JP4251053B2 - Gradation adjustment system, gradation adjustment method, and gradation adjustment system control program - Google Patents

Description

  The present invention relates to a gradation adjustment system, a gradation adjustment method, and a gradation adjustment system control program for an image forming apparatus, and in particular, a technique for realizing a suitable gradation when the maximum density that can be formed by the image forming apparatus is reduced. About.

  An image forming apparatus (such as a copying machine or a printer) that forms an image based on image data controls the amount of toner, the amount of ink, and the like based on the image data. Tones are generated. For example, in an electrophotographic image forming apparatus, the amount of toner adhering to a latent image is controlled by controlling the intensity of laser light that forms a charged latent image on a photoreceptor, thereby generating gradation on the medium. Is done. In order to perform this control, the image forming apparatus defines a correspondence relationship (reference gradation characteristic) between image data (input value) and a target density (output value) that is a target value of density formed on the medium. Has a conversion table. For example, in an image forming apparatus that forms an image using toners of four colors of cyan (C), magenta (M), yellow (Y), and black (K), a reference gradation characteristic is set for each CMYK component. Is done. Then, using the reference gradation characteristics for each color component, each color component value of the image data is converted to a target density for each color component, and based on control conditions such as laser light intensity determined according to the target density. Thus, the amount of toner fixed on the medium is controlled as described above.

  However, even if an attempt is made to control each part of the image forming apparatus under a predetermined condition, the density of the image actually formed on the medium is not necessarily constant due to the influence of the usage environment and changes in the components over time. The target concentration is not always achieved. For this reason, the image forming apparatus conventionally holds a gradation correction table, adjusts the density of the image on the medium based on the table, and performs a calibration process to bring it closer to the target density. In order to obtain corrected data to be stored in the gradation correction table, a patch chart is formed on the medium by the image forming apparatus based on the reference image data in which a predetermined gradation pattern is represented, and the patch chart is displayed. The gradation pattern image is converted again into image data by an image reading device such as a scanner. Then, based on the output image data, correction data that cancels the difference in the output image data with respect to the input reference image data is obtained, and stored in the gradation correction table.

  FIG. 6 is a schematic graph showing the relationship between the image data and the actual density printed on the patch chart. The horizontal axis represents the image data, and the vertical axis corresponds to the density. Here, the image data is binary data of 8 bits and takes a value in the range of 0 to 255. On the other hand, the vertical axis is an arbitrary scale. In the figure, in addition to the gradation curve 2 corresponding to the reference gradation characteristic, the gradation curve 4 when an image is formed with a darker density than that indicated by the reference gradation characteristic at each data value, and A gradation curve 6 in the case where an image is formed with a darker density than that indicated by the reference gradation characteristics at each data value is illustrated.

  The reference gradation characteristic is basically expressed by curve 2, and the larger the data value, the higher the density, and the density change rate at each data value is determined so that suitable gradation expression is realized. It is done. In addition, the maximum density of the normal reference gradation characteristics is set as an upper limit value of capability in the standard environment and use conditions of the image forming apparatus.

  By the image formation and reading using the reference image data, the function PD (x) of the data value x is obtained for the actually formed density. This means that if the reference gradation curve 2 given by the reference gradation characteristic is a function TD (x), the density TD (x1) is obtained at a certain data value x1, but PD (x1) is actually obtained. That is. Here, if PD (x1) is equal to TD (x1), an image may be formed under the control conditions defined for the reference gradation characteristics. On the other hand, when PD (x1) is different from TD (x1), the data value x1 is corrected (calibrated) so that the density TD (x1) is obtained on the medium. For example, when the value PD (x2) of PD (x) at the data value x2 is equal to TD (x1), the gradation correction table stores the corrected data x2 with respect to the data value x1. . In this way, the image forming apparatus performs output processing on the data value x2 obtained by converting the input data value x1, so that the density PD (x2), that is, TD (x1) is realized on the medium.

FIG. 7 shows a schematic graph of the gradation correction curve stored in the gradation correction table for each gradation curve shown in FIG. 6, with the horizontal axis representing the input image data and the vertical axis representing the corrected image. Represents data. The maximum value on the vertical axis is 255, and when the maximum density TDmax of the reference gradation matches the current maximum density PDmax of the image forming apparatus, the maximum value PD is associated with the input data value 255. If the current gradation characteristic of the image forming apparatus matches the reference gradation characteristic 2, the gradation correction curve 12 is a straight line corresponding to no conversion. For the gradation curve 4 that gives a dark density, a gradation correction curve 14 that gives a smaller value than the gradation correction curve 12 in each data value is generated. On the other hand, for the gradation curve 6 that gives a light density, a gradation correction curve 16 that gives a value larger than the gradation correction curve 12 in each data value is generated. However, the gradation correction curve 16 reaches the maximum value 255 at a point Ds before the upper limit of the input data value.
JP 07-264427 A

  Some image forming apparatuses can be adjusted so as to increase the maximum density of an image to be formed, as shown in Patent Document 1 above. However, an image forming apparatus that does not have such an adjustment function uses a standard environment and a usage for the upper limit of the data value as described above in the process of forming a gradation pattern image using the reference image data. It is set so as to give the density of the upper limit of capacity in the conditions. That is, the maximum density of the gradation pattern image formed by the processing is the maximum density that the image forming apparatus can actually realize at present. Therefore, when the current maximum density PDmax of the image forming apparatus is lower than the maximum density TDmax of the reference gradation, gradation correction data that realizes a density exceeding PDmax cannot be defined. In FIG. 7, the horizontal portion 16 ′ appearing in the gradation correction curve 16 on the upper limit side (D ≧ Ds) of the data value D represents this, and the horizontal portion where the gradation correction data value is maintained at the upper limit value 255. At 16 ', the density realized on the medium is a constant value PDmax. FIG. 8 is a schematic graph showing the gradation characteristics after calibration when the current maximum density PDmax of the image forming apparatus is lower than the maximum density TDmax of the reference gradation. The horizontal axis represents image data, and the vertical axis represents image data. Represents the concentration. The characteristic represented by the solid line is the gradation curve 20 after calibration, and the dotted line is the reference gradation curve 12 shown for comparison. The gradation curve 20 is corrected so as to coincide with the reference gradation curve 12 below the data value Ds, but in the range exceeding Ds, the density becomes a constant value PDmax, and the maximum value of the reference gradation characteristic at the upper limit of the data value TDmax is not reached. As described above, when PDmax <TDmax, a saturation region in which the density is kept constant occurs on the upper limit side of the data value of the gradation characteristic even after calibration. For this reason, in an image forming apparatus that does not have a means for adjusting the maximum density that can be realized, it has been impossible to avoid the problem that no gradation difference occurs in the area, that is, the gradation is lost.

  The present invention solves this problem, and is a gradation adjustment system, a gradation adjustment method, and a gradation adjustment system that realize a suitable gradation even when the maximum density that can be formed by the image forming apparatus is reduced. An object is to provide a control program.

  A gradation adjustment system according to the present invention performs gradation adjustment on an image forming apparatus that forms an image based on a reference gradation characteristic that defines a correspondence relationship between an input value of image data and a target density for image formation. A reference image input unit that inputs reference image data representing a gradation to the image forming apparatus, a density measuring unit that measures a density of a formed image of the image forming apparatus with respect to the reference image data, and Based on the measurement result of the density measuring means, an image forming density upper limit detecting means for detecting the upper limit value of the image forming density by the image forming apparatus, and a new reference floor according to the image forming density upper limit value of the image forming apparatus. Tone characteristic generating means for generating tone characteristics.

  Another gradation adjustment system according to the present invention generates an image composed of a plurality of component colors based on a reference gradation characteristic that defines a correspondence relationship between a color component value of image data and a target density of image formation for the color. A reference image input unit that performs gradation adjustment on the image forming apparatus, and that inputs reference image data representing a gradation for each of the component colors to the image forming apparatus, and the reference image data A density measuring unit that measures the density of a formed image of the image forming apparatus with respect to the image, and an image that detects an upper limit value of the density of image formation of each component color by the image forming apparatus based on a measurement result of the density measuring unit Forming density upper limit detecting means; and tone characteristic generating means for generating a new reference tone characteristic for each component color in accordance with the image forming density upper limit value of each component color of the image forming apparatus.

  Still another gradation adjustment system according to the present invention is intended for a plurality of image forming apparatuses, and the reference image input means inputs the reference image data common to the image forming apparatuses, The gradation characteristic generation unit generates a new reference gradation characteristic common to the plurality of image forming apparatuses in accordance with a minimum value among the image formation density upper limit values of the image forming apparatuses.

  In these preferred embodiments of the present invention, the gradation characteristic generation unit generates the new reference gradation characteristic when the image formation density upper limit is smaller than the current maximum density of the reference gradation characteristic. Adjustment system.

  Another gradation adjustment system according to the present invention generates an image composed of a plurality of component colors based on a reference gradation characteristic that defines a correspondence relationship between a color component value of image data and a target density of image formation for the color. A reference image input unit that performs gradation adjustment on the image forming apparatus, and that inputs reference image data representing a gradation for each of the component colors to the image forming apparatus, and the reference image data A density measuring unit that measures the density of a formed image of the image forming apparatus with respect to the image, and an image that detects an upper limit value of the density of image formation of each component color of the image forming apparatus based on a measurement result of the density measuring unit A formation density upper limit detection unit; a representative color selection unit that selects one representative color from the plurality of component colors based on an image formation density upper limit value of each component color of the image forming apparatus; First gradation characteristic generation means for generating a new reference gradation characteristic of the representative color in accordance with an image formation density upper limit value of the representative color of the forming apparatus; a current reference gradation characteristic of the representative color; Based on the relative relationship with the current reference gradation characteristics of the component colors other than the representative color, the new reference gradation characteristics of the component colors other than the representative color are changed from the new reference gradation characteristics of the representative color. Second gradation characteristic generating means for generating.

  In a preferred aspect of the present invention, the representative color selecting unit selects the representative color based on a relative magnitude of an image formation density upper limit value with respect to a current maximum density of the reference gradation characteristic for each component color. This is a gradation adjustment system to be selected.

  Another gradation adjustment system according to the present invention includes a gradation characteristic storage unit that stores the reference gradation characteristic generated in the past, and the reference gradation characteristic stored in the gradation characteristic storage unit. Gradation characteristic setting means for setting the image selected by the user in the image forming apparatus.

  A gradation adjustment method according to the present invention performs gradation adjustment on an image forming apparatus that forms an image based on a reference gradation characteristic that defines a correspondence relationship between an input value of image data and a target density for image formation. A reference image input step for inputting reference image data representing a gradation to the image forming apparatus, a density measurement step for measuring a density of a formed image of the image forming apparatus with respect to the reference image data, and An image formation density upper limit detecting step for detecting an upper limit value of image formation density by the image forming apparatus based on a measurement result in the density measurement step, and a new reference according to the image formation density upper limit value of the image forming apparatus A gradation characteristic generation step for generating gradation characteristics.

  A gradation adjustment system control program according to the present invention performs gradation adjustment on an image forming apparatus that forms an image based on a reference gradation characteristic that defines a correspondence relationship between an input value of image data and a target density for image formation. A computer that controls a gradation adjustment system to be performed, a reference image input procedure for inputting reference image data representing gradations to the image forming apparatus, and a density of a formed image of the image forming apparatus with respect to the reference image data is measured. A density measurement procedure to be performed, an image formation density upper limit detection procedure for detecting an upper limit value of the density of image formation by the image forming apparatus based on a measurement result in the density measurement procedure, and an image formation density upper limit of the image forming apparatus A gradation characteristic generation procedure for generating a new reference gradation characteristic according to the value is executed.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. Here, a mode of adjusting the gradation of each component color realized by printing with a color printer is shown, but the adjustment target device may be another image forming device that forms an image on a medium such as a multifunction peripheral. it can. FIG. 1 is a block diagram showing a schematic configuration of a gradation adjustment system according to the present invention. The system includes a printer 30, a print server 32, a scanner 34, a client computer 36, and a communication network 38 such as a local area network (LAN) that enables data transmission therebetween.

  Here, the printer 30 is a device that performs printing using toners of four colors of CMYK. The client computer 36 issues a print instruction to the print server 32 based on a user operation. The print server 32 accumulates the image data requested to be printed by, for example, the client computer 36 via the communication network 38 or the like, and sets the schedule to send the image data to the printer 30 for printing. In particular, in this system, the print server 32 has a function of inputting reference image data representing a patch chart including a predetermined gradation pattern to the printer 30. A gradation pattern is provided for each color of CMYK. Here, the patch chart may be displayed by changing the page for each color, or one page may include gradation patterns of all colors. The print server 32 also has a function of performing arithmetic processing related to gradation adjustment and generating new reference gradation characteristics as will be described later. The scanner 34 is a color scanner provided for measuring the density of the gradation pattern image of each color on the patch chart printed on the medium by the printer 30 based on the reference image data. Convert to data. Here, the image data corresponds to the density measurement result of the printed image. The print server 32 detects the upper limit value of the current print density of the printer 30 for each color based on the image data.

  FIG. 2 is a schematic process flow diagram of gradation adjustment using this system. The gradation adjustment is started when the user sends an instruction from the client computer 36 to the print server 32 (S50). When the print server 32 receives an instruction to perform gradation adjustment from the client computer 36, the print server 32 inputs the reference image data to the printer 30, and the printer 30 prints a patch chart based on the reference image data (S55).

  The user sets the printed patch chart on the scanner 34, and instructs the scanner 34 to read from the client computer 36 (S60). The scanner 34 reads the patch chart to generate RGB image data, inputs it to the client computer 36, and the client computer 36 transfers the image data to the print server 32 (S65). The RGB image data is converted into CMYK color components by the print server 32, and density information for each CMYK color of the gradation pattern shown in the patch chart is obtained. The print server 32 compares the current maximum density PDmax of the printer 30 obtained from the patch chart reading result with the maximum density TDmax of the reference gradation characteristics currently set in the printer 30 for each color of CMYK (S70). According to the comparison result and the user's instruction, one of several prepared gradation adjustment contents is selected (S75) and executed (S80).

  FIG. 3 is a schematic process flow diagram of selection of adjustment contents (S75) and execution (S80). The print server 32 compares the current maximum density PDmax and the maximum density TDmax of the reference gradation characteristics for each color. As a result, if PDmax ≧ TDmax for any color (for example, the reference floor shown in FIG. 6 for each color). When the gradation actually obtained for the tone curve 2 is the curve 4 (S100), the normal calibration process described above as the prior art is executed for each color (S105).

For example, the process S105 for cyan (C) will be specifically described. The data value of C is represented by x, the density is represented by n, the function of the reference gradation curve 2 is n = TD _C (x), and the function n = PD _C (x) of the gradation curve (for example, curve 4) obtained at present. The inverse function is expressed as x = PD _C ⁻¹ (n). If the PD _C as described above _(x2) is equal to TD _{C (x1)} is the gradation correction table C for the data values x1, the data x2 is stored as corrected data x '. That is, a gradation correction table in which data x ′ given by the following equation is stored for an arbitrary data value x is generated.

x ′ = PD _C ⁻¹ (TD _C (x)) (1)

Other colors M, Y, function TD _M reference gradation curve 2 also _{K (x), TD Y (} x), TD K (x), and the function of the gradation curve of the current obtained from the measurement of the patch chart _{PD M (x), PD Y} (x), on the basis of the PD _{K (x),} the gradation correction table for each color is generated.

  On the other hand, for any color, when the current maximum density PDmax is lower than the maximum density TDmax of the reference gradation characteristic, that is, when PDmax <TDmax (S100), the three processing contents S110, S115, and S120 Any one of them is selected based on a user instruction (S125) and executed. Further, prior to selection / execution of the processing, the print server 32 obtains the difference (TDmax−PDmax) for the color satisfying PDmax <TDmax, and when the difference exceeds a predetermined threshold AL (S130). ), Warning processing for the user is executed (S135).

  In this warning process, for example, a warning is displayed on the display of the print server 32 or the client computer 36. The content of the warning display may include information about what color the density decrease is occurring and the degree of the color. Further, when the degree is equal to or greater than a predetermined value, an instruction for calling maintenance personnel or prompting parts replacement can be issued. Further, PDmax and the like in the past gradation adjustment may be stored, and a condition for issuing a warning and a warning content may be changed based on the tendency of the change. Note that the user can specify settings such as whether to perform warning processing when the AL setting or difference reaches AL.

  Hereinafter, the gradation adjustment processing S110 that emphasizes fidelity, the gradation adjustment processing S115 that emphasizes gradation, and the gradation adjustment processing S120 that emphasizes color balance will be described.

  First, in the fidelity-oriented process S110, the print server 32 is basically based on the expression (1) for C and based on the same expression for other colors, as in the normal calibration of the process S105. A gradation correction table is generated for each color. However, the density of the color satisfying PDmax <TDmax saturates to the current maximum value PDmax on the upper limit side (D> Ds) of the data value D as described in the problem of the prior art. As a result, the density change becomes discontinuous in the vicinity of Ds, which may cause a visually uncomfortable feeling. For this reason, in this system, for a color satisfying PDmax <TDmax, smoothing processing is performed so that the density continuously changes from before Ds to the upper limit value of the data value. For example, a point where Dr <Ds can be set as a parameter, and the density change rate (gradient curve slope) is set with boundary values of the value and slope of the reference gradation curve at Dr and the density PDmax at D = 255. The smoothing function can be defined such that decreases linearly from Dr to 255. In this fidelity-oriented process, the reference gradation characteristics initially set in the printer 30 are set for the color whose density is not saturated over the entire range of data values, and for the color whose density is saturated, for example, in the range of 0 to Dr. Based faithful gradation is realized.

  FIG. 4 is a schematic graph showing an example of a new reference gradation characteristic obtained by the fidelity emphasis process S110. The horizontal axis represents image data, and the vertical axis corresponds to density. A dotted line 150 represents a new reference gradation characteristic for a color whose density is not saturated. On the other hand, a solid line 152 is a new reference gradation characteristic for a color whose density is saturated.

In the gradation-oriented process S115, the print server 32 performs conversion by multiplying the current reference gradation characteristic TD (x) by PDmax / TDmax for the color satisfying PDmax <TDmax, and uses the result as a new reference gradation. Characteristic. This new reference gradation characteristic is set in the printer 30 in place of the previous reference gradation characteristic and is used for gradation adjustment. For example, PDmax for C, respectively TDmax PD _C max, expressed as TD _C max, PD _C max <TD _C when a max, the reference gradation characteristic TD _{C (x} for C that is currently set ) on the basis of a new reference gradation characteristic TD _{C '(x)} is generated by the following equation.

TD _C ′ (x) = TD _C (x) · PD _C max / TD _C max (2)

On the other hand, become a PDmax <TDmax is not more for the other colors, if for C a PD _C max ≧ TD _C max, the current of the reference gradation characteristic is as it is used. That is, in this case, the result of the gradation-oriented processing S115, TD _C output _'(x) is
TD _C '(x) = TD _C (x) (3)
It becomes.

Here, C has been described as an example, but this processing is performed for each color. That is, for the other colors MYK, they are PDmax for each color PD _M max, PD _Y max, the PD _K max, is TDmax for the respective colors TD _M max, TD _Y max, and TD _K max, the current reference gradation characteristic _{TD M (x), TD Y} (x), by using the TD _{K (x),} in the same manner as for the above _{C TD M '(x),} TD Y' (x), TD _K ′ (x) is generated. In this tone-oriented processing, a new reference tone characteristic TD ′ (x) to be generated is generated by multiplying the original reference tone characteristic TD (x) by a constant coefficient in the entire range of data values. As a result, the density at each data value can be uniformly reduced, but the change in density according to the data value is similar to the original reference gradation characteristic TD (x). Therefore, a good gradation similar to the original reference gradation characteristic can be obtained.

  FIG. 5 is a schematic graph showing an example of a new reference gradation characteristic obtained by the gradation emphasis processing S115, where the horizontal axis represents image data and the vertical axis corresponds to density. A dotted line 160 represents a new reference gradation characteristic for a color whose density is not saturated. On the other hand, a solid line 162 is a new reference gradation characteristic for a color whose density is saturated.

In the color balance emphasizing process S120, consideration is given to maintaining the color balance obtained with the original reference gradation characteristics. That, TD _C at each data value _{'(x), TD M'} (x), TD Y '(x), TD K' mutual ratio of (x) _{is, TD C (x), TD} M (x ), TD _{Y (x),} converted to equal the mutual proportions of the TD _{K (x)} is performed. In this process, a new reference gradation characteristic TD ′ (x) is generated for the reference color by the same conversion as the gradation-oriented process as expressed by the equations (2) and (3). for other colors, this _{TD '(x), TD C} (x), TD M (x), TD Y (x), on the basis of the mutual proportions of the TD _{K (x),} a new reference tone A characteristic TD ′ (x) is generated. For example, the print server 32 selects the color with the highest degree of density reduction as the reference color. This selection is performed based on, for example, input data xr that gives a value corresponding to the current maximum density PDmax on the current reference gradation characteristic TD (x), that is, TD ⁻¹ (PDmax), and gives the smallest xr. Select a color as the reference color.

For example, here, C is the reference color. For C, a new reference gradation characteristic TD _C ′ (x) is obtained by the equations (2) and (3). For other colors, for each data value x:
TD _C '(x) = TD _C (z) (4)
Through a variable z that satisfies
TD _M '(x) = TD _M (z) (5)
TD _Y '(x) = TD _Y (z) ......... (6)
TD _K '(x) = TD _K (z) ......... (7)
To obtain a new reference gradation characteristic. In other words, the equations (5), (6), (7) are
TD _M '(x) = TD _M (TD _C ^-1 (TD _C ' (x))) (8)
TD _Y ′ (x) = TD _Y (TD _C ⁻¹ (TD _C ′ (x))) (9)
_{TD K '(x) = TD} K (TD C -1 (TD C' (x))) ......... (10)
It becomes. The new reference tone characteristics generated for each color are set in the printer 30 and used for tone adjustment instead of the reference tone characteristics of each color so far.

  In this process, the color balance is maintained as described above, and the reference color is set to the color with the highest density reduction rate. Therefore, not only the color but also the new reference gradation characteristics of other colors in the data value upper limit area. Concentration saturation does not occur. On the other hand, when density reduction occurs for a plurality of colors, the density reduction of the entire image may be mitigated using the second or third color reduction rate as a reference color. In that case, for the color with the first reduction rate, the range of data values where density saturation occurs can be reduced, but not completely eliminated. The effect also affects other colors, and in order to maintain the color balance, other colors will also be saturated in the same data value range as the color with the first reduction rate. Unnaturalness can be alleviated by applying the smoothing process already described in the fidelity-oriented process.

  The print server 32 can register and save a new reference gradation characteristic to be generated, and can be configured to be reused later. In the configuration, for example, when the print server 32 generates a new characteristic, it confirms with the user whether or not to register it. Moreover, when registering, it can comprise so that a user may input the name which identifies a characteristic. The registered characteristics can be selected by the user at the start of gradation adjustment, and the above-described gradation adjustment processing is executed based on the selected characteristics. When making the user selectable, it is also preferable to identify and display only reusable characteristics based on the density value obtained by measuring the patch chart.

Although the number of printers 30 is one in the above-described configuration, there are cases where it is desired to perform printing with the same gradation characteristics with a plurality of printers 30. For example, a case where a plurality of printers 30 of the same model are connected to the communication network 38 and printing is performed under the control of the print server 32 will be described. In that case, the print server 32 sends the common reference image data to each printer 30 to print the patch chart, reads each patch chart with the scanner 34, and grasps the current density characteristics of each printer 30. Then, the reference gradation characteristic generated for the printer having the smallest PDmax among the plurality of printers 30 is set for each printer 30. For example, in the above-described tone-oriented processing, the printer 30 having the smallest PD _C max is selected, and TD _C ′ (x) is determined by (2) using the PD _C max. Is used as a new reference gradation characteristic. The same applies to other colors. In the above-described color balance emphasizing process, PDmax having the highest density reduction rate is selected from the colors of the plurality of printers 30, and new reference tone characteristics are generated for each color based on the selected PDmax. Set to 30.

1 is a block diagram showing a schematic configuration of a gradation adjustment system according to the present invention. It is an outline processing flow figure of gradation adjustment using this system. It is a processing flow diagram of an outline of selection of adjustment contents, and execution. It is a typical graph which shows an example of the new reference | standard gradation characteristic obtained by a fidelity importance process. It is a schematic graph which shows an example of the new reference | standard gradation characteristic obtained by the gradation important process. It is a typical graph showing the relationship between image data and the actual density in a patch chart. 7 is a schematic graph of a gradation correction curve stored in a gradation correction table for each gradation curve shown in FIG. 6. 10 is a schematic graph showing gradation characteristics after calibration when the current maximum density PDmax of the image forming apparatus is lower than the maximum density TDmax of the reference gradation.

Explanation of symbols

  30 Printer, 32 Print server, 34 Scanner, 36 Client computer, 38 Communication network.

Claims (2)

For an image forming apparatus that generates an image composed of a plurality of component colors based on a reference gradation characteristic that defines a correspondence relationship between a color component value of image data and a target density of image formation for the color for each of a plurality of component colors A gradation adjustment system that performs gradation adjustment,
For each of the component colors, reference image input means for inputting reference image data representing a gradation to the image forming apparatus;
Image formation density upper limit detection means for detecting an upper limit value of the density of each component color of the image formed by the image forming apparatus with respect to the reference image data;
Representative color selection means for selecting one representative color from the plurality of component colors based on the upper limit value of the image formation density of each component color of the image forming apparatus;
First gradation characteristic generation means for generating a new reference gradation characteristic of the representative color according to an image formation density upper limit value of the representative color of the image forming apparatus;
Means for generating a new reference gradation characteristic of the component color other than the representative color from the new reference gradation characteristic of the representative color, the new reference gradation characteristic for any of the image data The new reference gradation characteristics of the component colors other than the representative color are generated so that the mutual ratio of the target densities for the component colors is the same as the current relative ratio of the reference gradation characteristics. Second gradation characteristic generating means for
I have a,
The representative color selection means selects the component color corresponding to the minimum value among the ratios of the upper limit value of the image formation density to the maximum density of the current reference gradation characteristic for each component color as the representative color. thing,
Gradation adjustment system characterized by For an image forming apparatus that generates an image composed of a plurality of component colors based on a reference gradation characteristic that defines a correspondence relationship between a color component value of image data and a target density of image formation for the color for each of a plurality of component colors To the computer that controls the gradation adjustment system that performs gradation adjustment,
For each of the component colors, a reference image input procedure for inputting reference image data representing gradations to the image forming apparatus;
An image formation density upper limit detection procedure for detecting an upper limit value of the density of each component color of the image formed by the image forming apparatus with respect to the reference image data;
A representative color selection procedure for selecting one representative color from the plurality of component colors based on the upper limit value of the image formation density of each component color of the image forming apparatus;
A first gradation characteristic generation procedure for generating a new reference gradation characteristic of the representative color according to an image formation density upper limit value of the representative color of the image forming apparatus;
A procedure for generating a new reference gradation characteristic of the component color other than the representative color from a new reference gradation characteristic of the representative color, the new reference gradation characteristic for any of the image data The new reference gradation characteristics of the component colors other than the representative color are generated so that the mutual ratio of the target densities for the component colors is the same as the current relative ratio of the reference gradation characteristics. A second gradation characteristic generation procedure to:
Was executed,
The representative color selection procedure selects, as the representative color, the component color corresponding to the minimum value among the ratios of the image formation density upper limit value to the current maximum density of the reference gradation characteristic for each component color. thing,
Gradation adjustment system control program characterized by

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