Patent Publication Number: US-2011050772-A1

Title: Printing apparatus using plural color inks including white color ink and printing method thereof

Description:
Priority is claimed under 35 U.S.C. §119 to Japanese Application No. 2009-199217 filed on Aug. 31, 2009, Japanese Application No. 2009-281293 filed on Dec. 11, 2009, and Japanese Application No. 2010-058820 filed on Mar. 16, 2010, which are hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a printing apparatus using a plurality of color inks including a white color ink and a printing method thereof. 
     2. Related Art 
     Printing apparatuses which print using a white color ink in addition to color inks such as cyan, magenta, and yellow are known (For example, in JP-A-2002-38063). The printing apparatus which prints using a plurality of color inks including a white color ink can, for example, perform the treatment of the surface of a printing medium with the use of a white color ink and/or complementary color processing depending on the ground color to reproduce a color image without being influenced by the ground color of the printing medium. 
     There are some cases in which a transparent film is used as the printing medium when printing by using a plurality of color inks including a white color ink. For example, it is possible to use the transparent film like a white printing medium as the printing medium in a manner of forming a color image after forming a white image using a white color ink, or forming a white image after forming a color image on the transparent film. There are some cases in which a white protective layer (also can be called a “separator”) is detachably attached to the opposite side surface (back surface) of the print surface (front surface) of the transparent film serving as the printing medium, for the purpose of preventing scratches, for example. 
     For example, in the case of performing correction (calibration) during printing, color measurement of a printed image is performed. In the case of performing the color measurement of the white image during the printing using the transparent film, since it is impossible to detect a density difference in the white image by the color measurement in the state in which the white protective layer is attached to the transparent film, a complicated process, for example, including a step of peeling off the protective layer from the transparent film, a step of setting the transparent film on the black background, and then a step of measuring color of the white image is required. Furthermore, when peeling off the protective layer from the transparent film, there is a concern that the transparent film will be scratched. Therefore, there is a concern that the accuracy of the color measurement is lowered due to the scratches on the transparent film. 
     SUMMARY 
     An advantage of some aspects of the invention is to accomplish high accuracy and efficiency in color measurement of a white image formed by printing with the use of a plurality of color inks including a white color ink. 
     In order to solve at least part of the above problems, the invention can be realized in the following forms and applications. 
     Application 1 
     A printing apparatus, which prints on a transparent printing medium with a back surface to which a white protective layer is detachably attached by using a plurality of color inks including a white color ink, includes a head having a nozzle group which ejects ink, a control unit forming an image on the transparent printing medium by controlling the head, and a color measurement unit measuring color of an image formed on the transparent printing medium in the state in which the protective layer is attached to the transparent printing medium, in which the control unit controls the head such that a black image is formed on the transparent printing medium and a white image is formed on the formed black image in an overlapping manner in the case in which an object to be color-measured is a white image containing an image of a toned-white color which is an adjusted white color. 
     According to the printing apparatus, in the case in which the object to be color-measured is a white image, a black image is formed on the transparent printing medium, a white image is then formed on the formed black image in an overlapping manner, and the color measurement of the image formed on the transparent printing medium is performed in the state in which the protective film is attached to the transparent printing medium. Accordingly, it is possible to efficiently perform the color measurement of the white image without peeling off the protective film from the transparent printing medium and setting the transparent printing medium on the black background, prevent the transparent printing medium from getting scratched, inhibit influence of the scratches of the transparent printing medium on a color measurement value, and perform the color measurement of the white image with high accuracy. 
     Application 2 
     In the printing apparatus of Application 1, it is preferable that the control unit controls the head in a manner such that an image which is the object to be color-measured is directly formed on the transparent printing medium in the case in which the object to be color-measured is an image other than the white image. 
     According to the printing apparatus, the image which is the object to be color-measured is directly formed on the transparent printing medium in the case in which the object to be color-measured is an image other than the white image. Accordingly formation of the black image serving as the background is not needed. Therefore, it is possible to efficiently and highly accurately perform the color measurement of even an image which is other than the white image. 
     Application 3 
     In the printing apparatus of Application 1 or Application 2, it is preferable that the head includes a first nozzle group for forming a color image including a black image on the transparent printing medium and a second nozzle group for forming a white image on the transparent printing medium as the nozzle group, and the control unit controls the head in a manner such that, in the case in which the object to be color-measured is the white image, formation of the black image using the first nozzle group and formation of the white image using the second nozzle group are performed in parallel during at least one part of the period of the printing. 
     According to the printing apparatus, it is possible to perform in parallel formation of the black image on the transparent printing medium and formation of the white image on the formed black image. Therefore, it is possible to efficiently perform the color measurement of the white image formed by printing using a plurality of color inks including a white color ink. 
     Application 4 
     In the printing apparatus of any one out of Application 1 to Application 3 it is preferable that, in the case in which a plurality of black patches having the same density value are printed at a plurality of densities, a print density of the black image is set with a density of the black patches having the smallest variance in brightness values thereof among the plurality of black patches having the same density value. 
     According to the printing apparatus, the density of the black patches having the smallest variance in the brightness values among the plurality of black patches having the same density value is set as the print density of the black image. Accordingly, it is possible to appropriately perform the color measurement of the white image without variation. 
     Application 5 
     In the printing apparatus of Application 4, it is preferable that, in the case in which a print instruction of the white image is received, a single black patch having the density of which the variance in the brightness values is the smallest is printed, calibration is performed with respect to the single printed black patch, and the black image is printed using the density after the calibration. 
     According to the printing apparatus, the black image is printed using the density of the black patch after the calibration. Accordingly, it is possible to appropriately perform the color measurement of the white image on the basis of the black image having an accurate density characteristic. 
     Application 6 
     In the printing apparatus of Application 5, it is preferable that the black patch to be printed to perform the calibration is printed by bidirectional printing (Bi-D) and the black image is printed by unidirectional printing (Uni-D). 
     According to the printing apparatus, the black patch for performing the calibration is printed by the bidirectional printing (Bi-D). Accordingly, it is possible to print the black patch at fast speed. Further, since the black image is printed by the unidirectional printing (Uni-D), it is possible to secure a sufficient time to dry the black image and thus to prevent the black image from spreading into the white image when forming the white image on the black image in an overlapping manner. 
     Application 7 
     In the printing apparatus of any one out of Application 4 to Application 6, it is preferable that the black patch is printed using a downstream side nozzle in a printing medium transportation direction and the black image is printed using an upstream side nozzle in the printing medium transportation direction. 
     According to the printing apparatus, the black patch is printed using the downstream side nozzle and the black image is printed using the upstream side nozzle. Accordingly, the difference between frequencies in the use of the upstream side nozzle and the downstream side nozzle is small. As a result, the unevenness of color is suppressed. 
     Application 8 
     A printing method of printing on a transparent printing medium with a back surface to which a white protective layer is detachably attached, using a plurality of color inks including a white color ink, includes (a) forming an image on the transparent printing medium by controlling a head having a nozzle group which ejects ink, and (b) measuring color of an image formed on the transparent printing medium in the state in which the protective film is attached to the transparent printing medium, wherein in step (a), in the case in which an object to be color-measured is a white image containing an image of a toned-white color which is an adjusted white color, the head is controlled such that a black image is formed on the transparent printing medium and the white image is formed on the formed black image in an overlapping manner. 
     The invention can be realized in various embodiments, for example, a printing method and a printing apparatus, a printing control method and a printing control apparatus, a color measuring method and a color measuring apparatus, a correcting method of a printing apparatus, a printing system, a computer program for executing functions of these methods, apparatuses, and systems, a recording medium in which the computer program is recorded, and a data signal or the like embodied in a carrier wave along with the computer program or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is an explanatory view schematically showing the structure of a printing system according to one embodiment of the invention. 
         FIG. 2  is an explanatory view schematically showing the structure of a PC. 
         FIG. 3  is an explanatory view schematically showing the structure of a printer. 
         FIG. 4  is a block diagram functionally showing the structure of the PC. 
         FIG. 5  is a block diagram functionally showing the structure of the printer. 
         FIG. 6  is a flowchart showing the flow of correction processing according to another embodiment of the invention. 
         FIG. 7  is an explanatory view showing one example of an image to be printed for the correction processing. 
         FIG. 8A  is an explanatory view showing one example of an image to be printed for the correction processing. 
         FIG. 8B  is an explanatory view showing one example of an image to be printed for the correction processing. 
         FIG. 9A  is an explanatory view showing print order of a color image and a toned-white image. 
         FIG. 9B  is an explanatory view showing print order of the color image and the toned-white image. 
         FIG. 10  is a flowchart showing the flow of print processing according to a further embodiment of the invention. 
         FIG. 11  is a flowchart showing the flow of processing by a CPU which executes a printer driver. 
         FIG. 12  is a flowchart showing the flow of color conversion processing, ink color separation processing, and halftone processing for the toned-white image. 
         FIG. 13A  is an explanatory view partially showing an example of a look-up table for the toned-white image. 
         FIG. 13B  is an explanatory view partially showing another example of the look-up table for the toned-white image. 
         FIG. 14  is a flowchart showing the flow of color conversion processing, ink color separation processing, and halftone processing for a color image. 
         FIG. 15  is an explanatory view partially showing an example of a look-up table for the color image. 
         FIG. 16  is a flowchart showing the flow of command production processing. 
         FIG. 17A  is an explanatory view showing an example of a command created by command production processing. 
         FIG. 17B  is an explanatory view showing another example of the command created by the command production processing. 
         FIG. 18  is an explanatory view showing an example of the content of an ink code table. 
         FIG. 19  is a flowchart showing the flow of processing by the printer. 
         FIG. 20  is an explanatory view showing the detailed structure of a raster buffer and a head buffer. 
         FIG. 21A  is an explanatory view showing the structure of a print head of the printer. 
         FIG. 21B  is another explanatory view showing the structure of the print head of the printer. 
         FIG. 21C  is a further explanatory view showing the structure of the print head of the printer. 
         FIG. 22  is an explanatory showing an example of a patch sheet for specifying a density. 
         FIG. 23  is a flowchart showing the flow of processing of printing a patch sheet for specifying a density. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described in the following order; 
     A. Embodiment: 
     A-1. Structure of printing system:
 
A-2. Correction processing:
 
A-3. Print processing:
 
B. Modified example.
 
     A. EMBODIMENT 
     A-1. Structure of Printing System 
       FIG. 1  is an explanatory view schematically showing the structure of a printing system according to one embodiment of the invention. A printing system  10  of the embodiment includes a printer  100  and a personal computer (PC)  200 . The printer  100  is an ink jet type color printer for printing an image by forming ink dots on a printing medium by ink ejection. The PC  200  functions as a printing control apparatus for supplying print data to the printer  100  and controlling print operation of the printer  100 . The printer  100  and the PC  200  are connected to each other in wired or wireless manner so that information can be transmitted and received therebetween. In detail, according to the embodiment, the printer  100  and the PC  200  are connected to each other by a USB cable. In the embodiment, as the printing medium, a transparent film TF with a white protective layer (hereinafter, referred to as “separator SE”) detachably attached to the opposite side surface (back surface) other than the print surface (front surface) of the transparent film TF is used. 
     The printer  100  according the embodiment is a printer which prints using a total of seven color inks of cyan (C), magenta (M), yellow (Y), black (K), light cyan (Lc), light magenta (Lm), and white (W). The printing system  10  according to the embodiment can perform print processing in which a color image and a toned-white image are formed in parallel on the transparent film TF serving as the printing medium. That is, the printer  100  can print using the transparent film TF like a white printing medium as the printing medium by forming the color image on the toned-white image while forming the toned-white image, or forming the toned-white image on the color image while forming the color image on the transparent film TF. The transparent film TF on which the color image and the toned-white image are formed may be, for example, a film for packaging goods. 
     In the specification, the term “white” not only means substantial white which is a color of appearance of an object which reflects 100%, of all wavelengths of incident visible light but also refers to a color which can be called white in the common sense, for example, “white-tint.” That is, the term “white” means (1) a color within a color range in which a representative in a Lab system is around or inside a circle having a radius of 20 on a*b* plane and L* is 70 or more in the case in which color is measured in the condition of color measurement mode: spot color measurement, light source: D50, backing: black, and printing medium: transparent film, by using “eye-one Pro” which is a spectrophotometer manufactured by X-Rite corporation, (2) a color within a color range in which a representative in a Lab system is around or inside a circle having a radius of 20 on a*b* plane and L* is 70 or more in the case in which color is measured in the condition, measurement mode D502° viewing angle, SCF mode, and white background back, by using a spectrophotometer CM2022 which is a spectrophotometer manufactured by Minolta Corp., or (3) a color of an ink used as the background of an image as disclosed in JP-A-2004-306591, and the meaning of the term “white” is not limited to pure white but includes an ink color that can used as the background. 
     Further, in the specification, adjusting a white color (white) ink by mixing a predetermined amount of a color ink with the white color ink is referred to as “white-toning” and a white color produced by the white-toning (white which is toned) is called “toned-white”, and an image formed of the toned-white is called a “toned-white image.” However, the meaning of the term “toned-white” also includes a white color in which a zero amount of a color ink is mixed with the white color ink. That is, the term “toned-white” also includes a white color composed of only the white color ink. In a similar manner, the meaning of the term “toned-white image” includes a white image formed of only the white color ink. The meaning of the term “color image” includes an image formed of only a single color ink other than the white color (for example, a black image formed of only a black ink). 
       FIG. 2  is an explanatory view schematically showing the structure of a PC  200 . The PC  200  includes a CPU  210 , a ROM  220 , a RAM  230 , a USB interface (USB I/F)  240 , a network interface (N/W I/F)  250 , a display interface (display I/F)  260 , a serial interface (serial I/F)  270 , a hard disk drive (HDD)  280 , and a compact disk drive (CD drive)  290 . The components of the PC  200  are connected to each other via a bus. 
     The display interface  260  of the PC  200  is connected to a monitor MON serving as a display device. The serial interface  270  is connected to a keyboard KB and a mouse MOU serving as input devices. The structure of the PC  200  shown in  FIG. 2  is only an example. Therefore, the structure of the PC  200  can be transformed so as to omit some of the components of the above or include other components. 
       FIG. 3  is an explanatory view schematically showing the structure of a printer  100 . The printer  100  includes a CPU  110 , a ROM  120 , a RAM  130 , a head controller  140 , a print head  144 , a carriage controller (CR controller)  150 , a carriage motor (CR motor)  152 , a printing medium transportation controller (PF controller)  160 , a printing medium transportation motor (PF motor)  162 , a USB interface (USB I/F)  170 , a network interface (N/W I/F)  180 , a monitor  190  serving as a display unit, and an automatic spectrophotometer  192  for automatically measuring color of a print image. Components of the printer  100  are connected to each other via a bus. 
     The CPU  110  of the printer  100  functions as a control unit which controls operation of the entire printer  100  by executing a computer program stored in the ROM  120 . The print head  144  of the printer  100  is mounted on the carriage which is not shown. The carriage controller  150  moves the carriage in reciprocating manner in a predetermined direction by controlling the carriage motor  152 . With such control, the print head  144  reciprocates in the predetermined direction (main scanning direction) of the printing medium. That is, main scanning is performed. The printing medium transportation controller  160  performs sub-scanning in which the printing medium is transported in a direction (sub-scanning direction) which is orthogonal to the main scanning direction by controlling the printing medium transportation motor  162 . The print head  144  has a nozzle group (shown in  FIG. 21 ) which ejects ink, and the head controller  140  controls ejection of ink from the nozzle group by the print head  144  in association with the main scanning and sub-scanning operations. In such a manner, formation of an image on the printing medium (printing of an image) is realized. 
       FIG. 4  is a block diagram functionally showing the structure of the PC  200 . The ROM  220  (shown in  FIG. 2 ) of the PC  200  stores an application program AP and a printer driver  300  as computer programs executed by the CPU  210  therein. The application program AP is a program to set, produce, and edit an image (hereinafter, referred to as “printing object image PI”) which is an object to be printed on the transparent film TF serving as the printing medium. The CPU  210  realizes setting, producing, and editing of the printing object image PI by executing the application program AP. 
     The CPU  210  which executes the application program AP outputs color image data Cdata, toned-white image data WITdata, and print order specifying information SS to the printer driver  300  in response to a print execution instruction. The content of the data will be described below. 
     The printer driver  300  (shown in  FIG. 4 ) is a program for producing print data (print command) on the basis of image data or the like and performing print processing of the printing object image PI by controlling the printer  100  (shown in  FIG. 1 ) on the basis of the print data. The CPU  210  ( FIG. 2 ) realizes print control of the printing object image PI by the printer  100  by executing the printer driver  300 . 
     As shown in  FIG. 4 , the printer driver  300  includes a color image ink color separation processing module  310 , a color image halftone processing module  320 , a toned-white image color conversion module  340 , a toned-white image ink color separation processing module  350 , a toned-white image halftone processing module  360 , and a command producing module  370 . The HDD  280  ( FIG. 2 ) of the PC  200  stores a color image look-up table (LUT) LUTc, a color image halftone (HT) resource HTc, a tone-white image look-up table (LUT) LUTw, a toned-white image halftone (HT) resource HTw, and an ink code table ICT therein. The printer driver  300  and the above-mentioned modules execute the processing referring to the information. The contents or information of each module will be described below. 
       FIG. 5  is a block diagram functionally showing the structure of the printer  100 . The ROM  120  (shown in  FIG. 3 ) of the printer  100  stores a command processing module  112  which is a computer program executed by the CPU  110  therein. Although it is described later, the CPU  110  realizes processing of the command received from the PC  200  by executing the command processing module  112 . The RAM  130  ( FIG. 3 ) of the printer  100  has a raster buffer  132 . The raster buffer  132  includes two regions, a color image raster buffer  132   c  and a toned-white image raster buffer  132   w . The head controller  140  ( FIG. 3 ) of the printer  100  has a head buffer  142 . The head buffer  142  includes an upstream head buffer  142   u  and a downstream head buffer  1421 . Functions and detailed structures of the programs and buffers are described later. 
     A-2. Correction Processing 
       FIG. 6  is a flowchart showing the flow of correction processing in the printing system  10  according to the embodiment. The correction processing is processing of printing the printing object image PI for the correction processing on the basis of predetermined image data, performing the color measurement of the printed image, and adjusting (correcting) the printer  100  on the basis of the result of comparison between the image data and the measured color value. Hereinafter, the correction processing in which the white color ink is an object to be adjusted will be described. 
     In Step S 10  ( FIG. 6 ), print processing of the printing object image PI used for the correction processing is performed.  FIG. 7  and  FIGS. 8A and 8B  are explanatory views showing examples of the printing object image PI used for the correction processing.  FIG. 7  schematically shows a state in which the printing object image PI is formed on the surface (print surface) of the transparent film TF, which is the opposite surface of the surface (back surface) to which the separator SE is attached. As shown in  FIG. 7 , when performing the correction processing to adjust the white color ink as an object, a black image is formed as a color image Ic and then a white image is formed on the black image as a toned-white image Iw in an overlapping manner. In the embodiment, the toned-white image Iw is composed of a plurality of image regions (Iw 1  to Iw 6 ) having different densities. 
       FIGS. 8A and 8B  show image data used for printing the printing object image PI for the correction processing. In detail,  FIG. 8A  shows color image data Cdata used for forming a black image serving as the color image Ic, and  FIG. 8B  shows toned-white image data WITdata used for forming a white image serving as the toned-white image Iw. The color image data Cdata and the toned-white image data WITdata are prepared beforehand, and stored in the hard disk drive  280  of the PC  200 . 
     In the embodiment, the color image data Cdata is represented by a color specification value of CMYK color specification system. The toned-white image data WITdata is represented by a combination of a density value T and a color specification value (L* value (hereinafter, simply referred to as “L value”), a* value (hereinafter, simply referred to as “a value”), and b* value (hereinafter, simply referred to as “b value”)) in L*a*b color specification system. T value is in relation with an ink amount per a unit area upon printing the toned-white image Iw. 
     The color image data Cdata and the toned-white image data WITdata are not needed to be prepared beforehand but may be produced at the time of performing print processing. For example, values representing colors of corresponding regions (Iw 1  to Iw 6 ) of the toned white image Iw are acquired via the user interface, the toned-white image data WITdata may be produced on the basis of the acquired values. The color image data Cdata is produced in a manner such that the color image Ic is associated with the regions of the toned-white image Iw of the produced toned-white image data WITdata. 
     As described below, the printing system  10  of the embodiment can form the color image Ic and the toned-white image Iw such that they overlap each other.  FIGS. 9A and 9B  are explanatory views showing the print order of the color image Ic and the toned-white image Iw.  FIG. 9A  shows the order in which the toned-white image Iw is formed on the transparent film TF and then the color image Ic is formed on the toned-white image Iw. In the specification, this print order is referred to as “white-color printing” or “W-C printing.” In the W-C printing shown in  FIG. 9A , a viewer can see a print piece from the upside of the figure (see an arrow in the figure).  FIG. 9B  shows the print order in which the color image Ic is formed on the transparent film TF, and then the toned-white image Iw is formed on the color image Ic. In the specification, this print order is referred to as “color-white printing” or “C-W printing.” In the C-W printing shown in  FIG. 9B , a viewer sees the print piece from the underside (see an arrow in the figure). 
     In the correction processing in which the white color ink is an object to be adjusted, as shown in  FIG. 7 , the C-W printing is performed. The print order in the print processing is specified by print order specifying information SS (shown in  FIG. 4 ). 
     Upon the print processing (Step S 10  in  FIG. 6 ), the color image data Cdata, the toned-white image data WITdata and the print order specifying information SS are supplied to the printer driver  300  from the application program AP (see  FIG. 4 ), a command is produced on the basis of the data and information within the printer driver  300  and sent to the printer  100 , and the printing is performed on the basis of the command in the printer  100 . The detailed content of the print processing will be described in a following chapter with the heading of “A-3. Print processing” later. 
     In Step S 20  (shown in  FIG. 6 ), the color measurement of the printed image formed by the print processing of Step S 10  is performed. As described above, the printer  100  according to the embodiment has an automatic spectrophotometer  192  and the color measurement of the printed image can be automatically performed by the automatic spectrophotometer  192 . The color measurement of the image regions (Iw 1  to Iw 6 ) which constitute the toned-white image Iw (shown in  FIG. 7 ) is performed in the state in which the separator SE is attached to the transparent film TF. Color measurement values are values corresponding to the toned-white image data WITdata, that is, L value, a value, b value, and T value. 
     In Step S 30  ( FIG. 6 ), the correction of the printer  100  is executed. In the correction of the printer  100 , adjustment of, for example, an ink ejection amount or the like of the printer  100  is performed on the basis of the result of comparison between the toned-white image data WITdata and the color measurement values. 
     As described above, the printing system  10  of the embodiment prints on the print surface of the transparent film TF to which the white protective layer (separator SE) on the back side is detachably attached, using the plurality of color inks including the white color ink. In the correction processing, in which the white color ink is an object to be adjusted, in the printing system  10 , the black image (color image Ic) is formed on the transparent film TF, the white image (toned-white image Iw) is formed on the black image in an overlapping manner, and then automatic color measurement of the white image is performed. While the color measurement of the white image is performed in the state in which the separator SE of a white color is attached to the transparent film TF, however, in the embodiment, since the black image is formed under the white image, it does not happen that the density difference of the white images cannot be detected. Therefore, the color measurement can be performed without problems. Accordingly, in the embodiment, it is possible to efficiently realize the color measurement of the white image without peeling off the separator SE from the transparent film TF or setting the transparent film TF on the black background. In the embodiment, since it is not necessary to peel off the separator SE from the transparent film TF in the printer  100 , it is possible to prevent the transparent film TF from being scratched. Moreover, it is possible to prevent the scratches on the transparent film TF from negatively influencing the color measurement values, and to realize the color measurement of the white image with high accuracy. 
     A-3. Print Processing 
     Hereinafter, details of the printing process (Step S 10  of  FIG. 6 ) will be described. The description is not given to only the limited partial print processing relating to the correction processing but to the overall print processing but to the overall print processing of printing a general print object PI. When performing the correction processing, a correction processing image shown in  FIG. 7  is used as the printing object image PI and the print processing described below is performed. 
       FIG. 10  is a flowchart showing the flow of the print processing in the printing system  10  according to the embodiment. The print processing of the embodiment is processing of forming the color image and the toned-white image in parallel on the transparent film serving as the printing medium, and producing a print piece on which the color image and the toned-white image are formed thereon. 
     In Step S 110  (shown in  FIG. 10 ), the CPU  210  (shown in  FIG. 2 ) executing the application program AP (shown in  FIG. 4 ) receives a print execution instruction from a user. The CPU  210  outputs the color image data Cdata, the toned-white image data WITdata, and the print order specifying information SS to the printer driver  300  upon receiving the print execution instruction (see  FIG. 4 ). In the embodiment, the color image data Cdata is data specifying the color image Ic in the printing object image PI with CMYK values, and the toned-white image data WITdata is data specifying the toned-white image Iw in the printing object image PI with Lab values or T values. The print order specifying information SS is data specifying the print order of the color image and the toned-white image in the overlapping portion of the color image and the toned-white image. 
     Pixel values of the toned-white image data WITdata may be specified via the user interface or preset values may be used as the pixel values. 
     In Step S 120  of the print processing (shown in  FIG. 10 ), processing by the CPU  210  which executes the printer driver  300  (shown in  FIG. 4 ) is executed.  FIG. 11  is a flowchart showing the flow of processing by the CPU  210  which executes the printer driver  300 . In Step S 210 , the CPU  210  receives the color image data Cdata, the toned-white image data WITdata, and the print order specifying information SS output from the application program AP (see  FIG. 4 ). 
     In Step S 230  in the processing ( FIG. 11 ) by the printer driver  300 , the printer driver  300  executes the color conversion processing, ink color separation processing, and halftone processing for the toned-white image.  FIG. 12  is a flowchart showing the flow of the color conversion processing, the ink color separation processing, and the halftone processing for the toned-white image. In Step S 410 , a toned-white image color conversion module  340  ( FIG. 4 ) converts the Lab values of the toned-white image data WITdata to the CMYK values. The color conversion is performed referring to a toned-white image look-up table LUTw ( FIG. 4 ). 
       FIGS. 13A and 13B  are explanatory views partially showing examples of the toned-white image look-up table LUTw.  FIG. 13A  shows the toned-white image look-up table LUTw 1  which is referenced when conducting the color conversion from the Lab values to the CMYK values. As shown in  FIG. 13A , a corresponding relation between the preset Lab values and the CMYK values is specified in the toned-white image look-up table LUTw 1 . In the toned-white image look-up table LUTw 1 , each gradation value of CMYK is specified with a value in the range from 0 to 100. The toned-white image color conversion module  340  converts the Lab values to the CMYK values referring to the toned-white image look-up table LUTw 1 . 
     In Step S 420  ( FIG. 12 ), a toned-white image ink color separation processing module  350  ( FIG. 4 ) performs ink color separation processing of converting the combination of each of the CMYK values determined in Step S 410  and each of the T values of the toned-white image data WITdata to a gradation value by an ink color. As described above, the printer  100  of the embodiment prints using total seven color inks of cyan (C), magenta (M), yellow (Y), black (K), light cyan (Lc), light magenta (Lm), and white (W). In the ink color separation processing, the combination of each of the CMYK values and each of the T values is converted to the gradation value for each of seven ink colors. The ink color separation processing is performed referring to the toned-white image look-up table LUTw ( FIG. 4 ).  FIG. 13B  shows a toned-white image look-up table LUTw 2  which is referenced when the combinations of the CMYK values and the T values are converted to the gradation values of respective ink colors. As shown in  FIG. 13B , in the toned-white image look-up table LUTw 2 , a corresponding relation between the combinations of the respective preset CMYK values and the respective T values and the gradation values of the respective ink colors are specified. In the toned-white image look-up table LUTw 2 , the gradation value of each color is specified with a value in the range from 0 to 255. The toned-white image ink separation processing module  350  converts the combination of each of the CMYK values and each of the T values to the gradation value for each of the ink colors referring to the toned-white image look-up table LUTw 2 . 
     As shown in  FIG. 13(   b ), in the embodiment, for the white-toning (adjusting a white color by mixing color inks excluding a white color ink with the white color ink), four color inks of yellow (Y), black (K), light cyan (Lc), and light magenta (Lm) among six color inks are used but two color inks of cyan (C) and magenta (M) are not used. That is, a dark color ink out of two kinds of inks (a light color ink and a dark color ink)—of one color is not used for the white-toning. 
     In Step S 430  ( FIG. 12 ), the toned-white image ink separation processing module  350  ( FIG. 4 ) takes out single pixel data from the toned-white image data. In Step S 440 , the toned-white image ink separation processing module  350  judges a value of the taken data of the single pixel. In the case in which it is judged such that the value of the pixel is not zero (Step S 440 : No), the toned-white image ink separation processing module  350  stores gradation values of respective ink colors determined in Step S 420  (Step S 450 ). In the case in which it is judged such that the value of the pixel is zero (Step S 440 : Yes), the processing of Step S 450  is skipped. 
     The processing from Step S 430  to Step S 450  of  FIG. 12  is repeatedly performed until the processing for all of the pixels in the toned-white image data is finished (see step S 460 ). In the case in which the processing for all of the pixels is finished (Step S 460 : Yes), the toned-white image halftone processing module  360  ( FIG. 4 ) takes out gradation values of respective ink colors of a single pixel (Step S 470 ) and performs binarization processing (halftone processing) referring to dither patterns of respective ink colors (Step S 480 ). The binarization processing is performed referring to preset toned-white image halftone resource HTw ( FIG. 4 ). The toned-white image halftone resource HTw may be set with a priority on filling of dots in the toned-white image. The binarization processing is repeatedly performed until the binarization for all of the ink colors is finished (see Step S 490 ). The processing from Step S 470  to Step S 490  is repeatedly performed until the processing for all of the pixels is finished (see Step S 492 ). 
     By the color conversion processing, the ink color separation processing, and the halftone processing for the toned-white image shown in  FIG. 12 , toned-white image dot data which specifies ON/OFF of a dot for each ink color for respective pixels is generated when forming the toned-white image. 
     In Step S 240  in the processing ( FIG. 11 ) by the printer driver  300 , the printer driver  300  executes the color conversion processing, the ink color separation processing, and the halftone processing for the color image.  FIG. 14  is a flowchart showing the flow of the color conversion processing, the ink color separation processing, and the halftone processing for the color image. In Step S 510 , a color image ink separation processing module  310  ( FIG. 4 ) takes out data of data of a single pixel data in the color image data. In Step S 520 , the color image ink color separation module  310  performs the ink color separation processing of converting the taken single pixel data (CMYK values) to the gradation values of respective ink colors. As described above, the printer  100  of the embodiment prints by using total seven color inks: cyan (C), magenta (M), yellow (Y), black (K), light cyan (Lc), light magenta (Lm), and white (W). Accordingly, in the ink color separation processing, the CMYK values are converted to the gradation values for respective seven ink colors. The ink color separation processing is performed referring to the color image look-up table LUTc ( FIG. 4 ). Here, as for a density value, the density value after the black patch is printed and the calibration is performed is used. The printing of the black patch and the calibration processing will be described below in detail. 
       FIG. 15  is an explanatory view partially showing an example of the color image look-up table LUTc. As shown in  FIG. 15 , in the color image look-up table LUTc, corresponding relation between the preset CMYK value and the gradation value for each of ink colors is specified. In the color image look-up table LUTc, the respective gradation values of CMYK are specified with values in the range from 0 to 100. The gradation value of each of ink colors is specified with a value in the range from 0 to 255. The color image ink separation processing module  310  converts the CMYK values to the gradation values of respective ink colors referring to the color image look-up table LUTc. As shown in  FIG. 15 , in the embodiment, six ink colors except white are used to form the color image. That is, the white color ink is not used. 
     The processing of Step S 510  and Step S 520  of  FIG. 14  is repeatedly performed until the processing for all of the pixels of the color image data is finished (see Step S 530 ). In the case in which the processing for all of the pixels is finished (Step S 530 : Yes), a color image halftone processing module  320  ( FIG. 4 ) takes out gradation values of respective ink colors for a single pixel (Step S 540 ), and performs the binarization processing (halftone processing) referring to the dither patterns of respective ink colors (Step S 550 ). The binarization processing is executed referring to the preset color image halftone resource HTc ( FIG. 4 ). Alternatively, the color image halftone resource HTc may be set with a priority on suppression of granularity. The binarization processing is repeatedly executed until the processing for all of the ink colors is finished (see Step S 560 ). The processing from Step S 540  to Step S 560  is repeatedly executed until the processing for all of the pixels is finished (see Step S 570 ). 
     By the color conversion processing, the ink color separation processing, and the halftone processing for the color image which is shown in  FIG. 14 , color image dot data which specifies ON/OFF of dots of respective ink colors for each of pixels when forming the color image is produced. 
     In Step S 250  in the processing ( FIG. 11 ) by the printer driver  300 , a command producing module  370  ( FIG. 4 ) of the printer drive  300  performs command production processing.  FIG. 16  is a flowchart showing the flow of the command production processing. 
     In Step S 610  of the command production processing ( FIG. 16 ), a command producing module  370  ( FIG. 4 ) produces a print order specifying command on the basis of the print order specifying information SS output from the application program AP.  FIGS. 17A and 17B  are explanatory views showing examples of the command produced by the command production processing. As shown in  FIG. 17A , the print order specifying command includes an identifier representing a command head, an identifier showing that the command is a print order specifying command, a command length (2 byte), and specification of print order. In the specification of print order, for example, the value “0” represents the C-W printing (print order in which the color image Ic is formed first and then the toned-white image Iw is formed on the color image Ic) and the value “1” represents the W-C printing (print order in which the toned-white image Iw is formed first and then the color image Ic is formed on the toned-white image Iw). The command producing module  370  determines the print order by referring to the print order specifying information SS and produces the print order specifying command which specifies the determined print order. 
     In Step S 620  ( FIG. 16 ), the command producing module  370  ( FIG. 4 ) produces a vertical position specifying command on the basis of the color image dot data received from the color image halftone processing module  320  and the toned-white image dot data received from the toned-white image halftone processing module  360 . The vertical position specifying command is a command of specifying a starting position of the image in the vertical direction (Y direction). The vertical position specifying command is produced as a common command for all of inks. 
     Next, the command producing module  370  ( FIG. 4 ) produces a raster command corresponding to the color image through the processing from Step S 630  ( FIG. 16 ) to Step S 670 . In Step S 630 , the command producing module  370  produces a horizontal position specifying command for a selected single color ink on the basis of the color image dot data. The horizontal position specifying command is a command of specifying starting position of the image in the horizontal direction (X direction) for a single ink color upon forming the color image. The command producing module  370  sets a proper image starting position by referring to the color image dot data for a single ink color and produces the horizontal position specifying command. 
     In Step S 640  ( FIG. 16 ), the command producing module  370  ( FIG. 4 ) takes out dot data of a single raster for the selected single ink color from the color image dot data. In Step S 650 , the command producing module  370  searches an ink code by referring to an ink code table ICT.  FIG. 18  is an explanatory view showing an example of the content of the ink code table ICT. As shown in  FIG. 18 , in the embodiment, each ink color is assigned with a unique abbreviated ink name and an ink code. In the embodiment, a single ink color is assigned with two different abbreviated ink names and two ink codes, one for the color image and the other for the toned-white image. That is, the abbreviated ink name and the ink code uniquely correspond to the combination of a single ink color among plural ink colors and any one out of the color image and the toned-white image. For example, cyan is assigned with the abbreviated ink name “C” for the color image and the ink code “01H”, and also with the abbreviated ink name “WC” for the toned-white image and the ink code “81H.” In the same manner, white is assigned with the abbreviated ink name “IW” for the color image and the ink code “40H” and with the abbreviated ink name “WC” for the toned-white image and the ink code “C0H.” In Step S 650 , the command producing module  370  searches the ink code for the color image in the ink code table ICT. 
     In Step S 660  ( FIG. 16 ), the command producing module  370  ( FIG. 4 ) produces the raster command on the basis of the taken dot data for the single raster part and the searched ink code.  FIG. 17B  shows an example of the raster command. As shown in  FIG. 17B , the raster command includes an identifier representing a command head, an identifier showing that the command is the raster command, an ink code, an identifier showing whether the data is compressed or not, the number of bits for a single pixel, a X-direction length (2 bytes), a Y-direction length (2 bytes) and raster data (dot data). 
     The processing from Step S 630  to Step S 660  of the command producing processing ( FIG. 16 ) is repeatedly performed until the processing for all of the ink colors used in formation of the color image is finished. That is, in the case in which there is any remaining ink color which has not yet undergone the processing (Step S 670 : No), one ink color which has not yet undergone the processing is selected, and the processing from Step S 630  to Step S 660  is performed for the selected ink color. If the processing for all of the ink colors is finished (Step S 670 : Yes), as for a single raster, production of the raster commands corresponding to the respective ink colors used in formation of the color image is completed. 
     Next, the command producing module  370  ( FIG. 4 ) produces the raster commands corresponding to the toned-white image through-out the processing from Step S 680  ( FIG. 16 ) to Step S 720 . In Step S 680 , the command producing module  370  produces a horizontal position specifying command for the selected single ink color on the basis of the toned-white image dot data. The horizontal position specifying command is a command specifying starting position of the image in the horizontal direction (X direction) for a single ink color upon forming the toned-white image. The command producing module  370  sets proper image starting position by referring to the toned-white image dot data for a single ink color and produces the horizontal position specifying command. 
     In Step S 690  ( FIG. 16 ), the command producing module  370  ( FIG. 4 ) takes out the dot data of a single raster for a selected single ink color from the toned-white image dot data. In Step S 700 , the command producing module  370  searches the ink code by referring to the ink code table ICT. The command producing module  370  searches the ink code for the toned-white image from the ink code table ICT ( FIG. 18 ). 
     In Step S 710  ( FIG. 16 ), the command producing module  370  ( FIG. 4 ) produces the raster commands (see  FIG. 17B ) on the basis of the taken single raster dot data and the searched ink code. The processing from Step S 680  to Step S 710  of the command producing processing is repeatedly performed until the processing for all of the ink colors used in formation of the toned-white image is finished. That is, in the case in which there is any remaining ink color which has not yet undergone the processing (Step S 720 : No), a single ink color which has not yet undergone the processing is selected, and the processing from Step S 680  to Step S 710  is performed for the selected single color. If the processing for all of the ink colors is finished (Step S 720 : Yes), as for a single raster, production of the raster commands corresponding to the respective ink colors used in formation of the toned-white image is completed. 
     The processing from Step S 620  to Step S 720  of the command producing processing ( FIG. 16 ) is repeatedly performed until the processing for all of the rasters of the printing object image PI is completed. That is, in the case in which there is any remaining raster which have not yet undergone the processing (Step S 730 : No), a raster which has not yet undergone the processing (a following raster of the raster which has undergone the previous processing) is selected, and the processing from Step S 620  to Step S 720  is performed for the selected raster. The processing for all of the rasters is finished (Step S 730 : Yes), as for the entire raster, production of the commands corresponding to the respective ink colors used in formation of the color image and the toned-white image is completed. 
     In Step S 260  in the processing ( FIG. 11 ) by the printer driver  300 , the printer driver  300  sends the print order specifying command, the vertical position specifying command, the horizontal position specifying command, and the raster command produced in Step S 250  to the printer  100 . Thus the processing by the printer driver  300  is completed. 
     In Step S 130  of the print processing ( FIG. 10 ), the processing by the printer  100  is performed.  FIG. 19  shows a flowchart showing the flow of the processing by the printer  100 . In Step S 810 , the CPU  110  ( FIG. 3 ) which executes the command processing module  112  ( FIG. 5 ) of the printer  100  receives the command sent from the printer driver  300  of the PC  200 . The CPU  110  identifies the kind of the received command (Step S 820 ), and executes the processing according to the kind of command. In the case in which the received command is the print order specifying command, the CPU  110  stores the information showing the print order specified by the print order specifying command in the RAM  130  (Step S 830 ). On the other hand, in the case in which the received command is the horizontal position specifying command, the CPU  110  updates horizontal-direction printing starting position X (Step S 840 ). 
     In the case in which the received command is the raster command, the CPU  110  ( FIG. 3 ) executing the command processing module  112  ( FIG. 5 ) stores the raster data (dot data) contained in the raster command in the raster buffer  132  ( FIG. 5 ) for each ink code (Step S 850 ).  FIG. 20  is an explanatory view showing the detailed structure of the raster buffer and the head buffer. The upper portion of  FIG. 20  shows the color image raster buffer  132   c , and the middle portion shows the toned-white image raster buffer  132   w . As shown in  FIG. 20 , the raster buffer  132  is divided into regions so as to correspond to each ink code (see  FIG. 18 ). That is, the color image raster buffer  132   c  is structured to be a group of regions corresponding to each ink code for the color image. The toned-white image raster buffer  132   w  is also structured to be a group of regions corresponding to each ink code for the toned-white image. The X-direction size of each region of the raster buffer  132  matches the size of the image, and the Y-direction size is not shorter than a half of the height of the print head  144 . The raster buffer  132  has a Y-direction raster buffer pointer showing how far the raster data is received. 
     The lower portion of  FIG. 20  shows the head buffer  142  ( FIG. 5 ). As shown in  FIG. 20 , the head buffer  142  is divided into regions so as to correspond to seven ink colors. That is, the head buffer  142  is structured to be a group of a cyan (C, WC) region, a magenta (M, WM) region, a yellow (Y, WY) region, a black (K, WK) region, a light cyan (Lc, WLc) region, a light magenta (Lm, WLm) region, and a white (IW, W) region. The X-direction size of each region of the head buffer  142  corresponds to the scanning distance of the carriage, and the Y-direction size corresponds to the number of nozzles constituting the nozzle column  146  of the print head  144 . Each of the regions of the heads buffer  142  which correspond to the ink colors is divided into an upstream head buffer  142   u  and a downstream head buffer  142   l.    
       FIGS. 21A ,  21 B,  21 C are explanatory views showing the structure of the print head  144  of the printer  100 . As shown in  FIGS. 21A and 21B , the print head  144  is provided with nozzle columns  146  corresponding to seven ink colors, respectively. The nozzle column  146  is formed so as to extend in the Y direction (print medium transportation direction). As shown in  FIG. 21C , each of the nozzle columns  146  is composed of 32 nozzle groups arranged in the printing medium transportation direction. Among the nozzle groups constituting the nozzle column  146 , the nozzle groups positioned within the upstream side half in the printing medium transportation direction (from the first nozzle (nozzle  1 ) to the sixteenth nozzle (nozzle  16 )) are upstream nozzle groups, and the nozzle groups positioned within the downstream side half in the printing medium transportation direction (seventeenth nozzle (nozzle  17 ) to thirty second nozzle (nozzle  32 ) are called downstream nozzle groups. 
     As shown in  FIG. 21A , when performing the W-C printing, formation of the toned-white image is performed using the upstream side nozzle groups of each nozzle column  146  of the print head  144 , and formation of the color image is performed using the downstream nozzle groups. As shown in  FIG. 21B , when performing the C-W printing, the color image is formed using the upstream nozzle groups of each nozzle column  146  of the print head  144  and formation of the toned-white image is performed using the downstream side nozzle groups. When performing the W-C printing, the upstream nozzle groups of each nozzle column  146  of the print head  144  corresponds to the second nozzle group in the invention, and the downstream nozzle groups correspond to the first nozzle group in the invention. Conversely, when performing the C-W printing, the upstream nozzle groups of each nozzle column  146  of the print head  144  correspond to first nozzle group of the invention and the downstream nozzle groups correspond to the second nozzle group. 
     As shown in  FIG. 20 , the upstream head buffer  142   u  is the head buffer  142  corresponding to an upstream side portion (upstream nozzle groups) of the print head  144  in the printing medium transportation direction, and the downstream head buffer  142   l  is the head buffer  142  corresponding to a downstream side portion (downstream nozzle groups) of the print head  144  in the printing medium transportation direction. 
     In Step S 850  of  FIG. 19 , the CPU  110  ( FIG. 3 ) refers to the ink code contained in the received raster command, and stores the raster data in the position which is specified by the raster buffer pointer of the raster buffer  132  which corresponds to the ink code. Accordingly, the CPU  110  can sort the raster data into the proper regions of the raster buffer  132  without awareness of whether the raster command is a command for the color image or a command for the toned-white image. 
     The CPU  110  ( FIG. 3 ) executing the command processing module  112  ( FIG. 5 ) updates the printing start position Y in the vertical direction in the case in which the received command is the vertical position specifying command (Step S 860 ). Next, the CPU  110  judges whether the raster buffer  132  corresponding to a half of the height of the print head  144  ( FIG. 5 ) is full or not (that is, whether the raster data is stored) (Step S 870 ). In the case in which it is not full (Step S 870 : No), the CPU  110  updates the raster buffer pointer of the raster buffer  132  (Step S 880 ). 
     If the above-described processing is repeated and the raster data is stored in the raster buffer  132  which corresponds to the half of the height of the print head  144 , it is judged such that the portion of the raster buffer  132  which corresponds to the half of the height of the print head  144  is full (Step S 870 : Yes). At this time, the CPU  110  ( FIG. 3 ) judges whether the print order is the C-W printing or the W-C printing on the basis of the information showing the print order stored in the RAM  130  (Step S 880 ). In the case in which the print order is the C-W printing (Step S 880 : Yes), the CPU  110  transmits the raster data from the color image raster buffer  132   c  to the upstream head buffer  142   u  ( FIG. 5 ) and the raster data from the toned-white image raster buffer  132   w  to the downstream head buffer  142   l  ( FIG. 5 ) (Step S 890 ).  FIG. 20  shows operation such that, in the case in which the print order is the C-W printing, the raster data is transmitted from the color image raster buffer  132   c  to the upstream head buffer  142   u , and the raster data is transmitted from the toned-white image raster buffer  132   w  to the downstream head buffer  142   l . With this operation, formation of the color image is performed using the upstream nozzle groups of each nozzle column  146  of the print head  144 , and reference of the C-W printing ( FIG. 21B ) in which formation of the toned-white image is performed using the downstream nozzle groups is prepared. Further, since physical print positions on paper between the upstream nozzle groups and the downstream nozzle groups are different from each other, in the case of transmitting the raster data from the raster buffer  132 , the transmission start position of the data in the raster buffer is determined taking the difference of the printing positions between the upstream nozzle groups and the downstream nozzle groups into consideration. 
     On the other hand, in the case in which the print order is the W-C printing (Step S 880 : No), the CPU  110  transmits the raster data from the color image raster buffer  132   c  to the downstream head buffer  142   l  ( FIG. 5 ), and the raster data from the toned-white image raster buffer  132   w  to the upstream head buffer  142   u  (Step S 900 ). With this operation, formation of the toned-white image is performed using the upstream nozzle groups of each nozzle column  146  of the print head  144 , and reference for the W-C printing ( FIG. 21A ) in which formation of the color image is performed using the downstream nozzle groups is prepared. 
     Next, the CPU  110  ( FIG. 3 ) transports (sub-scans) the printing medium PM to the position Y of the head by controlling the printing medium sending controller  160  and the printing medium sending motor  162  (Step S 910 ), makes the print head  144  move to the printing start position X by controlling the carriage controller  150  and the carriage motor  152  (Step S 920 ), and performs printing as much as the height of the print head  144  by performing the main-scanning. (Step S 930 ). For this instance, in the W-C printing (see  FIG. 21A ), formation of the toned-white image by the upstream nozzle groups (see  FIG. 21C ) of each nozzle column  146  of the print head  144  and formation of the color image by the downstream nozzle groups are performed in parallel. Further, in the C-W printing (see  FIG. 21B ), formation of the color image by the upstream nozzle groups of each nozzle column  146  of the print head  144  and formation of the toned-white image by the downstream nozzle groups are performed in parallel. 
     Next, the CPU  110  ( FIG. 3 ) clears the raster buffer pointer of the raster buffer  132  (Step S 940 ), judges whether the print processing of the entire printing object image PI is completed (Step S 950 ), and the processing from Step S 810  to Step S 940  is repeatedly performed until it is judged such that the print processing is completed. If it is judged such that the print processing is completed, the print processing ( FIG. 10 ) is finished. 
     Hereinafter, details about the processing of black patch print and calibration for acquiring a density value of a black image serving as the color image (the density value being used in Step S 420  of  FIG. 12  is described. The processing of the black patch print and calibration is performed in the case in which the CPU  210  ( FIG. 2 ) executing the application program AP ( FIG. 4 ) receives the print execution instruction from the user (Step S 110  of  FIG. 10 ). 
     In the first place, a patch sheet for specifying the density of the black patch is printed by the printer  100  to specify the density of the black patch.  FIG. 22  is an explanatory view showing an example of the patch sheet for specifying the density. In the example of  FIG. 22 , four black patch groups P 1 , P 2 , P 3 , and P 4  are printed on the print surface of the patch sheet S. Each of the black patch groups is provided with three black patches having the same density and arranged at intervals. The black patch groups P 1 , P 2 , P 3 , and P 4  have different densities and are arranged in the order such that their densities gradually decrease from the highest to the lowest. 
       FIG. 23  is a flowchart showing the flow of the processing of printing the patch sheet for the density specification.  FIG. 23  shows the flow of printing two black patch groups P 1  and P 2  arranged in a single row. In Step S 310 , a density value of the first black patch group P 1  as density  1  which is preset in the PC  200 . 
     In Step S 320 , in the PC  200 , the color conversion processing, the ink color separation processing, and the halftone processing with respect to the patch image data stored in, for example, the hard disk drive  280  are performed on the basis of the density value set in Step S 310 . Then, a single black patch which has passed through out the halftone processing is printed in the printer  100 . Here, in the printer  100 , the black patch is printed using the downstream side nozzle groups shown in the structure of the print head  144  of  FIG. 21 . For this instance, the black patch is printed by bidirectional main-scanning (Bi-D) of the print head  144 . 
     In Step S 330 , it is judged whether three black patches constituting the black patch group P 1  are printed. If the case in which three black patches are not printed (Step S 330 : No), the processing of Step S 320  is repeatedly performed until all of the three black patches are printed. In the case in which all of the three black patches are printed (Step S 330 : Yes), in the PC  200 , a density value of the next black patch group P 2  is set with density  2  which is predetermined (Step S 340 ). Then, returning to Step S 320 , the print processing of the black patch is repeatedly performed with the density value set in Step S 340 . 
     After the patch sheet S for the density specification is printed out from the printer  100 , the user views and checks the patch sheet on which the black patch groups P 1 , P 2 , P 3  and P 4  are printed, and makes an input of the black patch group having the smallest variance in brightness values of three black patches among the black patch groups with the use of a keyboard KB or a mouse MOU of the PC  200 . With this, the set density value of the input black patch group is specified in particular as the density value of the black patch for the calibration processing. Alternatively, the density value of the black patch for the calibration processing may be specified in a manner such that variance of the L values of the black patches is automatically measured through the color measurement by an automatic spectrophotometer  192  of the printer  100  instead of the visual checking of the patch sheet by the user. 
     After specifying the density value of the black patch, a single black patch is printed with the specified density value in the printer  100 . In the printer  100 , the black patch is printed using the downstream nozzle groups of the print head  144 . For this instance, the black patch is printed by the bidirectional main-scanning (Bi-D) of the print head  144 . 
     Next, the calibration processing for the printed single black patch is performed. The density value of the black patch after the calibration is used as the density value of the black image. The black image to be printed is printed by using the upstream nozzle groups of the print head  144  because the print order is the C-W printing. For this instance, the black image is printed by the unidirectional main-scanning (Uni-D) of the print head  144 . 
     B. MODIFIED EXAMPLE 
     The invention is not limited to the above-described examples and embodiments but can be implemented in various forms within the scope which is not departing from the spirit of the invention. For example, the following modifications may be allowable. 
     B1. Modified Example 1 
     The printing object image PI ( FIG. 7 ) for the correction processing in the above embodiment is just only an example, and the printing object image PI for the correction processing can be diversely modified. For example, a toned-white image Iw composed of regions having a single density may be used as the printing object image PI. 
     B2. Modified Example 2 
     In the above embodiment, when printing the printing object image PI for the correction processing, the nozzle group of the head is divided into two groups, upstream and downstream groups, and the color image Ic (black image) and the toned-white image Iw (white image) are formed in parallel. However, it is not absolutely necessary to form the color image Ic and the toned-white image Iw in parallel. That is, it is allowable that the color image Ic is formed on the transparent film TF first and then the toned-white image Iw is formed on the formed color image Ic by rewinding the transparent film TF. 
     B3. Modified Example 3 
     Although, in the above embodiment, description is given of the correction processing in which the white color ink is an object to be adjusted, correction processing in which another color ink is an object to be adjusted may be performed. However, in the case of the correction processing in which another color ink is an object to be adjusted, the printing object image PI may be directly formed on the print surface of the transparent film TF upon printing the printing object image PI for the correction processing. That is, it is unlikely that the black image is formed between the transparent film TF and the object image to be color-measured. This is because it is possible to accomplish the color measurement of the print image with good accuracy even without formation of the black image in the case of the correction processing in which another color ink is an object to be adjusted. 
     B4. Modified Example 4 
     The structure of the printing system  10  of the above-described embodiment is provided just as an example and therefore the structure of the printing system  10  can be diversely modified. For example, although the printer  100  according to the above embodiment is a printer which prints using seven color inks: cyan, magenta, yellow, black, light cyan, light magenta, and white, it is sufficient that the printer is a printer  100  which prints using plural color inks including a white color ink. For example, the printer  100  may be a printer which prints using 5 color inks: cyan, magenta, yellow, black, and white. 
     Further, according to the above embodiment, although only six color inks but the whit ink are used in formation of the color image, ink colors used in the formation of the color image can be arbitrarily set depending on ink colors which can be used in the printer  100 . For example, it is allowable that the white color ink is used in the formation of the color image. 
     Still further, according to the above embodiment, although five color inks of white, yellow, black, light cyan, and light magenta are used but two ink colors of cyan and magenta are not used in formation of the toned-white image, the ink colors used in formation of the toned-white image can be arbitrarily set depending on the ink colors which can be used in the printer  100 . For example, only four color inks of white, yellow, light cyan, and light magenta may be used or seven color inks of white, yellow, black, light cyan, light magenta, cyan, and magenta may be used to form the toned-white image. 
     Yet still further, according to the embodiment, the printer  100  is a printer which prints by reciprocating (main-scanning) the carriage on which the print head  144  is mounted. However, the invention can be applied to print processing performed by a line printer in which there is no reciprocal movement of the carriage. 
     Furthermore, according to the embodiment, the printer driver  300  is installed in the PC  200 , and the printer  100  prints by receiving the commands from the printer driver  300  of the PC  200  (see  FIG. 4 ). However, it is also possible that the printer  100  has the same function as the printer driver  300  including the toned-white image specifying module and the UI control module which is not shown in the figures and the printer  100  prints by receiving the color image data Cdata, the toned-white image data WITdata, and the print order specifying information SS from the application program AP of the PC  200 . Alternatively, the printer  100  may further have the same function as the application program AP, so production of the color image data Cdata, the toned-white image data WITdata, and the print order specifying information SS, and the print processing may be performed in the printer  100 . 
     Still furthermore, according to the above embodiment, the contents of the toned-white image look-up table LUTw and the color image look-up table LUTc are examples, and these contents are, for example, empirically set depending on the composition of inks used in the printer  100 . The contents diversely vary according to the contents (color space in use) of the data output from the application program AP and ink colors used in the printer  100 . Similarly, the contents of the color conversion processing and the ink color separation processing in which the tables are used diversely vary. 
     Yet furthermore, according to the embodiment, the halftone processing is performed referring to the dither pattern by the color image halftone processing module  320  and/or the toned-white image halftone processing module  360  ( FIG. 4 ). However, the halftone processing may be performed by other methods such as a random dithering method (color error diffusion). Moreover, in the case in which the printer  100  can form dots having a plurality of sizes for each ink color, multi-value processing which determines ON/OFF and sizes of the dots may be conducted instead of the binarization which determines ON/OFF of the dots by the halftone processing. 
     Moreover, in the above embodiment, the structures of the print order specifying command, the raster command and the content of the ink code table ICT are provided just as examples and are diversely modified. In the above embodiment, the ink codes uniquely correspond to the respective combinations of one of the plural ink colors and any one of the color image and the toned-white image. However, it is not absolutely necessary to set the ink codes in such a manner. If the ink codes are set in that manner, the CPU  110  of the printer  100  can perform the command processing according to the ink code contained in the raster command without awareness of whether the raster command is for the color image or for the toned-white image. 
     In the above embodiment, a portion of the structure realized by hardware may be changed to software. Conversely, a portion of the structure realized by software may be changed to hardware. 
     In the case in which a portion of the function or the entire function of the invention is realized by software, the software (computer program) can be provided in the form in which it is stored in a computer readable recording medium. In the invention, the term “computer readable recording medium” includes internal storage devices in a computer such as various RAMs and ROMs and external storage devices fixed to a computer such as a hard disk as well as unlimitedly includes mobile recording media such as a flexible disk and a CD-ROM. 
     The printer  100  according to the above embodiment can perform the print processing in which the color image (which includes a color image formed using a white color ink) is formed. In such a case, the nozzle columns  146  of the print head  144  are not divided into upstream and downstream groups, the printing is performed using the entire nozzle columns  146 . That is, the printer  100  may perform the printing by dividing the nozzle columns  146  into the color image forming nozzle groups and the toned-white image forming nozzle groups only in the case of printing both of the color image and the toned-white image.