JPH1016304A - Image-outputting apparatus, image-processing apparatus, method for outputting and processing image, and method for correcting density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a density of output images proper by correcting a change of an output density characteristic due to a change in output conditions for the images. SOLUTION: A density correction image is formed by an image signal of a predetermined density level. A density of the image is measured by a density- measuring part 131. A density to be measured and a standard density at a corresponding level are compared at a density correction table-forming part 120, thereby to form a density correction table 119 determining a rule to correct a density level of image data so that an output density characteristic shows a linearity. A density-correcting part 118 corrects the density of image data according to the density correction table 119.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output apparatus, an image processing apparatus, a method therefor, and a density correction method, and more particularly to an image output apparatus having a density correction function, an image processing apparatus, a method therefor, and an image. The present invention relates to a density correction method for an output device.

[0002]

2. Description of the Related Art In a printer, as one method of forming a gray scale image such as a gray scale, the number of dots to be drawn is controlled in accordance with the density level of an image signal by using a pseudo halftone expression such as a dither method. There is a known technique. In such a printer, the number of drawing dots determined according to the density level is set in advance by measuring the density of the output image under general conditions and according to the measurement result.

[0003]

However, in the printer according to the conventional example described above, for example, the environment such as the temperature and humidity at the time of printing, the temperature change and deterioration of the photosensitive drum and the fixing device of the printer, the remaining amount of toner, and the like. Depending on the factors, the density of the output image may be higher or lower than the expected density. Such a problem becomes remarkable especially in an image of an intermediate density level.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to correct fluctuations in output density characteristics due to fluctuations in image output conditions and optimize the density of an output image.

[0005]

An image output apparatus according to the present invention is an image output apparatus having a density correction function, comprising: a density measuring means for measuring the density of an output image; and an output measured by the density measuring means. Correction rule setting means for comparing the density of the image with the standard density and setting a correction rule for correcting the density level of the image signal so that the density of the output image is appropriate; and an image signal according to the set correction rule. And an image forming unit that forms an output image based on the corrected image signal.

In the image output apparatus of the present invention, the density measuring means measures the density of an output image corresponding to image signals having a plurality of different density levels, and the correction rule setting means uses the density measuring means. It is preferable that each of the plurality of measured densities is compared with a standard density at a corresponding density level, and a correction rule for all the density levels is set based on the plurality of comparison results.

In the image output apparatus of the present invention, it is preferable that the correction rule setting means sets a correction rule such that the relationship between the density level of the image signal before correction and the density of the output image becomes linear.

In the image output apparatus according to the present invention, the correction rule setting means generates a table in which the relationship between the density level of the image signal before correction and the density level of the image signal after correction has a one-to-one correspondence. It is preferable to set a correction rule for correcting the density level of the image signal using the table.

Preferably, the image output apparatus of the present invention further comprises a density correction image forming means for forming an output image for measuring the density by the density measuring means.

An image output method according to the present invention is an image output method for outputting an image by correcting the density, wherein a density measuring step of measuring the density of the output image, and a density of the output image measured in the density measuring step. And a standard density, and a correction rule setting step of setting a correction rule for correcting the density level of the image signal so that the density of the output image is appropriate,
The method includes a correction step of correcting a density level of an image signal according to a set correction rule, and an image forming step of forming an output image based on the corrected image signal.

A density correction method according to the present invention is a method for correcting the density of an output image in an image output device, comprising: a density measurement step for measuring the density of the output image; A correction rule setting step of comparing the density with the density and setting a correction rule for correcting the density level of the image signal so that the density of the output image becomes appropriate.

An image processing apparatus according to the present invention comprises: means for inputting a density value obtained by reading a reference image output by a predetermined image forming apparatus; and a density value and a standard density value input by the input means. Calculating means for calculating the difference value of
Creation means for creating a density correction table based on the difference value; correction means for performing density correction of input image data based on the density correction table; and image data corrected by the correction means to the image forming apparatus. Output means for outputting.

It is preferable that the image processing apparatus of the present invention further includes a communication unit capable of performing bidirectional communication with the image forming apparatus.

In the image processing apparatus according to the present invention, the reference image is composed of patches having a smaller number of gradations than the number of gradations that can be formed by the image forming apparatus.
It is preferable to perform an interpolation operation based on the difference value.

An image processing method according to the present invention comprises the steps of: inputting a density value obtained by reading a reference image output by a predetermined image forming apparatus; An operation step of calculating a difference value of
A creation step of creating a density correction table based on the difference value, a correction step of performing density correction of input image data based on the density correction table, and the image data corrected by the correction step to the image forming apparatus. And an output step of outputting.

According to a second image processing apparatus of the present invention, input means for inputting image data respectively corresponding to a plurality of objects constituting one image, and a reference image output by a predetermined image forming apparatus are read. Correction means for performing density correction of the image data for each object by a density correction characteristic based on the obtained data.

A second image processing apparatus according to the present invention further comprises a developing means for developing the image data of the object into raster data for each pixel, and the correcting means performs processing on the raster data developed by the developing means. It is preferable to perform density correction by using the following method.

In the second image processing apparatus of the present invention, it is preferable that the developing means outputs raster data of a color formed by the image forming apparatus.

In the second image processing apparatus according to the present invention, it is preferable that the raster data is yellow, magenta, cyan, and black data.

According to a second image processing method of the present invention, an input step of inputting image data corresponding to a plurality of objects constituting one image, and a reference image output by a predetermined image forming apparatus are read. And correcting the density of the image data for each object using a density correction characteristic based on the obtained data.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a printer according to an embodiment of the present invention. The host computer 150 includes color information, character information, graphic information, a raster image,
Image data (including PDL data) including control information and the like is generated and transmitted to the printer 100.

The printer 100 includes a host computer 1
An image processing unit 110 that receives image data from the image processing unit 50 and converts (decompresses) the image data into drawing data (raster image data), and a printer that forms an output image based on the drawing data supplied from the image processing unit 110 Engine 13
0.

The image processing unit 110 receives image data from the host computer 150 via the interface (I / F) 111 and stores the image data in the reception buffer 112 in order. The object generation unit 204 controls the reception buffer 112
Color information, text information,
Print information such as graphic information and raster images is converted to intermediate information (hereinafter referred to as
(Also referred to as an object) and sequentially stores them in the object buffer 114. At this time, if the print information is gray level data such as gray level settings, color level settings, and multi-valued raster images, the density correction unit 118 corrects the density levels.

The rendering unit 115 draws an image in the band buffer 117 based on the object stored in the object buffer 114, and generates raster image data. At this time, the dither processing unit 116 performs pseudo halftone processing on the image drawn in the band buffer 117. The raster image data generated in the band buffer 117 is sent to the printer engine 130 as drawing data. The printer engine 130 forms an output image in pseudo-halftone expression on an output medium (recording paper or the like) by, for example, an electrophotographic process.

Here, the correction of the density level by the density correction unit 118 is not limited to when the object is generated by the object generation unit 113, but when drawing in the band buffer 117, that is, the image data of each object is converted into raster image data. Alternatively, it may be executed after being developed.

The printer engine 130 includes the density measuring unit 1
31. When creating a density correction table 119 that defines a rule for correcting the density of an output image, the density measuring unit 131 uses a density correction image (reference data) formed based on drawing data (reference data) having a predetermined density level. The density of the image is measured, and the measurement result is notified to the density correction table creating unit 120. The printer engine 130 is
It is connected to the image processing unit 110 via a transmission path capable of bidirectional communication.

The density correction table creating section 120 compares the notified measurement result with the standard density at the density level of the drawing data corresponding to the density correction image related to the measurement, and performs density correction based on the result. A density conversion table 119 that defines a density conversion rule that makes the relationship between the density level of the image data before density correction by the unit 118 and the density of the output image linear is created.

FIG. 2 is a block diagram showing an example in which a part of the printer 100 is constituted by software. Components having the same functions as those of the printer 100 shown in FIG. 1 are denoted by the same reference numerals. In the printer 100 shown in FIG. 2, the object generation unit 113, the density table generation unit 120, and the density correction unit 118 are realized by an object generation program 113 ', a density correction table generation program 120', and a density correction program 118 ', respectively. The control program 211 receives the image data,
This is a program that controls the printing process that generates drawing data based on the image data and supplies the drawing data to the printer engine 130.

The RAM 220 has areas used as the reception buffer 112, the object buffer 114, and the density correction table 119. The CPU 201 has a ROM 2
It operates based on each program stored in the printer 10 and controls the operation of the printer 100. Hereinafter, the operation of the printer according to the present embodiment will be described with reference to the printer 100 shown in FIG.

FIG. 3 is a flowchart showing the flow of a printing process controlled based on the control program 211.

In step S301, image data is received from the host computer 150 via the interface 111, and is sequentially stored in the reception buffer 112. In step S302, image data (for example, a drawing command) for one processing unit is read from the reception buffer 112.

In step S303, it is determined whether or not the processing for all pages has been completed. If the processing has not been completed, the flow advances to step S304. In step S304, it is determined whether the processing for one page has been completed. If the processing has not been completed, the process proceeds to step S305. If the processing has been completed, the process proceeds to step S309 to render the page. The drawing data is sent to 130.

In step S305, it is determined whether or not the image data to be processed is a drawing command including color information or gradation data such as a color raster image. If the gradation data is gradation data, the process proceeds to step S306. If not, the process proceeds to step S308.

In step S306, the density control program 118 'is started to correct the density level of the image data. This correction is performed according to the density correction table 119. On the other hand, in step S308, it is determined whether or not the image data is mask data such as character information and graphic information. If the image data is mask data, the process proceeds to step S307; otherwise, the process proceeds to step S311. In step S307, the object generation program 113 'is started, an object is generated based on the image data whose density level has been corrected, and stored in the object buffer 114. Then, the process returns to step S302 to process the subsequent image data.

As described above, by performing the density correction processing for each object, efficient density conversion becomes possible in relation to other image processing. For example, other image processing such as conversion from RGB data to YMCK data, masking, and UCR processing (for example, also performed in step S306) is performed for each object, and the object after one processing is performed. By sequentially providing subsequent processing, efficient use of memory resources and high-speed image processing can be realized. Therefore, it is preferable to execute the density correction processing for each object in accordance with another image processing mode.

If it is determined in step S308 that the image data is not mask data, step S3
In step 11, after performing image processing according to the type of image data, the process returns to step S302.

The above processing (steps S305 to S305)
308 and S311), and if it is determined in step S303 that the processing for one page has been completed, the process proceeds to step S309.

In step S309, the objects held in the object buffer 114 are sequentially supplied to the rendering unit 115. The rendering unit 115 generates a raster image on the band buffer 117 while performing dither processing by the dither processing unit 116. Step S
At 310, the raster image generated on the band buffer 117 is sent to the printer engine 130 as drawing data. The printer engine 130 forms an output image on an output medium based on the drawing data.

The above procedure can be changed as appropriate.
For example, the density correction processing (step S306) may be performed on raster image data output from the rendering unit 115. Also, for example, the rendering process (step S309) ends one page (step S30).
Instead of waiting for "Yes" in step 4, the program may be executed at any time (that is, for each object) after the object generation processing (step S307).

Next, the flow of the process of creating the density correction table 119 will be described. FIG. 4 is a flowchart showing the flow of the density correction table creation processing controlled based on the density correction table creation program 120 '. In a color printer, this processing is performed for each of the separated colors (YMC
K). However, only one color will be described below for convenience of description.

In this embodiment, the setting range of the density level is 0 (minimum density level) to 255 (maximum density level). Note that this setting range can be appropriately changed according to the embodiment.

The density correction table creation processing is performed, for example, at the time of power-on, after outputting 100 images, at preset timings such as one hour intervals, or based on the temperature, the temperature of the printer engine 130, etc. Executed when it fluctuates beyond the value.

In this embodiment, the setting range of the density level 0 to 255 is divided into four, and the area of the density levels 0 to 63 (level 1) is divided into the level area 1 and the density levels 64 to 12
7 (level 2) is defined as level area 2 and density level 12
An area of 8 to 191 (level 3) is defined as a level area 3, and an area of density levels 192 to 255 (maximum density level) is defined as a level area 4.

A density correction table creation program 120 '
Prints the density correction images corresponding to the density levels of level 1 to level 3 and the maximum density level by the printer engine 130.
And the density of the correction image is determined by the density measuring unit 131.
And a density correction table 119 based on the relationship between the measurement result corresponding to each level and its standard density.
Create (update)

In the present embodiment, the density level 63
The density (measured value) of the density correction image corresponding to (level 1), 127 (level 2), and 191 (level 3) is changed to the density (measurement) of the density correction image corresponding to the density level 255 (maximum density level). Value). Then, the standard densities corresponding to the density levels 0, 63, 127, 191 and 255 are set to 0, 0.25, 0.5, 0.75 and 1, respectively.
The standard density is compared with the normalized density (measured value), and a density correction table 119 is created based on the result.

Hereinafter, a specific processing flow will be described. First, in step S401, as described above, levels 1 to
A density correction image corresponding to the level 3 and the maximum density level is formed in the printer engine 130. In step S402, the density of the density correction image is measured by the density measurement unit 130, and the density of the density correction image corresponding to level 1 to level 3 is normalized by the density of the maximum density correction image.

In step S403, it is checked whether or not the output density at level 1 fluctuates by comparing the normalized density of the level 1 density correction image with the standard density 0.25. As a result, when there is a change in the output density, the process proceeds to step S404, and when there is no change (or when the output density is minute), the process proceeds to step S406.

In the step S404, the contents of the level area 1 of the density correction table 119 are updated, and in the step S40
In 5, the content of the level area 2 of the density correction table 119 is updated, and the process proceeds to step S406.

In step S406, it is checked whether or not the output density at level 2 fluctuates by comparing the normalized density of the level 2 density correction image with the standard density 0.5. As a result, when there is a change in the output density, the process proceeds to step S407, and when there is no change (or when the output density is minute), the process proceeds to step S410.

In step S407, the contents of the level area 2 of the density correction table 119 are updated (step S40).
5) It is determined whether or not the update has been performed. If the update has been performed, the process proceeds directly to step S409. On the other hand, if the update has not been performed, the process proceeds to step S408 to update the contents of the level area 2 of the density correction table 119. Proceed to S409. In step S409, the contents of the level area 3 of the density correction table 119 are updated.

In step S410, it is checked whether or not the output density at level 3 fluctuates by comparing the normalized density of the level 3 density correction image with the standard density 0.75. As a result, when there is a change in the output density, the process proceeds to step S411, and when there is no change (or when it is very small), a series of processes is ended.

In step S411, the contents of the level area 3 of the density correction table 119 are updated (step S40).
9) It is determined whether or not the update has been performed. If the update has been completed, the process proceeds directly to step S413. On the other hand, if the update has not been performed, the process proceeds to step S412 to update the contents of the level area 3 of the density correction table 119. It proceeds to S413. In step S412, the contents of the level area 4 of the density correction table 119 are updated.

FIG. 5 is a diagram showing the relationship between the density level of image data and the output density (output density characteristic) in an ideal state. As shown in FIG. 5, in an ideal state, the characteristic curve 500 is a straight line, and the output density characteristic has linearity. The printer 100 is in a normal state,
This characteristic is maintained, but due to fluctuations in temperature and humidity, temperature fluctuations and deterioration of the photosensitive drum and the fixing device in the printer engine 130, changes in the remaining amount of toner, and the like, that is, fluctuations in output conditions. Characteristics fluctuate.

FIG. 6 is a diagram showing an example of a change in output density characteristics due to a change in output conditions. A characteristic curve 501 shows an output density characteristic when the normalized output density is 0.2 at level 1, 0.4 at level 2, and 0.7 at level 3. The above-described density correction table creation processing is performed using the characteristic curve 5
A density correction table for correcting the density level of the image data so that 01 matches the ideal characteristic curve 500 is created.

FIG. 7 is a diagram showing an example of the density correction table. In the figure, the left column shows the density correction program 1
Image data before correction by 18 '(original image data)
Concentration level. The right column of the figure shows the correction values created (updated) by the density correction table creation processing. For example, if the density level of the original image data is 64 with reference to the density correction table 119, the density correction program 118 'converts the density level to 77 and transfers it to the object generation program 113'.

A specific example of a process (corresponding to step S405 or S408) for updating the contents of the level area 2 (density levels 64-127) of the density correction table 119 will be described below.

Here, as shown in FIG.
It is assumed that the output density at (density level 63) is 0.2 and the output density at level 2 (density level 127) is 0.4.

In this case, the standard density of level 1 is set at 0.
The difference 1 between 25 and the output density 0.2 is 0.25-0.2
= 0.05. The difference 2 between the standard density 0.5 and the output density 0.4 at level 2 is 0.5-0.4
= 0.1.

The level 1 correction value for correcting the characteristic indicated by the characteristic curve 501 in accordance with the density correction table 119 and matching the characteristic curve 500, which is an ideal output density characteristic, is expressed by ((difference 1) + (level 1 Standard density)) × (maximum density level) = (0.05 + 0.25) × 255 = 76.5.

The correction value for level 2 is ((difference 2) + (standard density of level 2)) × (maximum density level) = (0.1 + 0.5) × 255 = 153. 77 and 153 obtained by rounding these are written in the density correction table 119 as correction values at the density levels 63 and 127, respectively. Also, the density level 64
The correction values of to 126 are calculated as values on a straight line connecting the correction value of the density level 1 and the correction value of the density level 2, and are written in the density correction table 119.

Note that correction values can be calculated for other level areas in the same manner.

As described above, an image for density correction is formed,
By measuring the output density by the density measuring unit 131 and updating the density correction table, it is possible to maintain ideal density characteristics irrespective of fluctuations in output conditions.

In the above description, the density correction table is updated on the basis of the output densities at the three density levels. In the present invention, the number of density levels used as a reference when updating the density correction table is determined. Without limitation, any number of concentration levels may be referenced. in this case,
By creating a reference image having a smaller number of tones than the number of tones that can be formed by the printer engine 130, labor can be saved. Further, the correction method is not limited to the linear interpolation as described above, and higher-order interpolation may be performed.

In the above description, the output density characteristic is corrected by forming an image for density correction. In the present invention, for example, the density of the output image in a normal printing process is measured, and the density is measured. The present invention is also applicable to a case where the output density characteristic is corrected by comparing the density with the standard density corresponding to the density level of the image data constituting the area to be measured.

The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), and can be applied to a single device (for example, a copier, Facsimile machine, etc.). Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and a computer (or CPU or MPU) of the system or apparatus to store the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the program.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0071]

According to the present invention, there is an effect that the fluctuation of the output density characteristic due to the fluctuation of the output condition of the image can be corrected and the density of the output image can be optimized.

[0072]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a printer according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example in which a part of the configuration of the printer is configured by software.

FIG. 3 is a flowchart illustrating a flow of a printing process based on a control program.

FIG. 4 is a flowchart illustrating a flow of a density correction table creation process executed based on a density correction table creation program.

FIG. 5 is a diagram illustrating a relationship (density characteristic) between an image data density level and an output density in an ideal state;

FIG. 6 is a diagram illustrating an example of a change in density characteristics due to a change in output conditions.

FIG. 7 is a diagram illustrating an example of a density correction table.

Claims (29)

[Claims] 1. An image output apparatus having a density correction function, comprising: a density measuring means for measuring the density of an output image; and comparing the density of the output image measured by the density measuring means with a standard density. Correction rule setting means for setting a correction rule for correcting the density level of the image signal so that the density of the image is appropriate; correction means for correcting the density level of the image signal according to the set correction rule; And an image forming means for forming an output image based on the image signal. 2. The density measuring means measures the density of an output image corresponding to image signals of a plurality of different density levels, respectively, and the correction rule setting means calculates a density of the plurality of densities measured by the density measuring means. 2. The image output device according to claim 1, wherein each of the image output devices is compared with a standard density at a corresponding density level, and a correction rule is set at all density levels based on a plurality of comparison results. 3. The correction rule setting means sets a correction rule such that the relationship between the density level of an image signal before correction and the density of an output image becomes linear.
Alternatively, the image output device according to claim 2. 4. The correction rule setting means generates a table in which the relationship between the density level of the image signal before correction and the density level of the image signal after correction is in a one-to-one correspondence. 4. The image output apparatus according to claim 1, wherein a correction rule for correcting the density level of the image is set. 5. The image forming apparatus according to claim 1, further comprising a density correcting image forming unit that forms an output image for measuring a density by the density measuring unit. Image output device. 6. An image output method for correcting a density and outputting an image, comprising: a density measuring step of measuring the density of the output image; and comparing the density of the output image measured in the density measuring step with a standard density. A correction rule setting step of setting a correction rule for correcting the density level of the image signal so that the density of the output image is appropriate; and a correction step of correcting the density level of the image signal according to the set correction rule. And an image forming step of forming an output image based on the corrected image signal. 7. The density measuring step measures the densities of output images corresponding to image signals of a plurality of different density levels, respectively, and the correction rule setting step includes the step of calculating a plurality of densities of the plurality of densities measured in the density measuring step. 7. The image output method according to claim 6, wherein each image is compared with a standard density at a corresponding density level, and correction rules for all density levels are set based on a plurality of comparison results. 8. The correction rule setting step sets a correction rule such that the relationship between the density level of the image signal before correction and the density of the output image becomes linear.
Alternatively, the image output method according to claim 7. 9. The correction rule setting step generates a table in which the relationship between the density level of the image signal before correction and the density level of the image signal after correction is in a one-to-one correspondence, and the table is used to generate the image signal. 9. The image output method according to claim 6, wherein a correction rule for correcting the density level is set. 10. A density correction image forming step of forming an output image for measuring a density in the density measuring step.
The image output method according to any one of the above. 11. A density correction method for an output image in an image output device, comprising: a density measurement step of measuring the density of the output image; and comparing the density of the output image measured in the density measurement step with a standard density. A correction rule setting step of setting a correction rule for correcting the density level of the image signal so that the density of the output image is appropriate. 12. The density measuring step measures the densities of output images corresponding to image signals of a plurality of different density levels, respectively, and the correction rule setting step includes the step of calculating a plurality of densities of the plurality of densities measured in the density measuring step. 12. The density correction method according to claim 11, wherein each density is compared with a standard density at a corresponding density level, and a correction rule for all density levels is set based on a plurality of comparison results. 13. The correction rule setting step, wherein the correction rule is set such that the relationship between the density level of the image signal before correction and the density of the output image becomes linear. 13. The density correction method according to item 12. 14. The correction rule setting step generates a table in which the relationship between the density level of the image signal before correction and the density level of the image signal after correction is in a one-to-one correspondence, and the table is used to generate the image signal. 14. The density correction method according to claim 11, wherein a correction rule for correcting the density level is set. 15. The image forming apparatus according to claim 11, further comprising a density correcting image forming step of forming an output image for measuring density in the density measuring step. Density correction method. 16. A means for inputting a density value obtained by reading a reference image output by a predetermined image forming apparatus, and calculating a difference value between the density value input by the input means and a standard density value. Calculation means, creation means for creating a density correction table based on the difference value, correction means for performing density correction of input image data based on the density correction table, and image data corrected by the correction means. An output unit for outputting to an image forming apparatus. 17. The image forming apparatus according to claim 16, further comprising a communication unit capable of two-way communication with the image forming apparatus.
An image processing apparatus according to claim 1. 18. The image processing apparatus according to claim 18, wherein the reference image is composed of patches having a smaller number of tones than the number of tones that can be formed by the image forming apparatus, and the creating unit performs an interpolation operation based on the difference value. The image processing apparatus according to claim 16, wherein: 19. A step of inputting a density value obtained by reading a reference image output by a predetermined image forming apparatus, and calculating a difference value between the density value input in the input step and a standard density value. A calculating step, a creating step of creating a density correction table based on the difference value, a correcting step of performing density correction of input image data based on the density correction table, and the image data corrected by the correcting step. An image processing method, comprising: outputting an image to an image forming apparatus. 20. The image processing method according to claim 19, further comprising a communication control step of controlling bidirectional communication with the image forming apparatus. 21. The method according to claim 21, wherein the reference image is composed of patches having a smaller number of tones than the number of tones that can be formed by the image forming apparatus, and the creating step performs an interpolation operation based on the difference value. 20. The image processing method according to claim 19, wherein: 22. An input unit for inputting image data respectively corresponding to a plurality of objects constituting one image, and a density correction characteristic based on data obtained by reading a reference image output by a predetermined image forming apparatus. An image processing apparatus comprising: a correction unit configured to perform density correction of image data for each object. 23. An image processing apparatus, further comprising: a developing unit for developing the image data for each object into raster data for each pixel.
23. The image processing apparatus according to claim 22, wherein the correction unit performs density correction on the raster data expanded by the expansion unit. 24. The image processing apparatus according to claim 23, wherein said developing means outputs raster data of a color formed by said image forming apparatus. 25. The image processing apparatus according to claim 24, wherein the raster data is yellow, magenta, cyan, and black data. 26. An input step of inputting image data corresponding to a plurality of objects constituting one image, and a density correction characteristic based on data obtained by reading a reference image output by a predetermined image forming apparatus. A correction step of performing density correction of the image data for each object. 27. The image processing apparatus further comprises a developing step of developing the image data of each object into raster data of each pixel,
27. The image processing method according to claim 26, wherein in the correction step, density correction is performed on raster data expanded in the expansion step. 28. The image processing method according to claim 27, wherein the developing step outputs raster data of a color formed by the image forming apparatus. 29. The image processing method according to claim 28, wherein the raster data is yellow, magenta, cyan, and black data.