, which is a color in the image color gamut and has been specified by the user (hereinafter sometimes referred to as the “specified color” or “user-specified color”). In the present embodiment, the first red color is an example of the first color.

Next, the control device50acquires a printing color gamut PG, which is a specific area of the L*a*b* color space CS that is occupied by color values that the ejection heads20can print using ink in the basic colors. The color values for the basic colors are expressed by CMYK values, for example, which are color coordinates in the device-dependent CMYK color space. A CMYK value is constituted by a cyan component value, a magenta component value, a yellow component value, and a black component value, each of which represents one value from a prescribed range of gradations, for example. The CMYK value expresses a single color by the combination of these four component values. The L*a*b* color space CS is an example of the predetermined color space.

Next, on the basis of information regarding whether the user-specified first red color is present in the printing color gamut PG and whether the second red color is present in the printing color gamut PG, the control device50executes two or more gamut mapping process (color compression processes) with different methods (i.e., two or more different gamut mapping processes) on the received image data. In this embodiment, the second red color is an example of the second color. The gamut mapping processes performed by the control device50will be described later.

The basic colors in the present embodiment are as follows. The basic colors are colors that the printing device1can print. The basic colors include the individual colors of ink provided in the printing device1and colors formed by combining at least two of the individual colors of ink. For example, when the printing device1is provided with ink in the colors cyan, magenta, yellow, and black, the basic colors are colors including at least one of these four colors. The basic colors include the individual ink colors cyan, magenta, yellow, and black, as well as mixtures of two or more of these colors. The color values for the basic colors are stored in the storage unit53in advance and are expressed in CMYK values, for example.

After the user selects an image from among the preview images PV, the control device50controls the ejection heads20to print an image corresponding to the selected preview image. In other words, the user can view the preview images PV corresponding to the results of the gamut mapping processes prior to printing and can select any one of the preview images PV that the user wishes to print.

Here, the gamut mapping processes executed by the control device50and the preview images PV obtained through these processes will be described in detail.

As described above, the control device50executes the gamut mapping processes on the basis of information indicating whether the user-specified first red color exists within the printing color gamut PG and whether the second red color exists within the printing color gamut PG. Below, a description will be given for a case in which the first red color value f1exists in the printing color gamut PG but the second red color value f2does not exist in the printing color gamut PG (the case ofFIG.5) and a case in which neither the first red color value f1nor the second red color value f2exists in a printing color gamut PGa different from the printing color gamut PG (the case ofFIG.8).

As described above, the control device50determines whether the first red color value f1exists in the printing color gamut PG and whether the second red color value f2exists in the printing color gamut PG. When the first red color value f1is in the printing color gamut PG but the second red color value f2is not, as illustrated inFIG.5, the control device50executes the following first and second gamut mapping processes. The first gamut mapping process is an example of the first process. The second gamut mapping process is an example of the second process.

In the first gamut mapping process, the control device50generates image data by maintaining (leaving) the first red color value f1as is and replacing (converting) the second red color value f2with (into) a color value in the printing color gamut PG. More specifically, the control device50generates image data by maintaining (leaving) the color values of the colors included in the apple image PI1as they are and replacing (converting) the color values of the colors included in the bell pepper image PI2with (into) the color values of colors in the printing color gamut PG.

In this case, the control device50replaces the second red color value f2with the color value of a color in the printing color gamut PG that approximates the second red color. The color value of a color that approximates the second red color denotes the color value in the printing color gamut PG that is closest in distance to the second red color value f2. For example, the color value of a color that approximates the second red color may be the color value at the point where the printing color gamut PG intersects a perpendicular line drawn from the position of the second red color value f2to the printing color gamut PG. This perpendicular line may be the line connecting the position of the second red color value f2to the printing color gamut PG with the shortest distance. Moreover, in the first gamut mapping process, the same color conversion (the same color replacement) as that performed on the first red color value f1in the first gamut mapping process is performed on each of the color values of the remaining colors included in the apple image PI1(i.e., the specified image) by the control device50. That is, the color values of the remaining colors included in the apple image PI1(i.e., the specified image) are also left unchanged, i.e., are maintained as they are. Furthermore, in the first gamut mapping process, the same color conversion (the same color replacement) as that performed on the second red color value f2in the first gamut mapping process is performed on each of the color values of the remaining colors included in the bell pepper image PI2by the control device50.

As illustrated inFIG.6, the control device50displays on the display device14a first preview image PV1represented by the image data generated in the first gamut mapping process. The control device50also displays the first red color (the specified color) in a display area14bof the display device14. Note that the display area14bhas been omitted fromFIG.7and subsequent drawings.

The first preview image PV1includes an apple preview image PV1ahaving the first red color, and a bell pepper preview image PV1bhaving a third red color, which differs from the second red color. That is, the color values of the apple preview image PV1aare the same as the color values of the apple image PI1since the first red color value f1and the remaining colors in the apple image PI1have been left unchanged in the first gamut mapping process. This ensures high reproducibility of the apple image PI1in the apple preview image PV1a. In contrast, the bell pepper preview image PV1bobtained in the first gamut mapping process has reduced reproducibility and loss of gradations (i.e., loss of tonality, such as loss of surface irregularities). To facilitate understanding,FIG.6andFIG.9described later exaggerate the states of the bell pepper preview images PV1band PV3b, omitting all lines depicting surface irregularities, but some lines depicting surface irregularities may remain. The third red color is an example of the replacement color.

As illustrated inFIG.6, the display device14is provided with two display areas14sfor displaying color differences. The control device50displays the color difference between the first red color before the first gamut mapping process and the first red color after the first gamut mapping process (i.e., a color resulting from the first gamut mapping process on the first red color) in one display area14sand displays the color difference between the second red color before the first gamut mapping process and the third red color after the first gamut mapping process (i.e., a color resulting from the first gamut mapping process on the second red color) in the other display area14s. This enables the user to recognize each color difference resulting from the first gamut mapping process. While these color differences are displayed as numbers in the display areas14sin this embodiment, the color differences may be displayed as shades of colors or the like.

In the second gamut mapping process, on the other hand, the control device50generates image data by replacing both the first red color and second red color with colors in the printing color gamut PG so that tonality (tonal range) is maintained between the first red color and the second red color. More specifically, the control device50generates image data by replacing (converting) the color values of the colors included in the apple image PI1and the color values of the colors included in the bell pepper image PI2with (into) the color values of colors in the printing color gamut PG so that tonality (tonal range) is maintained between an apple image (i.e., the colors included in the apple image) resulting from the second gamut mapping process on the apple image PI1and a bell pepper image (i.e., the colors included in the bell pepper image) resulting from the second gamut mapping process on the bell pepper image PI2.

In this example, the control device50replaces the first red color value f1with the color value of a color in the printing color gamut PG that approximates the first red color and replaces the second red color value f2with the color value of a color in the printing color gamut PG that approximates the second red color. Moreover, in the second gamut mapping process, the same color conversion (the same color replacement) as that performed on the first red color value f1in the second gamut mapping process is performed on each of the color values of the remaining colors included in the apple image PI1(i.e., the specified image) by the control device50. Furthermore, in the second gamut mapping process, the same color conversion (the same color replacement) as that performed on the second red color value f2in the second gamut mapping process is performed on each of the color values of the remaining colors included in the bell pepper image PI2by the control device50. The above term “tonality” will be described later.

As illustrated inFIG.7, the control device50displays on the display device14a second preview image PV2represented by the image data generated in the second gamut mapping process. The second preview image PV2in the example ofFIG.7includes an apple preview image PV2ahaving a fourth red color that differs from the first red color, and a bell pepper preview image PV2bhaving a fifth red color that differs from both the second and third red colors. The fourth red color and the fifth red color are colors resulting from the second gamut mapping process on the first red color and the second red color, respectively. The second gamut mapping process can reproduce surface irregularities in the bell pepper preview image PV2b(i.e., clipping does not occur to surface irregularities) by ensuring tonality (gradation) of the bell pepper preview image PV2bwhile sacrificing some reproducibility of the apple preview image PV2aand bell pepper preview image PV2b. The fourth red color is an example of the replacement color. The fifth red color is an example of the replacement color.

The control device50displays the color difference between the first red color before the second gamut mapping process and the fourth red color after the second gamut mapping process (i.e., a color resulting from the second gamut mapping process on the first red color) in one display area14sand displays the color difference between the second red color before the second gamut mapping process and the fifth red color after the second gamut mapping process (i.e., a color resulting from the second gamut mapping process on the second red color) in the other display area14s. As a result, the user can recognize the color differences resulting from the second gamut mapping process.

Here, the term “tonality” will be described using the above first and second gamut mapping processes as an example. In this description, L will denote the distance within the L*a*b* color space CS between a predetermined reference point and the position of the color value of the first red color. L1will denote the distance within the L*a*b* color space CS between the predetermined reference point and the position of the color value of a color resulting from the first gamut mapping process on the first red color. L2will denote the distance within the L*a*b* color space CS between the predetermined reference point and the position of the color value of a color resulting from the second gamut mapping process on the first red color. I will denote the distance within the L*a*b* color space CS between the predetermined reference point and the position of the color value of the second red color. I1will denote the distance within the L*a*b* color space CS between the predetermined reference point and the position of the color value of a color resulting from the first gamut mapping process on the second red color.12will denote the distance within the L*a*b* color space CS between the predetermined reference point and the position of the color value of a color resulting from the second gamut mapping process on the second red color. In the present embodiment, the predetermined reference point is the origin of the L*a*b* color space CS (i.e., the point with L*=50, a*=0, b*=0). However, the predetermined reference point need not necessarily be the origin of the L*a*b* color space CS but can be determined as appropriate.

Since the first red color value (the color value of the first red color) is preserved (maintained) in the first gamut mapping process, the distance L prior to processing becomes the distance L1(=L) after processing. Further, since the second red color value (the color value of the second red color) is converted to the third red color value (the color value of the third red color) in the first gamut mapping process, the distance I prior to processing becomes a distance I1(≠I) after processing. Therefore, L1/L=1, but I1/I≠1. Accordingly, (L1/L)≠(I1/I). Thus, tonality between the first red color and second red color is considered not maintained when (L1/L)≠(I1/I) is true, i.e., when the ratio of the distance L1to the distance L is not equal to the ratio of the distance I1to the distance I.

In this case, as described above, the same conversion as that performed on the first red color in the first gamut mapping process is performed on each of the remaining colors in the apple image PI1, and the same conversion as that performed on the second red color in the first gamut mapping process is performed on each of the remaining colors in the bell pepper image PI2. That is, the remaining colors in the apple image PI1are also converted (replaced) using the conversion ratio L1/L (=1), i.e., with the same conversion ratio as that applied to the conversion (the replacement) of the first red color, and the remaining colors in the bell pepper image PI2are also converted (replaced) using the conversion ratio I1/I (≠1), i.e., with the same conversion ratio as that applied to the conversion (the replacement) of the second red color. Accordingly, tonality (tonal range) is considered not maintained between an apple image (i.e., the colors included in the apple image) resulting from the first gamut mapping process on the apple image PI1and a bell pepper image (i.e., the colors included in the bell pepper image) resulting from the first gamut mapping process on the bell pepper image PI2. Note that the conversion (replacement) of a color using the conversion ratio L1/L (=1) denotes that the color is maintained as it is.

On the other hand, since the color value for the first red color is not maintained and the first red color is converted to the fourth red color in the second gamut mapping process, the distance L prior to processing becomes a distance L2(≠L) after processing. Further, since the second red color is converted to the fifth red color in the second gamut mapping process, the distance I prior to processing becomes a distance I2(≠I) after processing. In the second gamut mapping process, the first red color and second red color are converted to respective replacement colors that satisfy the expression (L2/L)=(I2/I). Thus, tonality between the first red color and second red color is considered maintained when (L2/L)=(I2/I) is satisfied, i.e., when the ratio of the distance L2to the distance L is equivalent to the ratio of the distance12to the distance I.

In this case, as described above, the same conversion as that performed on the first red color in the second gamut mapping process is performed on each of the remaining colors in the apple image PI1, and the same conversion as that performed on the second red color in the second gamut mapping process is performed on each of the remaining colors in the bell pepper image PI2. That is, the remaining colors in the apple image PI1are also converted (replaced) using the conversion ratio L2/L (=I2/I), i.e., with the same conversion ratio as that applied to the conversion (the replacement) of the first red color, and the remaining colors in the bell pepper image PI2are also converted (replaced) using the conversion ratio I2/I (=L2/L), i.e., with the same conversion ratio as that applied to the conversion (the replacement) of the second red color. Accordingly, tonality (tonal range) is considered maintained between an apple image (i.e., the colors included in the apple image) resulting from the second gamut mapping process on the apple image PI1and a bell pepper image (i.e., the colors included in the bell pepper image) resulting from the second gamut mapping process on the bell pepper image PI2.

Next, gamut mapping processes will be described for a case in which neither the first red color value f1nor the second red color value f2exists in the printing color gamut PGa.FIG.8illustrates the position of the first red color value f1, the position of the second red color value f2, the printing color gamut PGa in the L*a*b* color space CS. The printing color gamut PGa inFIG.8differs from the printing color gamut PG inFIG.5.

The control device50first determines whether the first red color value f1exists in the printing color gamut PGa and whether the second red color value f2is present in the printing color gamut PGa. When neither the first red color value f1nor the second red color value f2is present in the printing color gamut PGa, as in the example ofFIG.8, the control device50executes the following third gamut mapping process and fourth gamut mapping process. The third gamut mapping process is an example of the third process. The fourth gamut mapping process is an example of the fourth process.

In the third gamut mapping process, the control device50generates image data by replacing (converting) both the first red color value f1and the second red color value f2with (into) color values in the printing color gamut PGa while giving priority to approximating the first red color over the second red color. More specifically, the control device50generates image data by replacing (converting) both the color values of the colors included in the apple image PI1and the color values of the colors included in the bell pepper image PI2with (into) the color values of colors in the printing color gamut PGa while giving priority to approximating the colors included in the apple image PI1over the colors included in the bell pepper image PI2.

In this case, the control device50replaces the first red color value f1with the color value of a color in the printing color gamut PGa that approximates the first red color and replaces the second red color value f2with the color value of a color in the printing color gamut PGa that approximates the second red color. For example, giving priority to approximating the first red color signifies that the first and second red colors are replaced so that the relationship ΔE1<ΔE2is satisfied. Here, ΔE1denotes the color difference between the first red color and the color replacing the first red color and ΔE2denotes the color difference between the second red color and the color replacing the second red color. Moreover, in the third gamut mapping process, the same color conversion (the same color replacement) as that performed on the first red color value f1in the third gamut mapping process is performed on each of the color values of the remaining colors included in the apple image PI1(i.e., the specified image) by the control device50. Furthermore, in the third gamut mapping process, the same color conversion (the same color replacement) as that performed on the second red color value f2in the third gamut mapping process is performed on each of the color values of the remaining colors included in the bell pepper image PI2by the control device50.

As shown inFIG.9, the control device50displays on the display device14a third preview image PV3represented by the image data generated in the third gamut mapping process. The third preview image PV3in the example ofFIG.9includes an apple preview image PV3ahaving a sixth red color that differs from the first red color, and a bell pepper preview image PV3bhaving a seventh red color that differs from the second red color. Thus, according to the third gamut mapping process, the apple preview image PV3ahas reduced reproducibility but maintains gradations (tonality) while the bell pepper preview image PV3bhas reduced reproducibility and loss of gradations. The sixth red color is an example of the replacement color. The seventh red color is an example of the replacement color.

As shown inFIG.9, the control device50displays the color difference between the first red color before the third gamut mapping process and the sixth red color after the third gamut mapping process (i.e., a color resulting from the third gamut mapping process on the first red color) in one display area14sand displays the color difference between the second red color before the third gamut mapping process and the seventh red color after the third gamut mapping process (i.e., a color resulting from the third gamut mapping process on the second red color) in the other display area14s. As a result, the user can recognize each color difference resulting from the third gamut mapping process.

In the fourth gamut mapping process, on the other hand, the control device50generates image data by replacing (converting) the first red color value f1and the second red color value f2with (into) colors in the printing color gamut PGa to maintain tonality (tonal range) between the first red color and second red color. More specifically, the control device50generates image data by replacing (converting) the color values of the colors included in the apple image PI1and the color values of the colors included in the bell pepper image PI2with (into) the color values of colors in the printing color gamut PGa so that tonality (tonal range) is maintained between an apple image (i.e., the colors included in the apple image) resulting from the fourth gamut mapping process on the apple image PI1and a bell pepper image (i.e., the colors included in the bell pepper image) resulting from the fourth gamut mapping process on the bell pepper image PI2.

In this case, the control device50replaces the first red color value f1with the color value of a color in the printing color gamut PGa that approximates the first red color and replaces the second red color value f2with the color value of a color in the printing color gamut PGa that approximates the second red color. Moreover, in the fourth gamut mapping process, the same color conversion (the same color replacement) as that performed on the first red color value f1in the fourth gamut mapping process is performed on each of the color values of the remaining colors included in the apple image PI1(i.e., the specified image) by the control device50. Furthermore, in the fourth gamut mapping process, the same color conversion (the same color replacement) as that performed on the second red color value f2in the fourth gamut mapping process is performed on each of the color values of the remaining colors included in the bell pepper image PI2by the control device50.

The fourth gamut mapping process includes a perceptual rendering intent process and a relative rendering intent process. Since the perceptual and relative rendering intent processes are both well-known methods, a description of these methods will be omitted.

As shown inFIG.10, the control device50displays on the display device14a perceptual preview image PV40represented by image data generated in the perceptual rendering intent process as part of a fourth preview image PV4obtained in the fourth gamut mapping process. The perceptual preview image PV40includes an apple preview image PV40ahaving an eighth red color that differs from the first red color, and a bell pepper preview image PV40bhaving a ninth red color that differs from the second red color. Through the perceptual rendering intent process, which is one example of the fourth gamut mapping process, reproducibility of the apple image PI1is lower than in the third gamut mapping process, but a loss of surface irregularities (a loss of gradations) can be suppressed by maintaining tonality in the bell pepper preview image PV40b. The eighth red color is an example of the replacement color. The ninth red color is an example of the replacement color.

As shown inFIG.10, the control device50displays the color difference between the first red color before the perceptual rendering intent process and the eighth red color after the perceptual rendering intent process (i.e., a color resulting from the perceptual rendering intent process on the first red color) in one of the display areas14s. Further, the control device50displays the color difference between the second red color before the perceptual rendering intent process and the ninth red color after the perceptual rendering intent process (i.e., a color resulting from the perceptual rendering intent process on the second red color) in the other display area14s. As a result, the user can recognize each color difference resulting from the perceptual rendering intent process. Here, the color difference between the first red color before the perceptual rendering intent process and the eighth red color after the perceptual rendering intent process is greater than the color difference between the first red color before the third gamut mapping process and the sixth red color after the third gamut mapping process.

As shown inFIG.11, the control device50further displays on the display device14a relative preview image PV41represented by image data generated in the relative rendering intent process as part of the fourth preview image PV4. The relative preview image PV41includes an apple preview image PV41ahaving a tenth red color that differs from the first red color, and a bell pepper preview image PV41bhaving an eleventh red color that differs from the second red color. The tenth red color is an example of the replacement color. The eleventh red color is an example of the replacement color.

As shown inFIG.11, the control device50displays the color difference between the first red color before the relative rendering intent process and the tenth red color after the relative rendering intent process (i.e., a color resulting from the relative rendering intent process on the first red color) in one of the display areas14s. Further, the control device50displays the color difference between the second red color before the relative rendering intent process and the eleventh red color after the relative rendering intent process (i.e., a color resulting from the relative rendering intent process on the second red color) in the other display area14s. As a result, the user can recognize each color difference resulting from the relative rendering intent process. Here, the color difference between the first red color before the relative rendering intent process and the tenth red color after the relative rendering intent process is greater than the color difference between the first red color before the third gamut mapping process and the sixth red color after the third gamut mapping process.

According to the relative rendering intent process, which is an example of the fourth gamut mapping process, the color difference between the first red color before the relative rendering intent process and the tenth red color after the relative rendering intent process can be made smaller than the color difference between the first red color before the perceptual rendering intent process and the eighth red color after the perceptual rendering intent process.

FIG.12is a flowchart showing steps in a printing method performed by the printing device1. The process according to this flowchart begins when the printing device1receives a print job including image data via the interface51. In S1ofFIG.12, the control device50acquires the image color gamut for the image data received from the external device200. In S2the control device50analyzes the image data. Specifically, in S2the control device50performs a process to determine whether each color value in the image color gamut of the image data, which is RGB data, falls in the printing color gamut.

In S3the control device50determines whether a specified color specified by the user (the first red color of the apple image PI1in this embodiment) has been received. When a specified color has been received (S3: YES), the control device50continues from the process in S4described below. However, when a specified color has not been received (S3: NO), in S6the control device50controls the ejection heads20to print an image represented by the image data without performing color calibration.

In S4the control device50determines whether the color value of the specified color is in the printing color gamut PG. When the color value of the specified color is within the printing color gamut PG (S4: YES), in S5the control device50determines whether the color value of another color (the second red color of the bell pepper image PI2in the present embodiment) exists in the printing color gamut PG. When the color value for the other color is within the printing color gamut PG (S5: YES), in S6the control device50controls the ejection heads20to print an image represented by the image data without performing color calibration.

However, when the color value for the other color is not in the printing color gamut PG (S5: NO), in S7the control device50executes the first gamut mapping process and second gamut mapping process described above. In S8the control device50displays the first preview image PV1and second preview image PV2on the display device14. Subsequently, the control device50prompts the user to input the preferred one of the first preview image PV1and second preview image PV2. In S9the control device50selects the first preview image PV1or second preview image PV2based on the user input and in S6controls the ejection heads20to print the selected preview image PV.

However, when the color value of the specified color is not within the printing color gamut PG (S4: NO), in S10the control device50executes the third gamut mapping process and fourth gamut mapping process described above. In S11the control device50displays the third preview image PV3and fourth preview image PV4(the perceptual preview image PV40and relative preview image PV41) on the display device14. Subsequently, the control device50prompts the user to input the preferred one from the third preview image PV3, the perceptual preview image PV40, and the relative preview image PV41. In S12the control device50selects the third preview image PV3, perceptual preview image PV40, or relative preview image PV41based on the user input and in S6controls the ejection heads20to print the selected preview image PV.

When the first red color value f1is present in the printing color gamut PG while the second red color value f2is not, the control device50may also execute the following process in combination with the first and second gamut mapping processes described above.FIG.13shows a preview image PV5for a case of printing an image on a print medium having a different type from the type of print medium W specified in the printing conditions.

The control device50acquires printing conditions that include the type of print medium W. When the first red color value f1is present in the printing color gamut PG while the second red color value f2is not, the control device50displays the preview image PV5for a case of printing an image represented by the image data on a different type of print medium (e.g., high-quality paper such as fine paper, woodfree paper, or the like) from the type of print medium W included in the printing conditions, as illustrated inFIG.13. Also, this process is executed in combination with the third and fourth gamut mapping processes described above.

The preview image PV5includes an apple preview image PV5ahaving a twelfth red color that differs from the first red color, and a bell pepper preview image PV5bhaving a thirteenth red color that differs from the second red color. As shown inFIG.13, the control device50displays the color difference between the first red color before processing and the twelfth red color after processing in one of the display areas14sand displays the color difference between the second red color before processing and the thirteenth red color after processing in the other display area14s. Printing an image on high-quality paper, as in this example can expand saturation and density (gradation range).

When the first red color value f1is present in the printing color gamut PG but the second red color value f2is not present in the printing color gamut PG, the control device50may also execute the following process in combination with the first and second gamut mapping processes described above.FIG.14shows a preview image PV6for a case in which an image represented by the image data is printed on a print medium W using ink in different colors from the basic colors.

Specifically, when the first red color value f1is in the printing color gamut PG but the second red color value f2is not, the control device50displays the preview image PV6shown inFIG.14for a case of printing an image represented by the image data on a print medium W using special colors of ink that differ from the basic colors. Also, this process is executed in combination with the first and second gamut mapping processes described above.

The preview image PV6includes an apple preview image PV6ahaving a fourteenth red color that is the same color as the first red color, and a bell pepper preview image PV6bhaving a fifteenth red color that is the same color as the second red color. As shown inFIG.14, the control device50displays the color difference between the first red color before processing and the fourteenth red color after processing in one of the display areas14sand displays the color difference between the second red color before processing and the fifteenth red color after processing in the other display area14s. This example can obtain an apple preview image PV6awith high reproducibility of the apple image PI1, and a bell pepper preview image PV6bwith high reproducibility of the bell pepper image PI2.

When the user has selected the preview image PV6, special color inks stored in the second tanks12binFIG.2described above are supplied from the second tanks12bto the second ejection heads22along the second channels13b. More specifically, the storage solution filling the second ejection heads22is purged from the second ejection heads22and replaced with the special color inks. Therefore, when a purge is executed to discharge storage solution from the nozzles of the second ejection heads22, the control device50determines that a process to introduce special color inks has been performed and that the second channels13bare filled with special color inks. The control device50prints patches on the print medium W for the color values in the preview image PV6selected by the user. Next, the control device50measures the colors of the patches printed on the print medium W with a colorimeter, such as a spectrophotometer, and stores the colorimetric values in the storage unit53in association with the color values of the corresponding patches. The control device50then creates a calibration profile for calibrating colors in an image being printed to target colors based on the above correlations and controls the ejection heads20to print an image corresponding to the preview image PV6on the print medium W on the basis of the calibration profile.

As described above, the printing device1according to the present embodiment displays on the display device14the preview images PV corresponding to the results of two or more gamut mapping processes with different methods. Thus, unlike the conventional method of printing an image after performing a uniform gamut mapping process, the method of the embodiment presents the user with preview images PV generated by two or more gamut mapping processes with different methods. The user can select a desired preview image to print from among the two or more preview images PV displayed. As this method allows the user to print a desired image, user satisfaction in printed images can be improved.

Further, the first gamut mapping process in the present embodiment can ensure high reproducibility of the apple image PI1in the apple preview image PV1a. As a result, the process can ensure high reproducibility of the user's specified color, i.e., the color with which the user is concerned, thereby increasing user satisfaction. With the second gamut mapping process, reproducibility of the apple preview image PV2arelative to the apple image PI1is lower than that in the first gamut mapping process, but the second gamut mapping process can suppress a loss of surface irregularities (a loss of gradations) in both the apple preview image PV2aand the bell pepper preview image PV2b.

Additionally, the third gamut mapping process in the present embodiment can ensure tonality in the apple preview image PV3ain exchange for reduced reproducibility. Thus, this method can ensure reproducibility and maintain tonality for the user-specified color, i.e., the color on which the user is focused, thereby increasing user satisfaction. Further, the perceptual rendering intent serving as one example of the fourth gamut mapping process has lower reproducibility of the apple image PI1than that of the third gamut mapping process but can suppress a loss of surface irregularities (a loss of gradations) in the bell pepper preview image PV40bby ensure tonality thereof. Further, the relative rendering intent serving as an example of the fourth gamut mapping process enables the color difference between the colors before and after the relative rendering intent process is performed to be made smaller than the color difference between the colors before and after the perceptual rendering intent process is performed. Thus, reproducibility is comparatively high when using the relative rendering intent.

In the present embodiment, the control device50displays the preview image PV5for a case of printing an image represented by the image data on a different type of print medium (e.g., fine paper) from the type of print medium W specified in the printing conditions. This enables the user to select the preview image PV5when the user wishes to expand saturation and density (gradation range) by printing the image on high-quality paper.

In the present embodiment, the control device50displays the preview image PV6for a case of printing an image represented by the image data on the print medium W using ink in special colors that differ from the basic colors. Thus, the user can select the preview image PV6when the user wishes to significantly enhance reproducibility by printing with special colors of ink.

Variations of the Embodiment

In the above embodiment, the preview image PV5is displayed together with the preview images PV produced in the first to fourth gamut mapping processes. However, the preview image PV5may simply be displayed alone. For example, when the first red color value f1is present in the printing color gamut PG while the second red color value f2is not, the control device50may display just the preview image PV5for a case of printing an image represented by the image data on a different type of print medium from the type of print medium W included in the printing conditions, as illustrated inFIG.13.

Similarly, the preview image PV6is displayed together with preview images PV produced through the first to fourth gamut mapping processes in the embodiment described above. However, the preview image PV6may simply be displayed alone. For example, when the first red color value f1is in the printing color gamut PG but the second red color value f2is not, the control device50may display just the preview image PV6for a case of printing an image represented by the image data on the print medium W using ink of special colors that differ from the basic colors, as illustrated inFIG.14.

While an inkjet printer serves as an example of the printing device1in the embodiment described above, the printing device1may be another printer, such as a laser printer or a thermal printer. A laser printer is provided with a printing unit. The printing unit of the laser printer includes an image carrier such as a photosensitive drum or a photosensitive belt, a charger that charges the image carrier through contact or non-contact, an exposure unit that forms an electrostatic latent image on the charged image carrier using a laser semiconductor or the like (known as “exposure”), a toner cartridge or developing cartridge that supplies toner to the image carrier on which an electrostatic latent image has been formed, a transfer unit such as a transfer roller or transfer belt that transfers the developed toner image from the image carrier directly to a print medium, and a fixing unit such as a fixing roller or fixing belt that thermally fixes the toner (the toner image) transferred onto the print medium. The laser printer is not limited to a direct tandem laser printer but may be an intermediate transfer laser printer. The intermediate transfer laser printer first transfers the developed toner image from the image carrier onto an intermediate transfer belt and then uses the transfer unit to transfer the toner image from the intermediate transfer belt onto the print medium. A thermal printer is provided with a printing unit. The printing unit of the thermal printer includes a thermal head, and an ink ribbon. The thermal head contacts the ink ribbon and transfers ink in the ink ribbon onto a print medium by causing the corresponding heating elements to generate heat.

In the embodiment described above, the preview images PV are displayed on the display device14of the printing device1, but the present disclosure is not limited to this configuration. For example, the preview images PV may be displayed on the display of a personal computer or other device that can communicate with the printing device1through cables or wirelessly.

In the embodiment described above, the perceptual rendering intent process and relative rendering intent process are used as examples of the fourth gamut mapping process, but the fourth gamut mapping process is not limited to these processes. Other processes such as an absolute rendering intent process may be executed as the fourth gamut mapping process.