Patent Publication Number: US-2011075172-A1

Title: Print information acquiring method, print information acquiring apparatus, profile generating method, and computer-readable recording medium with program recorded therein

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Applications No. 2009-228984 filed on Sep. 30, 2009, No. 2010-041078 filed on Feb. 25, 2010 and No. 2010-041080 filed on Feb. 25, 2010, of which the contents are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a print information acquiring method, a print information acquiring apparatus, a profile generating method, and a computer-readable recording medium with a program recorded therein for measuring color values of management patches added to a print and acquiring print information of the print based on the measured color values. 
     2. Description of the Related Art 
     With significant advances in inkjet technology in recent years, it is becoming possible for inkjet printers to produce large color prints of high quality at high speeds. Inkjet printers are not only popular for private or home use, but also are widely used in commercial applications nowadays. Inkjet printers make it possible to print on POP (Point Of Purchase) posters, wall posters, large-size mediums such as outdoor advertisements and billboards, roll mediums, and thick hard mediums. 
     There are a wide variety of print mediums (hereinafter also referred to as “mediums”) available for use in prints to meet various commercial demands. For example, such print mediums include paper mediums such as synthetic paper, thick paper, aluminum-evaporated paper, etc., resin mediums such as vinyl chloride, PET, etc., and tarpaulin paper made of woven fiber cloth with synthetic resin films applied to both surfaces thereof. 
     Since advertisement prints are expected to be effective to arouse consumer&#39;s motivation to buy advertised products through the consumer&#39;s visual sensation, the color finish of prints is of particular importance. Heretofore, there have been disclosed various color matching technologies such as a method of generating an ICC (International Color Consortium) profile, a method of adjusting a designated color, etc., as print color managing means. According to such disclosed color matching technologies, it is the general practice to print a color chart including a plurality of color patches of different colors with a printing machine, and to feed back evaluation results of the color chart to the printing machine. 
     For example, a color chart printed by a printing machine and having color patches of 100 through 1000 colors is measured by a colorimeter, and an ICC profile of the printing machine can be generated based on the measured color values. Furthermore, an operator can visually recognize a color chart, the colors of which are gradually changed in the vicinity of a designated color, can select the color of a color patch judged as being closest to the designated color, and can make fine adjustments to match the selected color. 
     For accurately reproducing colors on the printing machine and making fine color adjustments, it is desirable for print information of a color chart, which has actually been measured or evaluated, to be capable of being tracked down. The print information refers to various items of information about printing, and signifies a broad concept covering not only printing conditions including a printing mode, a print medium type, etc., but also an intended application, a printing machine identification number, a designated color number, etc. 
     There has been proposed, as one process of checking preset print information against a printed color chart and managing the print information without fail, a process of embedding each item of print information based on the colors of color patches and their layout. The proposed process allows a colorimeter to be used in place of a readout means for reading an identification code such as a bar code or the like, and further makes it possible to identify print information correctly with a few color patches. 
     Japanese Laid-Open Patent Publication No. 2005-328255 discloses a color chart wherein a certain color is selected from color proof color patches and the position of the color patch of the certain color is changed depending on preset printing conditions. The publication also discloses a system for and a method of identifying printing conditions for the color chart by measuring the color chart with a colorimeter and acquiring positional information (an address) of the color patch of the certain color on the color chart. 
     Japanese Laid-Open Patent Publication No. 2007-221571 discloses a color chart having management patches (corresponding to “attribute specifying color patches” in Claim 1 of Japanese Laid-Open Patent Publication No. 2007-221571) in addition to color proof patches. This publication also discloses a system and method of identifying printing conditions for the color chart by measuring the color chart with a colorimeter, selecting one of the color proof patches that has the same color as the management color patch, and acquiring positional information (an address) of the selected color proof color patch on the color chart. 
     The methods revealed in Japanese Laid-Open Patent Publication No. 2005-328255 and Japanese Laid-Open Patent Publication No. 2007-221571 share a technical concept by which two-dimensional positional information on a color chart is referred to and converted into print information. 
     However, since the positional information on the color chart is directly related to elements of the print information, even when a color chart is printed by the same printing machine, management patches on the color chart cannot be used as a means for acquiring print information. 
     For example, the process disclosed in Japanese Laid-Open Patent Publication No. 2005-328255 cannot be applied to a color chart including only designated colors or colors in the neighborhood of such designated colors (hereinafter referred to as a “designated color adjusting color chart”), because color intervals of the color patches are so small that it is difficult to detect colors appropriately, and thus, erroneous identification of print information may occur. 
     According to the process disclosed in Japanese Laid-Open Patent Publication No. 2007-221571, the definition of positions (addresses) of the color patches has to be changed each time details plotted (recorded) on the color chart, particularly the number and array of color patches, are changed. 
     Details plotted on prints other than color charts do not include color patches that refer to positional information within print areas thereof. Therefore, management patches cannot be used on these types of prints either. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a print information acquiring method, a print information acquiring apparatus, a profile generating method, and a computer-readable recording medium with a program recorded therein, for acquiring print information of prints without losing consistency in a printing machine when different types of color charts and prints other than color charts are printed by the printing machine. 
     According to the present invention, there is provided a print information acquiring method comprising the steps of generating an association table associating print information with color values, encoding print information of a print into prescribed color values based on the generated association table, adding image data of management patches having the prescribed color values to image data for printing the print, acquiring color values of the management patches added to the print that is printed by a printing machine, and decoding the acquired color values of the management patches into the print information based on the association table, wherein in the step of generating the association table, the association table is generated depending on a gamut of the printing machine. 
     According to the present invention, there also is provided a print information acquiring apparatus comprising an association table generator for generating an association table associating print information with color values, an encoding processor for encoding print information of a print into prescribed color values based on the association table generated by the association table generator, a patch adder for adding image data of management patches having the prescribed color values to image data for printing the print, a colorimetric unit for acquiring color values of the management patches added by the patch adder to the print that is printed by a printing machine, and a decoding processor for decoding the color values of the management patches acquired by the colorimetric unit into the print information based on the association table, wherein the association table is generated depending on a gamut of the printing machine. 
     According to the present invention, there is provided a profile generating method comprising the steps of generating an association table associating print information with color values, encoding print information of a color chart having a plurality of color patches into prescribed color values based on the generated association table, adding image data of management patches having the prescribed color values to image data for printing the color chart, acquiring color values of the color patches and color values of the management patches added to the color chart that is printed by a printing machine, decoding the acquired color values of the management patches into the print information based on the association table, and generating a profile based on the acquired color values of the color patches and the decoded print information. 
     According to the present invention, there is provided a computer-readable recording medium storing therein a program for enabling a computer to perform the functions of generating an association table associating print information with color values, depending on a gamut of a printing machine for printing a print, encoding print information of the print into prescribed color values based on the generated association table, adding image data of management patches having the prescribed color values to image data for printing the print, acquiring color values of the management patches added to the print that is printed by the printing machine, and decoding the color values of the acquired management patches into the print information based on the association table. 
     With the print information acquiring method, the print information acquiring apparatus, the profile generating method, and the computer-readable recording medium with a program recorded therein according to the present invention, an association table is generated that associates print information with color values, print information of a print is encoded into prescribed color values based on the generated association table, image data of management patches having the prescribed color values are added to image data for printing the print, color values of the management patches added to the print that is printed by a printing machine are acquired, and the acquired color values of the management patches are decoded into the print information based on the association table, wherein the association table is generated depending on a gamut of the printing machine. The print information thus can be acquired independently of plotted (recorded) contents of the print. Color values in a range where colors can be reproduced by the printing machine and the print information can appropriately be associated with each other. Even when different types of color charts and prints other than color charts are printed, print information of the prints can be acquired without loss of consistency within the same printing machine. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a printing system according to an embodiment of the present invention; 
         FIG. 2  is a front elevational view of a profile color chart according to the embodiment; 
         FIG. 3  is a front elevational view of a designated color adjusting color chart according to the embodiment; 
         FIG. 4  is a functional block diagram of an image processing apparatus according to the embodiment; 
         FIG. 5  is a flowchart of a sequence for producing a print having appropriate colors with the printing system according to the embodiment; 
         FIG. 6  is a flowchart of a sequence for adding management patches with encoded print information to a print; 
         FIG. 7  is a diagram showing by way of example a color association table generated by an association table generator according to the embodiment; 
         FIG. 8  is a flowchart of a sequence for acquiring print information from management patches added to a print; 
         FIG. 9  is a graph illustrating time-dependent changes in color differences on a print, which are caused by dry-down; 
         FIG. 10A  is a functional block diagram showing processing details of a time manager upon notification of a color chart printing request; 
         FIG. 10B  is a functional block diagram showing processing details of the time manager upon notification of completion of colorimetric measurement; 
         FIG. 11  is a graph showing a positional relationship between the gamuts of two printing machines; 
         FIG. 12  is a diagram illustrating a process of setting ID numbers for three printing machines; 
         FIGS. 13A and 13B  are conceptual diagrams showing examples of determining ink amounts used to print management patches; and 
         FIG. 14  is a front elevational view of a profile color chart according to a modification of the embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A print information acquiring method according to a preferred embodiment of the present invention, in relation to a print information acquiring apparatus and a printing system for carrying out the print information acquiring method, will be described in detail below with reference to the accompanying drawings. 
       FIG. 1  shows in perspective a printing system  10  incorporating an image processing apparatus  16  as a print information acquiring apparatus according to an embodiment of the present invention. 
     As shown in  FIG. 1 , the printing system  10  basically comprises a LAN  12 , an editing apparatus  14 , an image processing apparatus  16 , a printing machine  18 , and a colorimeter (colorimetric unit)  20 . 
     The LAN  12  is a network constructed according to communication standards such as Ethernet (registered trademark) or the like. The editing apparatus  14  and the image processing apparatus  16  are connected to each other as well as to a database DB by a wired or wireless link through the LAN  12 . 
     The editing apparatus  14  is capable of editing an arrangement of color images made up of characters, figures, pictures, photos, etc., on each of pages to be printed. The editing apparatus  14  generates electronic manuscripts in a page description language (hereinafter referred to as “PDL”), e.g., 8-bit image data in color channels made up of four colors (C, M, Y, K) or three colors (R, G, B). 
     PDL refers to a language that is descriptive of image information, including format information, positional information, color information (including density information), etc., of characters, figures, etc., in a “page” that serves as an output unit for printing, displaying, or the like. Known types of PDL include PDF (Portable Document Format according to ISO32000-1:2008), PostScript (registered trademark) of AdobeSystems, and XPS (XML Paper Specification). 
     A color scanner, not shown, is connected to the editing apparatus  14 . The color scanner is capable of optically reading a color original set in position. Therefore, the editing apparatus  14  can acquire color image data from the color scanner, based on the color original read thereby, as image data of an electronic manuscript. 
     The image processing apparatus  16  converts color image data of an electronic manuscript described by PDL and acquired from the editing apparatus  14  into bitmap image data (a type of raster image data), performs desired image processing, e.g., a color conversion process, an image scaling process, an image arranging process, etc., on the bitmap image data, converts the processed bitmap image data into print signals that match the printing process of the printing machine  18 , and sends the print signals to the printing machine  18 . 
     The image processing apparatus  16  comprises a main unit  22  including a CPU, a memory, etc., a display device  24  for displaying color images, and an input device  26  serving as an input unit including a keyboard  28  and a mouse  30 . The colorimeter  20  is connected to the main unit  22  of the image processing apparatus  16 . 
     The printing machine  18  comprises an inkjet printing apparatus for producing a color image based on a combination of standard inks of colors C, M, Y, K (process colors) and optional inks of light colors such as LC, LM, etc., and W (white). The printing machine  18  controls propulsion of inks onto a print medium  32  (rolled non-printed medium in  FIG. 1 ) based on print signals received from an external apparatus, e.g., the image processing apparatus  16 , in order to print a color image on the print medium  32 , thereby producing a print  34 , which may include a profile color chart  34   p  and a designated color adjusting color chart  34   c.    
     The print medium  32  may comprise a paper medium such as synthetic paper, thick paper, aluminum-evaporated paper, or the like, a resin medium such as vinyl chloride, PET, or the like, or tarpaulin paper, or the like. 
     The colorimeter  20  measures color values of an object to be measured. Such color values refer not only to tristimulus values X, Y, Z, the coordinates L*, a*, b of a uniform color space, etc., but also to a distribution of optical physical values (hereinafter referred to as “spectral data”) with respect to wavelengths, e.g., a spectral radiance distribution, a spectral sensitivity distribution, a spectral reflectivity, or a spectral transmittance. 
       FIG. 2  is a front elevational view of a profile color chart  34   p  according to the first embodiment. 
     The profile color chart  34   p  shown in  FIG. 2  comprises 100 color patches  36  of different colors, which are substantially identical in shape and arranged in rows and columns, a sequence of numbers  38  and a sequence of alphabetical letters  40  for identifying positions of the color patches  36  along directions of the rows and columns, and management patches  42  for identifying printing conditions for printing the profile color chart  34   p,  all of which are printed on the print medium  32 . 
     The color patches  36  are arranged in a matrix having 10 vertical columns and 10 horizontal rows. The color patches  36  in each of the vertical columns are held together closely with no spaces therebetween, whereas the color patches  36  in each of the horizontal rows are spaced by given intervals. Colors of the respective color patches  36  are set to given values within a range of signal levels made up of C, M, Y, K values (a percentage range from 0% to 100%, or an 8-bit gradation range from 0 to 255). 
     The sequence of numbers  38  represents a vertical string of characters ranging from (01) to (10) positioned to the left of the respective rows of color patches  36  in alignment with the rows. The sequence of alphabetical letters  40  represents a horizontal string of characters ranging from (A) to (J) positioned at the top of the respective columns of color patches  36  in alignment with the columns. 
     The management patches  42  include, successively from the left, one head patch  42   a,  four print information patches  42   b,  one checksum patch (colorimetry success/failure detecting patch)  42   c,  and one tail patch  42   d.    
       FIG. 3  is a front elevational view of a designated color adjusting color chart  34   c  according to the present embodiment. 
     The designated color adjusting color chart  34   c  shown in  FIG. 3  comprises 49 color patches  44  of different colors that are substantially identical in shape, row numbers  46  and column numbers  48  for identifying positions of the color patches  4  along directions of the rows and columns, and management patches  42  for identifying printing conditions for printing the designated color adjusting color chart  34   c,  all of which are printed on the print medium  32 . 
     The color patches  44  are arranged in a matrix having 7 vertical columns and 7 horizontal rows, which are spaced from each other by given intervals. Colors of the respective color patches  44  are set to given values in a range of signal levels made up of C, M, Y, K values (a percentage range from 0% to 100%, or an 8-bit gradation range from 0 to 255). 
     The row numbers  46 , which serve as identification information, represent a vertical string of characters ranging from (+3) to (−3) positioned to the left of the respective rows of color patches  44  in alignment therewith. The column numbers  48 , which also serve as identification information, represent a horizontal string of characters ranging from (−3) to (+3) positioned at the top of the respective columns of color patches  44  in alignment therewith. 
     The management patches  42  are identical to the management patches  42  shown in  FIG. 2  and will not be described in detail. 
       FIG. 4  shows in block form the image processing apparatus  16  according to the present embodiment. In  FIG. 4 , an electronic manuscript is supplied along directions indicated by the outlined solid-line arrows. Color-chart image data is supplied along directions indicated by the outlined broken-line arrows. Various other data are supplied along directions indicated by the solid-line arrows. 
     As shown in  FIG. 4 , the main unit  22  of the image processing apparatus  16  includes an I/F  60  for entering an electronic manuscript supplied from the editing apparatus  14 , an RIP (Raster Imaging Processor)  62  for converting the PDL format of the electronic manuscript supplied from the I/F  60  into a raster format, a color converter  64  for performing a color converting process on the converted C, M, Y, K values (or R, G, B values) of the electronic manuscript from the RIP  62  in order to produce image data having new C, M, Y, K values, a printing machine driver  66  for converting the image data, which is made up of new C, M, Y, K values produced by the color converter  64 , into print control signals (ink propulsion control data) that match the printing machine  18 , and an I/F  68  for outputting the print control signals generated by the printing machine driver  66  to the printing machine  18 . 
     The main unit  22  also includes a color manager  70  for managing profiles of different printing machines  18 , an image data generator  72  for generating image data to print the designated color adjusting color chart  34   c  or the profile color chart  34   p,  a time manager  74  for managing various times such as a printing request time, a colorimetry completion time, etc., an I/F  76  for connection to the display device  24 , an I/F  78  for connection to the input device  26  including the keyboard  28  and the mouse  30 , and an I/F  80  for connection to the colorimeter  20 . 
     The main unit  22  also includes a storage unit  82  for storing various data supplied from various components of the main unit  22 , and for supplying stored data to various components of the main unit  22 . The storage unit  82  is connected respectively to the RIP  62 , the color converter  64 , the color manager  70 , the image data generator  72 , the time manager  74 , the I/F  76 , the I/F  78 , and the I/F  80 . 
     The color converter  64  comprises a target profile processor  84  for converting device-dependent data into device-independent data, and a print profile processor  86  for converting device-independent data into device-dependent data. Device-dependent data refer to data defined in terms of C, M, Y, K values, R, G, B values, or the like, for appropriately driving various devices. Device-independent data refer to data defined in terms of a display system such as an HSL system, an HSB system, a CIELAB coordinate system, a CIELUV coordinate system, an XYZ system, or the like. 
     The image data generator  72  comprises a designated color adjusting data generator  88  for generating image data to print the designated color adjusting color chart  34   c,  a profile data generator  90  for generating image data to print the profile color chart  34   p,  and a management patch adder (patch adder)  92  for adding management patches  42  to a given position in addition to the image data. 
     The color manager  70  comprises an association table acquirer  93  for acquiring a color association table (association table), to be described later, from an external device through the I/F  60 , a profile generator  94  for generating profiles for respective printing machines  18 , a color ID manager  96  for managing color IDs for the management patches  42 , and a data converter  98  for converting various data, such as data of printing conditions, according to prescribed rules. The data converter  98  comprises an association table generator  100  for generating a color association table, which associates color values, e.g., L*, a*, values, with print information, an encoding processor (printing time acquirer)  102  for encoding print information into color values, a decoding processor  104  for decoding color values into print information, a detector  106  for detecting a head patch  42   a  or a tail patch  42   d  of the management patches  42 , a decision unit  108  for determining whether or not the colorimeter  20  has successfully acquired color values, and a predictor  109  for predicting color values of the management patches  42  in a steady state of dry-down. 
     The RIP  62  can perform various image processing functions, including an image scaling process depending on the resolution, etc., of the printing machine  18 , and a rotating and inverting process depending on a printing format used when an electronic manuscript is converted into raster image data. 
     From the C, M, Y, K values, the printing machine driver  66  generates ink propulsion control data corresponding to ink colors (C, M, Y, K, LC, LM, or W). Such ink propulsion control data control the printing machine  18  so as to eject inks appropriately (ink ejection ON/OFF, ink dot diameters, etc.). The printing machine driver  66  may generate ink propulsion control data according to a known algorithm, such as a dither matrix method, an error diffusion method, or the like, although conversion thereof is required from an 8-bit multiple-gradation image into a low-gradation image such as a binary image. 
     The target profile processor  84  or the print profile processor  86  is capable of correcting a profile depending on a print mode of the printing machine  18 . The print mode refers to various print settings, such as the number of nozzles of the print head, the timing (unidirectional/bidirectional) of ink ejection as the print head scans, the number of passes, the number and types of inks used in the printing machine  18 , an algorithm for generating ink propulsion control data, etc. 
     The main unit  22  has a controller (not shown) comprising a CPU, etc., for controlling all of the image processing functions described above. Specifically, the controller controls not only operations of various components of the main unit  22 , e.g., reading data from and writing data to the storage unit  82 , but also transmission of display signals via the I/F  76  to the display device  24 , and acquisition of colorimetric data from the colorimeter  20  via the I/F  80 . 
     The image processing apparatus  16  according to the present embodiment is constructed as described above. The image processing functions described above can be performed according to application programs stored in the storage unit  82 , which operate under the control of a basic program (operating system). 
     Such programs may be recorded in a computer-readable recording medium, and may be read into a computer system and executed thereby. The term “computer system” includes an operating system (OS) and hardware including peripheral devices. The computer-readable recording medium comprises a portable medium such as a flexible disk, a magnetooptical disk, a CD-ROM, or the like, or a storage unit such as a hard disk or the like incorporated in the computer system. The computer-readable recording medium may also include a medium for dynamically holding programs for a short period of time, such as a communications line for transmitting programs via a network such as the Internet or the like, a communication channel such as a telephone line, or a memory for holding programs for a certain period of time such as a volatile memory in a computer system, which operates as a server or client in a network environment. 
     The printing system  10  according to the present embodiment is basically constructed as described above. Operations of the printing system  10  will be described below. 
       FIG. 5  is a flowchart of a sequence for producing a print  34  having appropriate colors using the printing system  10 . A process of producing a print  34  will be described below, mainly with reference to  FIGS. 1 and 5 . 
     The operator examines printing conditions and observational manners of a print  34  to be produced (step S 1 ). Printing conditions refer to the type of printing machine  18  used to produce the print  34 , the type of the print medium  32 , or a printing mode as referred to above. Observational manners refer not only to attributes (type and spectral data) of an observational light source for the print  34 , but also refer to the image type of the print  34  to be observed. The image type may represent a reflective image, i.e., an image observed with a reflective light source used as a main light source, a transmissive image, i.e., an image observed with a transmissive light source used as a main light source, or a combined image, i.e., an image observed with a reflective light source and a transmissive light source used together as main light sources. 
     Then, the operator selects a profile suitable for the printing machine  18  (step S 2 ). Normally, a target profile or a print profile is stored in the storage unit  82 . If a profile suitable for the printing machine  18  is not registered, i.e., is not stored in the storage unit  82 , then a print profile can be generated separately. 
     Then, an electronic manuscript is printed using the printing machine  18 , thereby producing a color print  34  (step S 3 ). The print  34  may be laminated by a laminating apparatus, not shown, in order to provide a protective film over the image surface of the print  34 . The color image of the print  34  can thus be protected to provide better abrasion resistance and toughness. 
     Then, the operator evaluates the color of the color image of the print  34  (step S 4 ), and determines whether or not the color of the image is appropriate (step S 5 ). The operator may evaluate the color of the image in order to determine whether desired hues are obtained either by visually checking the image based on observation of an overall or partial appearance of the image, or by obtaining color values of a certain area of the print  34  with the colorimeter  20 , and determining whether the obtained color values fall within a desired range. 
     If, as a result of such image evaluation, the operator judges that the image of the print  34  is not suitable, then the operator changes the profile so as to make fine adjustments to the color of the image (step S 6 ). Specifically, the operator may reset the profile or regenerate a new profile, or make fine adjustments to the profile, i.e., the operator may correct the presently set profile, or may correct the print data of the electronic manuscript. 
     Thereafter, an electronic manuscript is printed and the color of the printed image is evaluated repeatedly (steps S 3  through S 6 ) until a print  34  having a desired color is obtained. 
     An image processing sequence of the image processing apparatus  16  for printing an electronic manuscript (step S 3 ) will be described in detail below with reference to  FIG. 4 . 
     When an electronic manuscript in PDL format supplied from the editing apparatus  14  is input to the image processing apparatus  16  via the LAN  12  and the I/F  60 , the electronic manuscript is converted into 8-bit C, M, Y, K raster data (device-dependent image data) by the RIP  62 . The 8-bit C, M, Y, K raster data then are converted into L*, a*, b* data (device-independent image data) by the target profile processor  84 . The L*, a*, b* data then are converted into C, M, Y, K value data (device-dependent image data) by the print profile processor  86 . The C, M, Y, K value data then are converted into print control signals (ink propulsion control data) by the printing machine driver  66 . The print control signals are supplied from the printing machine driver  66  via the I/F  68  to the printing machine  18 . If necessary, C, M, Y, K raster data produced by the RIP  62  are temporarily stored in the storage unit  82 . Thereafter, the printing machine  18  produces a desired print  34  based on the print control signals. 
     Since target profiles and print profiles corresponding to a plurality of set conditions have been stored in the storage unit  82 , a target profile is supplied selectively to the target profile processor  84 , and a print profile is supplied selectively to the print profile processor  86 , depending on various preset conditions. If profiles are corrected appropriately in view of the print mode of the printing machine  18 , then more appropriate color conversion processes can be performed. 
     An image processing sequence of the image processing apparatus  16  for generating a profile (step S 2 ) will be described in detail below with reference to  FIG. 4 . 
     Image data generated by the profile data generator  90  based on given C, M, Y, K value data stored in the storage unit  82  are supplied from the image data generator  72  via a path represented by the outlined broken-line arrow to the printing machine driver  66 . The image data are supplied from the printing machine driver  66  to the printing machine  18 , in the same manner as when an electronic manuscript is printed. The color patches  36  (see  FIG. 2 ) of the profile color chart  34   p  thus produced are measured by the colorimeter  20 , thereby producing color values L*, a*, b*. The color value data thus produced are temporarily stored in the storage unit  82 . Thereafter, based on an associative relationship between the designated C, M, Y, K value data and the produced color values L*, a*, b*, a print profile is generated, which includes data representing a three-dimensional to four-dimensional conversion LUT. 
     The process of producing a print  34  of appropriate colors using the printing system  10 , i.e., a direct color managing process, has been described above. An indirect color managing process based on management of print information, or more specifically, a process of adding print information of the printing machine  18  to the print  34  (or acquiring print information of the printing machine  18  from the print  34 ) using the management patches  42 , will be described in detail below. 
       FIG. 6  is a flowchart of a sequence for adding management patches  42  with encoded print information therein to the print  34 . According to this sequence, management patches  42  are added to the profile color chart  34   p  shown in  FIG. 2 , for example. 
     A print profile suitable for the printing machine  18  is selected (step S 101 ). Specifically, print profiles are stored in advance in the storage unit  82  shown in  FIG. 4 . One of the print profiles stored in the storage unit  82 , which is identical to a profile supplied to the print profile processor  86 , is selected automatically or manually. 
     Then, gamut information of the printing machine  18  is acquired (step S 102 ). More specifically, the gamut information of the printing machine  18  is acquired based on the print profile selected in step S 101 . Gamut information refers to information representing the configuration of a gamut region in a uniform color space, e.g., an L*a*b* space. The configuration of the gamut region represents the volume, shape, positional relationship, etc., of the gamut region. 
     Then, a color association table is generated based on the acquired gamut information of the printing machine  18  (step S 103 ). More specifically, a color association table is generated by the association table generator  100 , and then, if necessary, the color association table is stored in the storage unit  82  (see  FIG. 4 ). Alternatively, color association tables may be stored in the database DB (see  FIG. 1 ), and a desired one of the stored color association tables may be acquired from the database DB. In this case, depending on a request from the main unit  22 , a color association table suitable for the printing machine  18  and/or the print medium  32  is selected from the database DB. The selected color association table is supplied through the LAN  12  and the I/F  60 , and is acquired by the association table acquirer  93 . 
       FIG. 7  is a diagram illustrating, by way of example, a process of determining addresses of a color association table.  FIG. 7  shows an a*b* plane in an L*a*b* space. 
     A defined gamut  110  of the printing machine  18  includes a proximity area  111  near the boundary of the gamut  110 , and an encoding area  112  inside of the proximity area  111 . As described later, the proximity area  111  tends to have unstable color reproducibility, whereas the encoding area  112  tends to have higher color reproducibility. The readout success rate for the management patches  42  is made higher by using colors in the encoding area  112 , rather than using colors in the proximity area  111 . 
     The association table generator  100  sets target color values  114  from among innumerable colors in the encoding area  112  according to prescribed rules. For setting such target color values  114 , a variety of setting methods are available, and various types of algorithms can be used. For example, in order for the association table generator  100  to be able to generate color association tables from various gamut configurations according to the same rules, the target color values  114  may be arranged in a grid-like pattern such that color differences between adjacent target color values  114  are substantially equal to each other. 
     Thereafter, the association table generator  100  assigns different associated numbers to the respective target color values  114 , thereby generating a suitable color association table. In  FIG. 7 , the assigned associated numbers are arranged in a spiral pattern that starts at the origin (L* axis). Values of the associated numbers, and the order of assignment of the associated numbers are not limited to those shown in  FIG. 7 . 
     In conjunction with generation of the color association table, an allowable range for errors in color differences between the target color values  114  is established. Such errors in color differences refer to deviations of color reproduction due to performance variations of the colorimeter  20  or the printing machine  18  and due to dry-down. As shown in  FIG. 7 , closed spaces (color areas)  116  around the respective target color values  114  are established as an allowable range. 
     Then, a maximum amount of information per print information patch  42   b  is determined (step S 104 ). Unless color limitations are imposed on the print information patches  42   b,  the maximum amount of information is equal to the total number of closed spaces  116  to which the associated numbers have been assigned in step S 103 . The total number of closed spaces  116  is represented by N. 
     Then, a number of print information patches  42   b  to be added to the profile color chart  34   p  is determined (step S 105 ). More specifically, the color ID manager  96  (see  FIG. 4 ) determines the number of print information patches  42   b  in excess of the total amount of data that makes up the print information. The number of print information patches  42   b  may be a fixed value, or may be changed depending on the total amount of data that makes up the print information. In this case, the number of print information patches  42   b  is represented by M. 
     Thereafter, the print information is encoded (step S 106 ). Print information of the printing machine  18  is encoded by the encoding processor  102  (see  FIG. 4 ) based on the color association table generated in step S 3 , and then the print information is converted into L*, a*, b* values. Certain specific encoding processes will be described below. 
     According to the first encoding process, a given ID number is assigned to the associated print information. In other words, combinations of variables (the print mode, the type of the print medium  32 , the intended application, the identification number of the printing machine  18 , the color sample number of the designated color, etc.) of the print information are uniformly managed by ID numbers. 
     According to the second encoding process, variables of the print information are correlated in advance with associated numbers of the color association table. For example, the state of a certain ON print mode is correlated with “1”, and the state of an OFF print mode is correlated with “0”. The print information is encoded by a combination of associated numbers, which are correlated with the variables. 
     According to the third encoding process, variables of the print information are converted into codes, and values of the codes are correlated with associated numbers of the color association table. For example, a registered name “PRINTER-1” of the printing machine  18  is converted into an ASCII code, and the value of the ASCII code is correlated with an associated number of the color association table. 
     Using any one of the aforementioned encoding processes, it is possible to embed a large amount of print information in one print information patch  42   b.    
     A specific example of the first encoding process will be described below. It is assumed that a given ID number x is a 6-figure numerical value in decimal notation, which is encoded by two colors (L* 1 , a* 1 , b* 1 ) and (L* 2 , a* 2 , b* 2 ). For example, the color values can be calculated according to the following equations (1) through (6): 
         L*   1   =k ×Int{ x /(10̂5)}+ h    (1)
 
         a*   1   =k ×Int{ x /(10̂4)}+ h    (2)
 
         b*   1   =k ×Int{ x /(10̂3)}+ h    (3)
 
         L*   2   =k ×Int{ x /(10̂2)}+ h    (4)
 
         a*   2   =k ×Int{ x /(10̂1)}+ h    (5)
 
         b*   2   =k ×Int{ x /(10̂0)}+ h    (6)
 
     Within the range of the given ID numbers, k and h can be determined in advance such that either one of the calculated two colors (L* 1 , a* 1 , b* 1 ) and (L* 2 , a* 2 , b* 2 ) will fall within the range of the gamut. Assuming the ID numbers can be encoded and decoded, then notation of the ID number x is not limited to decimal notation, but may be selected as desired. 
     Then, a checksum of the management patches  42  is calculated (step S 107 ). For example, the value of the checksum may be set to a remainder value. Specifically, the value of the checksum may be set to {N−mod(ΣV i , N)}mod(N), where mod represents a modulus operator and {V i } (i=1, . . . , M) represents a value of each print information patch. In this manner, the color of the checksum patch  42   c  is determined. 
     The encoding processor  102  also determines colors of the head patch  42   a  and the tail patch  42   d  of the management patches  42 . For example, colors that are not used as colors of the color patches  36  or of other management patches  42  may be selected as colors of the head patch  42   a  and the tail patch  42   d,  so as to make them easily detectable. 
     Finally, image data for forming the management patches  42  are generated and added to a portion of the other image data region (step S 108 ). More specifically, the management patch adder  92  replaces a portion of the image data generated by the profile data generator  90  with the image data for forming the management patches  42 . The management patches  42  may be placed in a location the can easily be distinguished from the color patches, or at a location that can easily be measured colorimetrically by the operator. 
     The profile color chart  34   p,  including the management patches  42  added thereto as print information, is finally printed by the printing machine  18  (step S 109 ). Similarly, the management patches  42  also are added to the designated color adjusting color chart  34   c.    
     A specific process of acquiring print information from the management patches  42  added to the print  34  will be described below with reference to the flowchart shown in  FIG. 8 . According to this process, management patches  42  are added to the profile color chart  34   p  shown in  FIG. 2 , for example. 
     First, the management patches  42  are colorimetrically measured (step S 201 ). Specifically, the operator measures colorimetrical values of the management patches  42  successively from the head patch  42   a  to the tail patch  42   d,  or from the tail patch  42   d  to the head patch  42   a.  Either the head patch  42   a  or the tail patch  42   d  may be used as a measurement start position, while the other is used as a measurement end position. The color patches  36  on the profile color chart  34   p  may be colorimetrically measured in any order. 
     Then, the head patch  42   a  is detected (step S 202 ). Specifically, color values of the head patch  42   a  are detected by the detector  106  from at least one of the acquired color values. If color values, which are not used for any of the color patches  36  or the other management patches  42 , are selected as color values for the head patch  42   a,  then the head patch  42   a  can more easily be detected. 
     Then, color values of the other management patches  42  are detected (step S 203 ). In  FIG. 2 , the operator detects color values of the four print information patches  42   b,  the checksum patch  42   c,  and the tail patch  42   d,  in that order. Then, it is determined whether or not the color values L*, a*, b* fall within a prescribed range (step S 204 ). If the color values L*, a*, b* fall within the prescribed range, then the color values are decoded (step S 206 ). If color values are represented by P 1  as shown in  FIG. 7 , then since the color values fall within the closed space  116  of the target color value  114 , to which the associated number “07” is assigned, such color values are decoded into “07”. Since the color values are decoded based on whether they fall within the closed spaces  116  or not, the color values can be decoded while taking into account printing and colorimetric variations. 
     The color association table is prepared such that the closed spaces  116  do not overlap with each other, and so that the color values can be decoded uniquely even in the presence of printing and colorimetric variations. The closed spaces  116  may be established such that the maximum color difference between two points in one closed space  116  lies within a range of from 5 to 15. 
     If the encoding area  112  is defined by color values L*, a*, b* where 20≦L*≦80, −30≦a*≦30, and −30≦b*≦30, then the encoding area  112  has a volume of 60×60×60=216000. If one code is assigned to a cube having sides each represented by 6, then the encoding area  112  can produce a maximum of 1000 codes. 
     The color association table may be generated depending on density variation characteristics (see  FIG. 9 ) of the print  34  due to dry-down. For example, if the density variations are large, then the intervals between the target color values  114  can be increased, and also, the size of the closed spaces  116  can be increased. In this manner, color values can appropriately be decoded with time-dependent changes in density due to dry-down being taken into account. In other words, the operator does not need to wait until the printed density becomes stabilized after the print  34  has been printed. 
     The color association table may be generated without using color values in the proximity area  111  near the boundary of the gamut  110  of the printing machine  18 . By excluding the proximity area  111  where color reproduction accuracy is lower, and by using color values within the encoding area  112  where color reproduction accuracy is higher, the accuracy (success rate) with which the color values are decoded into print information is further increased. 
     Moreover, the closed spaces  116  may be reduced in size within a range of color values where color reproducibility of the printing machine  18  is higher, and increased in size within a range of color values where color reproducibility of the printing machine  18  is lower, so that color values can appropriately be decoded while taking into consideration such higher and lower color reproducibility. 
     The closed spaces  116  are not limited to spherical shapes (see  FIG. 7 ), but may be of a cubic shape, a regular trioctahedral shape, or the like. The closed spaces  116  may be identical in shape to each other in order to simplify the calculating process for determining whether or not the color values exist within the closed spaces  116 . 
     The algorithm for generating the color association table may be changed depending on the gamut, so as to efficiently utilize the encoding area  112  and to assign more numbers thereto. 
     If the color values L*, a*, b* do not fall within a prescribed range (step S 204 ), then the color manager  70  outputs a warning indicating the acquisition of wrong color values (step S 205 ). The warning may be displayed on the display device  24 . The decoding processor  104  selects a target color value  114 , which is closest to the acquired color values, and decodes the color values according to the selected target color value  114 . More specifically, if as shown in  FIG. 7  the color values are represented by P 2 , then the color values do not fall within any of the closed spaces  116 , and the color values are decoded into “06” assigned to a target color value  114  that is closest to P 2 . 
     Next, it is determined whether or not the tail patch  42   d  has been detected (step S 207 ). If the tail patch  42   d  is not detected, the processes of steps S 203  through S 207  are repeated. Specifically, the color values of the tail patch  42   d  are detected from at least one of the acquired color values detected by the detector  106 . If color values, which are not used for any of the color patches  36  or the other management patches  42 , are selected as color values for the tail patch  42   d,  then the tail patch  42   d  can easily be detected. 
     If the tail patch  42   d  is detected, then the decoded values are combined to restore the print information of the printing machine  18  (step S 208 ). 
     Then, a checksum is confirmed (step S 209 ). More specifically, the decision unit  108  (see  FIG. 4 ) divides the sum of the values of the four print information patches  42   b  and the checksum patch  42   c  by N to calculate a remainder value. If the remainder value is 0, then the decision unit  108  judges that all the color values have properly been measured (OK). If the remainder value is not 0, then the decision unit  108  judges that at least one of the color values is improper (NG). 
     If the decision unit  108  judges OK, then the read print information is displayed (step S 210 ). For example, print information of the profile color chart  34   p  is displayed on the display device  24  in order for the operator to confirm the print information with ease. 
     If the decision unit  108  judges NG, then a reading error is displayed (step S 211 ). At this time, depending on the confirmed checksum (remainder value), the source or cause of the error, e.g., the colorimeter  20 , the printing machine  18 , or dry-down, may be determined and displayed on the display device  24 . 
     Then, a time for printing the profile color chart  34   p  is acquired (step S 212 ). If the read print information includes a time for printing the profile color chart  34   p,  then the time included therein may be acquired. 
     Next, the decision unit  108  determines whether or not a given period (first threshold value) has elapsed from printing of the profile color chart  34   p  (step S 213 ). The first threshold value represents a period that is long enough for any significant time-dependent variations of the color patches  36  due to dry-down to die out. Further details of the first threshold value will be described later. 
     If the period that has elapsed from the time that the profile color chart  34   p  was printed exceeds the first threshold value, then the operator measures the color patches  36  of the profile color chart  34   p  with the colorimeter  20  (step S 214 ). The process of generating a print profile using the acquired color values has already been described above, and will not be described below. 
     If the period that has elapsed from the time that the profile color chart  34   p  was printed does not exceed the first threshold value, then the decision unit  108  issues a warning indicating that the decision unit is still waiting for a certain period of time (step S 215 ). In addition to the warning, the decision unit  108  may also display a remaining time until the certain period of time elapses. 
     In this manner, print information is acquired from the management patches  42 , which are added to the profile color chart  34   p.  Similarly, print information is acquired from the management patches  42 , which are added to the designated color adjusting color chart  34   c.    
     The print information acquired from the management patches  42 , and the color information obtained by colorimetrically measuring the color chart  34   p  or  34   c  (the color patches  36  shown in  FIG. 2  or  3 ) to which management patches  42  have been added, may be correlated with each other and managed. For example, if the management patches  42  are colorimetrically measured in conjunction with the color patches  36  of the profile color chart  34   p  (see  FIG. 2 ), then it is possible to generate a print profile correlated to the print information of the profile color chart  34   p.  The print profile can thus be reliably managed without error. 
     Since the color association table associates print information directly with the color values, print information can be acquired independently of the plotted (recorded) contents of the print  34 . Furthermore, since the data converter  98  includes the association table generator  100  for generating a color association table depending on the gamut  110  of the printing machine  18 , the color values can appropriately be associated with each other, within a range reproducible by the printing machine  18  and the print information. Even when different types of color charts and prints  34  other than color charts are to be printed, print information of the prints  34  can be acquired without loss of consistency within the same printing machine  18 . 
     Robustness of the printing system  10  as a print information acquiring system can be increased by taking the following items into account: 
     1. Colorimetric Measurement of Management Patches in View of Dry-Down 
     A process for colorimetrically measuring the management patches  42  in view of dry-down, which is caused after the management patches  42  are printed by the printing machine  18 , will be described below. 
       FIG. 9  is a graph illustrating time-dependent changes in color differences in the print  34 , which are caused by dry-down. More specifically,  FIG. 9  shows time-dependent changes in color differences between solid images of the respective process colors C, M, Y, K. The graph includes a horizontal axis representing the time (min.) that has elapsed after production of the print  34 , and a vertical axis representing the color differences (dE) from color values under a steady dry-down. As shown in  FIG. 9 , color differences between the colors C, M, Y, K are exponentially changed immediately after the print  34  is produced, until finally the color differences reach a steady state, i.e., a value of 0 on the vertical axis. 
     Since the color values of the management patches  42  in a steady state can be predicted according to the graph shown in  FIG. 9 , various processing specifications can be realized as described below. 
       FIGS. 10A and 10B  are functional block diagrams showing processing details of the time manager  74  shown in  FIG. 4 . 
       FIG. 10A  shows the flow of time data upon notification of a color chart printing request. As shown in  FIG. 10A , notification of a print request for printing a color chart, e.g., the profile color chart  34   p,  is sent from a controller, not shown. The notification is received by a time acquirer (colorimetric measurement time acquirer, printing time acquirer)  120 , which acquires a present time T=T 1 . Thereafter, the present time T 1  is supplied as the printing time T 1 , as part of the print information that is sent to the encoding processor  102 . 
       FIG. 10B  shows the flow of time data upon notification of completion of a colorimetric measurement performed by the colorimeter  20 . As shown in  FIG. 10B , notification of completion of the colorimetric measurement is sent from a controller, not shown. This notification is received by the time acquirer  120 , which acquires a present time T=T 2 . Thereafter, the present time T 2  is supplied as a colorimetric measurement time T 2  to an elapsed period calculator  122 . 
     The printing time T 1 , which forms part of the print information, is decoded by the decoding processor  104  and supplied to the elapsed period calculator  122 . The elapsed period calculator  122  calculates a difference between the present time (colorimetric measurement time) T 2  and the printing time T 1 . The difference represents an elapsed period ΔT after the management patches  42  have been printed by the printing machine  18  and until the management patches  42  are measured colorimetrically. 
     The elapsed period ΔT is supplied to a warning section  124 , which compares the elapsed period ΔT with preset threshold values, including a first threshold value and a second threshold value. If the elapsed period ΔT is equal to or smaller than the first threshold value, then a display controller, not shown, displays a warning image on the display device  24 . If the elapsed period ΔT is equal to or smaller than the second threshold value (the second threshold value is smaller than the first threshold value), then the display controller displays on the display device  24  a message indicating inhibition of data acquisition from the colorimeter  20 . At this time, the color manager  70  does not use the measured results, i.e., the color values of the color patches  36 , or the management patches  42  acquired during the elapsed period ΔT. 
     The elapsed period ΔT is supplied to the profile generator  94  and used to predict color values L*, a*, in a steady state of the profile color chart  34   p.    
     Specifically, even when colors of the color patches  36  are changed due to dry-down after the profile color chart  34   p  has been printed, the profile generator  94  can estimate and generate a print profile after elapse of a sufficient period of time following printing of the profile color chart  34   p,  using the color values L*, a*, b* acquired by the colorimeter  20  and the supplied elapsed period ΔT. Since the colorimeter  20  can measure color values without requiring any waiting time, operation efficiency is increased. 
     Similarly, the elapsed period ΔT, which is calculated by the elapsed period calculator  122 , is supplied to the predictor  109  and is used to predict color values L*, a*, in a steady state of the management patches  42 . Reading accuracy at which the management patches  42  are read can thus be increased. 
     For calculating the elapsed period ΔT more strictly, a time at which the image data of the color charts are transferred from the image processing apparatus  16  to the printing machine  18  may be defined as the printing time T 1 . In this case, since the transfer time cannot directly be incorporated into the management patches  42 , the transfer time may be stored separately in the storage unit  82  of the image processing apparatus  16 , and may be read therefrom when necessary. 
     A time acquisition patch may be provided, which serves as a trigger for acquiring the colorimetric measurement time T 2  from the management patches  42 . For example, the head patch  42   a  or the tail patch  42   d  may function as such a time acquisition patch. Alternatively, such a time acquisition patch may be provided in addition to the management patches  42  shown in  FIGS. 2 and 3 . 
     A third threshold value for determining whether or not the density of the management patches  42  is capable of being measured may be provided. The third threshold value may be identical to or different from the first or the second threshold value for determining the density of color patches  36  of the profile color chart  34   p  or the density of color patches  36  of the designated color adjusting color chart  34   c.    
     Since the printing time T 1  is acquired for the management patches  42 , the management patches  42  are colorimetrically measured, the colorimetric measurement time T 2  for the management patches  42  is acquired, and the elapsed period ΔT after the management patches  42  are printed and until they are colorimetrically measured is calculated based on the acquired printing time T 1  and the acquired colorimetric measurement time T 2 , the elapsed period ΔT can automatically be acquired. Consequently, even if the management patches  42  are colorimetrically measured while the density thereof is changed due to dry-down, the print information represented by the color values of the management patches  42  can properly be recognized, and hence can appropriately be acquired. 
     2. ID Management for a Plurality of Printing Machines 
     Actually, the printing system  10  can have a plurality of printing machines  18 , which are connected respectively to one image processing apparatus  16 . Insofar as print information has to be managed for each of the printing machines  18 , in principle, the amount of data to be managed by the printing system  10  overall is enormous. If a plurality of printing machines  18  of one type are connected to the image processing apparatus  16 , then the same print information is managed individually for each of such printing machines, and in reality, the management of such print information is quite redundant. 
     Therefore, it is preferable to manage the print information uniformly based on ID numbers, which are defined commonly for a plurality of printing machines  18 . 
     Specifically, ID numbers defined commonly for a plurality of printing machines  18  are established. A first association table, which associates given color values (colors in an overlapping area of gamuts) with the ID numbers, is generated. Also, a second association table, which associates the ID numbers with the print information for each of the printing machines  18 , is generated, thereby associating the colors of the management patches  42  with the print information. 
       FIG. 11  is a graph showing a positional relationship between gamuts of two printing machines  18 . For illustrative purposes, the two printing machines  18  will hereinafter be referred to as a first printing machine  18   a  and a second printing machine  18   b.    
     The graph shown in  FIG. 11  represents an H*-axis cross-sectional view of an L*C*H* space, having a horizontal axis representing a C*-axis, and a vertical axis representing an L*-axis. An area surrounded by the solid lines represents a gamut  150  of the first printing machine  18   a,  and an area surrounded by the dot-and-dash lines represents a gamut  152  of the second printing machine  18   b.    
     The gamut  150  and the gamut  152  have an overlapping area  154 . Since both the first printing machine  18   a  and the second printing machine  18   b  can reproduce colors in the overlapping area  154 , common ID numbers (global ID numbers) can be used for the overlapping area  154 . A differential, which is set between the gamut  150  and the overlapping area  154 , is referred to as a non-overlapping area  156 . Since only the first printing machine  18   a  can reproduce colors in the non-overlapping area  156 , ID numbers (private ID numbers) unique to the first printing machine  18   a  are used for the non-overlapping area  156 . A differential, which is set between the gamut  152  and the overlapping area  154 , is referred to as a non-overlapping area  158 . Since only the second printing machine  18   b  can reproduce colors in the non-overlapping area  158 , ID numbers (private ID numbers) unique to the second printing machine  18   b  are used for the non-overlapping area  158 . 
     Global ID numbers are assigned to colors in the overlapping area  154 , and private ID numbers are assigned to colors in the non-overlapping areas  156  and  158 . Consequently, one private ID number can be assigned to one color in the non-overlapping area  156 , and to one color in the non-overlapping area  158 . In other words, different printing conditions can be assigned respectively to the printing machines  18 . 
       FIG. 12  is a diagram illustrating a process of setting ID numbers for three printing machines  18 . For illustrative purposes, the three printing machines  18  will hereinafter be referred to as a first printing machine  18   a,  a second printing machine  18   b,  and a third printing machine  18   c.    
     In  FIG. 12 , substantially circular gamuts  160 ,  162 ,  164 , which are indicated by solid lines, belong to the first printing machine  18   a,  the second printing machine  18   b,  and the third printing machine  18   c,  respectively. 
     The gamuts  160 ,  162 ,  164  have an overlapping area  166 . Since all of the three printing machines, i.e., the first printing machine  18   a,  the second printing machine  18   b,  and the third printing machine  18   c,  can reproduce colors in the overlapping area  166 , common ID numbers (global ID numbers) can be used for the overlapping area  166 . In  FIG. 12 , ID numbers  1  through  10  are assigned to the overlapping area  166 . 
     The gamuts  160 ,  162  have a partial overlapping area  168 . Since the first printing machine  18   a  and the second printing machine  18   b  can reproduce colors in the partial overlapping area  168 , ID numbers (private ID numbers) common to the first printing machine  18   a  and the second printing machine  18   b  are used for the partial overlapping area  168 . In  FIG. 12 , ID numbers  11  through  20  are assigned to the partial overlapping area  168 . 
     The gamuts  160 ,  164  have a partial overlapping area  170 . Since the first printing machine  18   a  and the third printing machine  18   c  can reproduce colors in the partial overlapping area  170 , ID numbers (private ID numbers) common to the first printing machine  18   a  and the third printing machine  18   c  are used for the partial overlapping area  170 . In  FIG. 12 , ID numbers  21  through  30  are assigned to the partial overlapping area  170 . 
     The gamuts  162 ,  164  have a partial overlapping area  172 . Since the second printing machine  18   b  and the third printing machine  18   c  can reproduce colors in the partial overlapping area  172 , ID numbers (private ID numbers) common to the second printing machine  18   b  and the third printing machine  18   c  are used for the partial overlapping area  172 . In  FIG. 12 , ID numbers  31  through  40  are assigned to the partial overlapping area  172 . 
     A differential, which is set between the gamut  160 , the overlapping area  166  and the partial overlapping areas  168 ,  170 , is referred to as a non-overlapping area  174 . Since only the first printing machine  18   a  can reproduce colors in the non-overlapping area  174 , ID numbers (private ID numbers) unique to the first printing machine  18   a  are used for the non-overlapping area  174 . In  FIG. 12 , ID numbers  31  through  50 , which have not been assigned to the first printing machine  18   a,  are assigned to the non-overlapping area  174 . 
     A differential, which is set between the gamut  162 , the overlapping area  166  and the partial overlapping areas  168 ,  172 , is referred to as a non-overlapping area  176 . Since only the second printing machine  18   b  can reproduce colors in the non-overlapping area  176 , ID numbers (private ID numbers) unique to the second printing machine  18   b  are used for the non-overlapping area  176 . In  FIG. 12 , ID numbers  21  through  30  and  41  through  50 , which have not been assigned to the second printing machine  18   b,  are assigned to the non-overlapping area  176 . 
     A differential, which is set between the gamut  164 , the overlapping area  166  and the partial overlapping areas  170 ,  172 , is referred to as a non-overlapping area  178 . Since only the third printing machine  18   c  can reproduce colors in the non-overlapping area  178 , ID numbers (private ID numbers) unique to the third printing machine  18   c  are used for the non-overlapping area  178 . In  FIG. 12 , ID numbers  11  through  20  and  41  through  50 , which have not been assigned to the third printing machine  18   c,  are assigned to the non-overlapping area  178 . 
     According to the process illustrated in  FIG. 12 , it is possible to uniformly manage common ID numbers, and thus the amount of data involved can be reduced. Other management of data, such as registration and deletion of data, can also be facilitated. 
     Specifically, as shown in  FIG. 12 , if 50 items of print information are managed for each of the three printing machines, it has heretofore been necessary to manage a total of 150 colors for the three printing machines. 
     According to the present embodiment, however, it is only necessary to manage a total of 100 colors for the three printing machines. 
     If the printing system  10  includes a plurality of image processing apparatus  16 , then respective management apparatus therefor may be provided separately, depending on the types of ID numbers used. For example, global ID numbers may be managed uniformly by the database DB connected to the LAN  12  (see  FIG. 1 ). Private ID numbers assigned to the respective printing machines  18  may be managed individually by the respective image processing apparatus  16  (the color ID manager  96  shown in  FIG. 4 ), which are connected to the printing machines  18 . 
     3. Prediction of Color Values of a Print After the Print is Covered With a Protective Film 
     If a protective film, such as a laminating film, is applied to the image forming surface of the print  34 , then the color values of a color image on the print  34  may be changed in a non-negligible manner before and after the laminating film is applied. A print with a protective film applied thereto will be referred to as a “protective-film-applied print”. 
     Usually, the color patches  36  of the profile color chart  34   p,  which is free of a protective film, are colorimetrically measured in view of better operation efficiency and economy. However, it may be necessary to measure the management patches  42  in order to reconfirm the print information after the designated color adjusting color chart  34   c  has been covered with a protective film and the designated color is adjusted in color. In such a case, inasmuch as different color values are produced before and after the laminating film is applied, it is possible that the print information encoded by the management patches  42  will not be acquired properly. However, once the protective film is applied, it is virtually impossible, or highly difficult, to peel the applied protective film off from the print  34 . 
     To solve this problem, the acquired color values of the management patches  42  may be corrected depending on whether a protective film is present or not, and also depending on the type of protective film, and then the acquired color values are decoded into print information. In this manner, the color values of the management patches  42  can properly be decoded irrespective of whether the management patches  42  are colorimetrically measured before or after the print  34  has been covered with a protective film. 
     Alternatively, the color values that are encoded from the print information may be corrected in advance depending on whether or not the protective film is present, and also depending on the type of protective film utilized when the management patches  42  are colorimetrically measured. In this manner, color values of the management patches  42  can properly be decoded, irrespective of whether the management patches  42  are colorimetrically measured before or after the print  34  has been covered with the protective film. 
     4. Process of Printing Management Patches 
     If the printing machine  18  is an ink jet printer, then as the amount of inks applied to the print medium  32  becomes greater, it takes longer for the applied inks in the print medium  32  and on the surface of the print medium  32  to dry sufficiently. In addition, if the applied inks exceed an allowable amount that can be absorbed by the print medium  32  or an allowable rate at which the applied inks can be absorbed by the print medium  32 , then the surface of the print medium  32  may possibly cause overflowing of the inks. If the management patches  42  are colorimetrically measured before elapse of a sufficient drying period after images have been formed on the print medium  32 , then the following drawbacks tend to occur: 
     If the colorimeter  20  or the operator mistakenly touches the print medium  32  exhibiting ink overflow at a certain location thereon, then since the inks become applied to the colorimeter  20  or the operator, the location on the print  34  is liable to become discolored or to exhibit mixed coloration. In addition, since the abrasion resistance of the surface of the print medium  32  is reduced when the applied inks are not dried sufficiently, the surface of the print  34  may develop scratch marks therein. In either case, the print  34  tends to be subjected to a printing failure, and may lead to malfunctioning of the colorimeter  20 . 
     To avoid the above difficulties, color values of the management patches  42  may be selected depending on the ink amounts used to print the management patches  42 . Accordingly, the ink amounts to be used can be recognized in advance, and variations in the printed density due to dry-down can be estimated. 
     Color values of the management patches  42  may be selected such that the total amount of color inks used to print the management patches  42  will be smaller than the total amount of color inks used to print a print area (images, characters, etc.) of the print medium  32  other than the management patches  42 . The surface of the print medium  32  where the management patches  42  are printed is thus prevented from suffering from ink overflow, so that the time required for the inks to dry can be shortened. Moreover, variations in the printed density due to dry-down can also be reduced. 
       FIGS. 13A and 13B  are conceptual diagrams showing examples of determining ink amounts used to print management patches. In  FIGS. 13A and 13B , three ink colors C, M, Y (or C, M, K) are shown for illustrative purposes. However, the number of ink colors and the combinations thereof can be changed as desired. 
       FIG. 13A  shows an example of determining the amounts of C, M, Y inks, which are water-based inks that are soluble by a solvent mainly composed of water. In  FIG. 13A , each of a C-axis, an M-axis, and a Y-axis represents a halftone dot percentage (corresponding to a range from 0% to 100% in terms of the ejected amount of ink), which is set in a range from 0% to 100%. In  FIG. 13A , a region  200  is provided in the shape of a triangular pyramid having a plane defined by three points (C, M, Y)=(70, 0, 0), (0, 70, 0), (0, 0, 70) and a vertex at the origin O. The total amount of C, M, Y inks can be 70% or smaller at all times, using any desired colors within the region  200 . 
       FIG. 13B  shows an example of determining the amounts of C, M, Y inks, which are pigment-based inks that a soluble by a solvent mainly composed of an organic solvent. In  FIG. 13B , each of a C-axis, an M-axis, and a Y-axis represents a halftone dot percentage (corresponding to a range from 0% to 100% in terms of the ejected amount of ink), which is set in a range from 0% to 100%. In  FIG. 13B , there is provided a region  202  in the shape of a heptahedron defined by removing three small triangular pyramids having respective vertexes at (C, M, Y)=(150, 0, 0), (0, 150, 0), (0, 0, 150) from a larger triangular pyramid shown by the broken lines. The total amount of C, M, Y inks can be 150% or smaller at all times, using any desired colors within the region  202 . 
     The printing machine driver  66  (see  FIG. 4 ) converts C, M, Y, K data corresponding to color values of the management patches  42  into appropriate ink propulsion control data. A color conversion LUT of the printing machine driver  66  may be referred to, and only color values that reduce the amount of inks used when the printing machine  18  produces prints may be selected in advance. 
     The above process of printing the management patches  42  also is applicable when standard inks of colors C, M, Y, K (process colors), optional inks of light colors such as LC, LM, etc., and achromatic colors such as white and clear are used. For minimizing the amount of inks to be used as well as widening the color reproduction range within the gamut  110 , for example, light color inks and achromatic color inks may not be used, whereas inks of dark colors such as process colors mainly may be used. 
     If the printing machine  18  is capable of controlling the ejected ink amounts so as to form ink dots on the print medium  32  in a plurality of ink dot sizes or diameters, then the ejected ink amounts may be selected in order to widen the color reproduction range. For example, an image may be formed in which the ink dot diameters are increased in order to increase the color reproduction range of L* (especially shadows). 
     Furthermore, for making the density at which the color inks are applied to the print medium  32  uniform, the printing machine driver  66  may generate ink propulsion control data in order to allocate ink droplets (amounts), which are microscopically equal to the print medium  32 . 
     A printing period for the print  34  may be estimated based on a print mode in a print area other than the management patches  42 , and the ink amounts used to form the management patches  42  may be determined in view of the estimated printing period. 
       FIG. 14  shows a profile color chart  34   p A, which is a modification of the profile color chart  34   p  shown in  FIG. 2 . The profile color chart  34   p A includes management patches  42  on a leading end  204  of the print medium  32 , i.e., at an upstream end of the print medium  32  with respect to the direction in which the print medium  32  is fed. 
     The print  34 , i.e., the print medium  32 , is held in the printing machine  18  after the printing machine  18  starts to print the print  34  and until the print  34  is printed completely down to a trailing end  206  thereof, i.e., until the print area (the color patches  36  in  FIG. 14 ) is printed in its entirety. When the print medium  32  is cut off and the print  34  is discharged from the printing machine  18 , a considerable period of time has elapsed since printing of the management patches  42 . As can be seen from the density variation characteristics (see  FIG. 9 ) of the print  34 , due to dry-down, variations in the printed density of the management patches  42  are reduced by the time the management patches  42  can be colorimetrically measured. 
     With the management patches  42  positioned on the leading end  204  of the print medium  32 , i.e., the end of the print medium  32  that initially is printed, the period of time (elapsed time ΔT) from the printing time T 1  to the colorimetric measurement time T 2  is increased. As a result, the process of decoding the management patches  42  is increased in accuracy, despite variations in the printed density due to dry-down. 
     The present invention is not limited to the above embodiment. Various changes and modifications can be made without departing from the scope of the invention, as described below. 
     In the illustrated embodiment, the profile color chart  34   p  (see  FIG. 2 ) has 100 color patches  36 , while the designated color adjusting color chart  34   c  (see  FIG. 3 ) has 49 color patches. However, the profile color chart  34   p  and the designated color adjusting color chart  34   c  may have different numbers of color patches. 
     In the illustrated embodiment, the profile color chart  34   p  and the designated color adjusting color chart  34   c  are illustrated by way of example. However, other types of color charts may be printed. For example, a color chart may be printed, which can be presented to a client for final confirmation of a designated color. 
     In the illustrated embodiment, a single image processing apparatus  16  operates to perform various functions to (1) encode print information, (2) instruct the printing machine  18  to produce a print, (3) acquire colorimetric data, (4) decode management patches, and (5) acquire print information. However, a plurality of respective apparatus may be used to perform the above functions. For example, the color association table of the printing machine  18  may uniformly be managed by the database DB. In such a case, color values of the management patches  42 , which are acquired by the colorimeter  20 , are sent from the image processing apparatus  16  to the database DB, which converts the color values into print information of the print  34 . In this manner, the image processing apparatus  16  can acquire print information of the print  34  without the need for the decoding processor  104 . 
     In the illustrated embodiment, the printing machine  18  comprises an ink jet printer. However, the printing machine  18  may comprise an offset printing press, an electrophotographic printer, a thermosensitive printer, or the like. 
     Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made to the embodiments without departing from the scope of the invention as set forth in the appended claims.