JP2000099715A - Picture data processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make more effectively executable the color correction for picture data by using a look-up table. SOLUTION: The colors of read picture data are corrected by a display look-up table 112 and the color-corrected data are displayed on a display. The table 112 regulates the value of output picture data of each of plural regulated points set up in a three-dimensional coordinate system setting up the values of input picture data as coordinate values, the value of output picture data corresponding to the value of optional input picture data is obtained by interpolating operation, the value of output picture data of a regulated point corresponding to the maximum value of the input picture data is set up to a value larger than '255' which is a programmed maximum value and the programmed maximum value is acquired also for an input picture data value smaller than the maximum value, so that a clearer color image of high luminance can be obtained. A look-up table for recording read picture data sets up the value of output picture data corresponding to the minimum value of input picture data to a value smaller than a prescribed minimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data processing apparatus, and more particularly to color correction of image data using a look-up table.

[0002]

2. Description of the Related Art Image data is obtained by, for example, reading of an original image by a scanner, creation by an image creator, reception of image data from a remote device, and the like, printing on a recording medium, CRT display and liquid crystal display. It is output in various forms, such as being displayed on a display such as a display. The look-up table is used for performing image data conversion such as conversion of RGB image data into CMY image data and color correction of image data.
The latter is performed, for example, when image data obtained by reading an original image with a scanner is used as image data representing a color closer to the color of the original image, or when printing the image data on a recording medium, This is performed to print in a color closer to the color of the original image. In this specification, the term “color” is used in a broad sense that includes not only chromatic colors but also achromatic colors.

[0003] If a look-up table is used, for example, input image data that is image data that has not undergone color correction is converted into output image data that is image data that has undergone color correction. If the up table is a table having the values of the output image data for all the values of all the input image data, the capacity of the storage device for storing the lookup table becomes large. Therefore, conventionally, the look-up table has output image data values for only a part of the values of all input image data, and performs interpolation calculation for the other input image data values, thereby obtaining the output image data. Getting data values has been done. This image data processing device
(A) a look-up table that defines the value of the output image data at each of a plurality of defined points set in a coordinate system that uses the value of the input image data as a coordinate value; and (B) a plurality of definitions of the lookup table. And interpolating means for interpolating the value of the output image data corresponding to the value of the input image data based on the value of the output image data at each of the points. If there is a specified point having the same value as the value of the input image data, the value of the output image data at the specified point is directly used as the value of the output image data. If there is no specified point having the same value as the value of the input image data, an interpolation operation is performed based on the value of the output image data at each of the plurality of specified points surrounding the value of the input image data, and The value of the corresponding output image data is determined. With this configuration, the look-up table does not have to be a table having the values of the output image data for all the values of the input image data, and the capacity of the storage device that stores the look-up table can be reduced.

However, the conventional image data processing device provided with a look-up table and interpolation calculation means has the following disadvantages. For example, if the value of the input image data is
If the value of the output image data is a value between the specified point at which the value of the output image data is the highest scheduled value and a value adjacent to the specified point, the output image data corresponding to the value of the input image data Is always smaller than the expected maximum value of the output image data. Therefore, for example, in a CRT color display, among the three primary colors of red, green, and blue, yellow light obtained by mixing red light and green light may not become clear yellow. Further, if the value of the input image data is a value between a specified point at which the value of the output image data is a predetermined minimum value and a value adjacent to the specified point, among the plurality of specified points, The value of the output image data with respect to the data value is always larger than the predetermined minimum value of the output image data. Therefore, for example, if the predetermined minimum value is 0 in a color printer, cyan or magenta is recorded in yellow obtained from yellow among the three primary colors of cyan, magenta, and yellow, and the beauty of recording is improved. Is lost. In the case of a black and white display, beautiful white cannot be obtained.
Black is recorded in white and the appearance becomes poor.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has been made in view of the above circumstances so that a beautiful color can be obtained by an image data processing apparatus having a look-up table and interpolation calculation means. According to the present invention, an image data processing apparatus, a scanner, a display, a printer, a copier, and the like according to the following aspects can be obtained. Each aspect is similar to the claim,
It is divided into sections, each section is numbered, and if necessary, the number of the other section is cited. This is to illustrate the technical features and combinations thereof described in this specification, and it is to be understood that the technical features and combinations thereof described in this specification are limited to the following. Should not be. (1) In an image data processing device including the look-up table of (A) and the interpolation means of (B), the look-up table is output at least at a specified point corresponding to a limit value of input image data. An image data processing device wherein the image data is larger than a predetermined maximum value. The limit value of the input image data is “the highest value of the input image data” when the types of the input image data and the output image data are the same, and is “the lowest value of the input image data” when they are different. The type of image data is luminance data that specifies the intensity of light or density data that specifies the density of a recording material such as ink. In this embodiment, the output image data is luminance data. In the case where the input image data is luminance data, as in the case where the look-up table performs color correction on luminance data and obtains luminance data, for example, The extreme value of the image data becomes the highest value, and when the input image data is the density data, for example, when the look-up table converts the density data into the luminance data, the extreme value of the input image data is obtained. The value is the lowest. Since the value of the output image data at the specified point corresponding to the extreme value of the input image data is set to be larger than the expected maximum value (this is abbreviated as raising the maximum value), the value of the input image data becomes
Even if the value is between a specified point whose coordinate value is the extreme value of the input image data and a specified point adjacent to the specified point, the value of the output image data obtained by the interpolation calculation is the highest expected value. Can exceed. Even if the value of the input image data is not the extreme value, output image data that is equal to or higher than the expected maximum value can be obtained, and for the reason described later, image data that can obtain a beautiful yellow or white image can be obtained. The image data processing apparatus in which the limit value of the input image data is the highest value and the highest value of the output image data has been raised is, for example, a display or a scanner (the read image is scheduled to be reproduced by the display). Image) is output (displayed) by light and provided in a device in which the image data is luminance data. By doing so, the color of the image output by light becomes beautiful. For example, yellow, magenta, cyan, red, green, blue, etc. displayed on a color display become beautiful, and white displayed on a monochrome display becomes beautiful. (2) When the value of the calculated output image data exceeds the predetermined maximum value, the interpolation calculation means includes a restriction means for suppressing the value of the output image data to the predetermined maximum value. The image data processing device according to claim 2. According to this aspect, since the value of the output image data is suppressed to the predetermined maximum value, it is possible to reliably prevent the trouble in the device provided with the image data processing device. For example, when the image data processing device described in (1) is provided in a device that converts multivalued image data into binary image data by an error diffusion method and displays the image data, if the limiting means is not provided, the output image The excess of the maximum value of the data has useless adverse effects on the binarization of the multi-valued image data. However, if the limiting means is provided, this can be avoided.
In the error diffusion method, the difference between the value of the multi-valued image data of a certain pixel and the threshold value is dispersed to pixels other than the pixel, so that the maximum value of the output image data exceeds the predetermined maximum value. If the value is not limited, the difference from the threshold value becomes uselessly larger than the maximum value, and the difference is dispersed to other pixels, which adversely affects the binary image data set for those pixels. But if it is limited to the highest value, it can be avoided.
On the other hand, when the image data processing device described in (1) is provided in a device that converts multivalued image data into binary image data by a dither method and displays the image data, the highest value of the image data is used. Both the object and the one exceeding the maximum value are only converted to values representing the formation of dots, so that the above-mentioned adverse effects do not occur even if no restricting means is provided. However, another problem arises in that, for example, 8 bits are not enough to represent one pixel of the multi-valued image data. Numerical values from 0 to 255 can be represented by 8 bits, whereas, for example, 260 cannot be represented by 8 bits. From this viewpoint, it is desirable to provide a restricting means. (3) The value of the output image data of the plurality of specified points is determined such that the value of the output image data at the specified point corresponding to the limit value of the input image data becomes a predetermined maximum value. The image data processing device according to the above mode (1) or (2), wherein only the value of the output image data at the specified point corresponding to the limit value of the input image data is increased. According to this aspect, the specified point at which the highest value of the output image data is increased is only the specified point corresponding to the limit value of the input image data, and the specified point corresponding to the limit value and the specified point are adjacent to the specified point. Only the output image data between the specified point is affected by the increase of the maximum value. Of the output image data between the defined point corresponding to the extreme value and the defined point adjacent to the defined point, only the output image data close to the defined point corresponding to the extreme value becomes larger than the maximum value. Regardless of the present mode, for example, even if the value of each output image data at the specified point corresponding to the extreme value of the input image data and the specified point adjacent to the specified point is the expected maximum value, the value may be the specified point. The value of the output image data with respect to the input image data, which is a value between them, can be set to the highest scheduled value.
However, in this case, the output image data that is not desirable to be pulled up is also pulled up, and the color output accuracy is reduced. On the other hand, according to the present aspect, the value of the output image data is increased only for the value of the input image data that is extremely close to the limit value, so that the decrease in the output accuracy is avoided. (4) The value of the output image data at the plurality of specified points is determined such that the value of the output image data at the specified point corresponding to the limit value of the input image data becomes a predetermined maximum value. In addition, only the specified point corresponding to the limit value of the input image data and the output image data values of one to five specified points adjacent thereto are increased (1) or (2). Item). For the specified point corresponding to the extreme value of the input image data, the value of the output image data is always larger than the expected maximum value, but for the specified point adjacent to the specified point, the value of the output image data is It may be made larger than a predetermined maximum value, or may be made larger than a predetermined maximum value. If the specified point adjacent to the specified point corresponding to the extreme value of the input image data is increased in a range smaller than the predetermined maximum value, the specified point corresponding to the extreme value of the input image data and the specified point adjacent to the specified point are increased. Not only the output image data between the specified point but also the output image data in a wider area will be affected by the increase in the maximum price, but it is avoided that the degree of the effect changes suddenly. You. The number of specified points at which the value of the output image data is increased is generally selected to be a number sufficiently smaller than the total number of specified points, and generally, the larger the total number of specified points, the larger the selected number. (5) In the image data processing apparatus including the lookup table of (A) and the interpolation means of (B), the lookup table is output at least at a specified point corresponding to a limit value of input image data. An image data processing apparatus wherein the image data is smaller than a predetermined minimum value. The limit value of the input image data is “the minimum value of the input image data” when the types of the input image data and the output image data are the same, and is “the maximum value of the input image data” when they are different. This aspect is an aspect applied when the output image data is density data. For example, as in the case where the look-up table performs color correction on the density data and obtains the density data, If the data is density data, the limit value of the input image data is the lowest value, and the input image data is the luminance data, as in the case where the look-up table converts luminance data into density data. In the case of, the limit value of the input image data becomes the highest value. Since the value of the output image data at the specified point corresponding to the extreme value of the input image data is smaller than the predetermined minimum value (this is abbreviated to the lowering of the minimum value), the value of the input image data is The value of the output image data obtained by the interpolation operation is lower than the planned minimum value even if the value is between the specified point whose coordinate value is the extreme value of the data and the specified point adjacent to the specified point. Can be. Even if the value of the input image data is not the extreme value, it is possible to obtain output image data that is equal to or less than a predetermined minimum value, and it is possible to obtain image data capable of obtaining a beautiful yellow or white image for the reason described later. An image data processing device in which the extreme value of input image data is the lowest value and the lowest value of the output image data has been reduced is, for example, a printer or a scanner (a device in which a read image is scheduled to be reproduced by a printer). ), Etc. are provided in an apparatus in which an image is formed by a recording material such as ink. This makes the color of the image formed by the recording material beautiful. For example, yellow, magenta, cyan, red, green, blue and the like recorded by a color printer become beautiful, and white of an image recorded by a monochrome printer becomes beautiful. (6) When the value of the output image data calculated is lower than the predetermined minimum value, the interpolation calculating means includes a limiting means for raising the value of the output image data to the predetermined minimum value. The image data processing device according to the above aspect (Claim 4). In the present embodiment, the effect similar to that of the embodiment described in the above mode (2) is obtained by raising the value of the output image data to the predetermined minimum value. For example, (5)
If the image data processing device described in the paragraph is provided in a device that converts multivalued image data into binary image data by an error diffusion method and records the image data, the value of the output image data that falls below a predetermined minimum value is multivalued image data. This has the effect of avoiding the useless adverse effect on the binarization of the data, or preventing the problem that 8 bits are not enough to represent one pixel of the multi-valued image data. is there. (7) The value of the output image data at the plurality of specified points is determined such that the value of the output image data at the specified point corresponding to the limit value of the input image data is a predetermined minimum value. The image data processing device according to the mode (5) or (6), wherein only the value of the output image data at the specified point corresponding to the limit value of the input image data is reduced. This embodiment is different from the embodiment described in the above mode (3) in that the value of the output image data at the specified point corresponding to the extreme value of the input image data is reduced. Since the value of the output image data is reduced only for the value of the input image data that is extremely close to the limit value, the effect of avoiding a decrease in output accuracy can be obtained. (8) The value of the output image data at the plurality of specified points is determined such that the value of the output image data at the specified point corresponding to the limit value of the input image data is a predetermined minimum value. Then, only the specified point corresponding to the extreme value of the input image data and the value of the output image data at one to five specified points adjacent thereto are reduced (5) or (6). Item). For the specified point corresponding to the extreme value of the input image data, the value of the output image data is always smaller than the predetermined minimum value, but for the specified point adjacent to the specified point, the value of the output image data is It may be made smaller than the predetermined minimum value, or may be made smaller than the predetermined minimum value. If the specified point adjacent to the specified point corresponding to the extreme value of the input image data is reduced in a range larger than the predetermined minimum value, the specified point corresponding to the extreme value of the input image data and the specified point adjacent to the specified point are reduced. Not only the output image data between the specified point but also the output image data in a wider area will be affected by the minimum price increase, but it is avoided that the degree of the effect changes suddenly. You. The number of specified points at which the value of the output image data is reduced is usually selected to be a number sufficiently smaller than the total number of specified points. Generally, the larger the total number of specified points is, the larger the selected number is. (9) In the image data processing device including the look-up table of (A) and the interpolation calculation means of (B), an output at a specified point corresponding to at least a limit value of input image data is used as the look-up table. A first lookup table in which the image data is larger than a predetermined maximum value; and a second lookup table in which the output image data at least at a specified point corresponding to the extreme value of the input image data is smaller than the predetermined minimum value. An image data processing device provided with a selection means for selecting two lookup tables. The “extreme value of input image data” of the first lookup table and the “extreme value of input image data” of the second lookup table are respectively
The description in the image data processing device described in the paragraphs (1) and (5) applies as it is. The image data processing apparatus of this aspect is provided in an apparatus having both a function of outputting an image using light, such as a display, and a function of outputting an image using a recording material, such as a printer. When the image is output by light, the output image data needs to be luminance data. Therefore, when the first lookup table is selected by the selection unit and the image is output by the recording material, Since the output image data needs to be density data, the selection means selects the second lookup table. As a result, a beautiful yellow or white image can be obtained whether the image is output by light or by the recording material. Further, since the interpolation calculation means is used both when the image is output by light and when the image is output by the recording material, the cost of the apparatus can be reduced accordingly. (10) When the value of the output image data calculated by the interpolation calculating means exceeds the predetermined maximum value, the value of the output image data is suppressed to the predetermined maximum value, and the value of the calculated output image data is The image data processing apparatus according to the above mode (9), further comprising a limiter for raising the value of the output image data to the predetermined minimum value when the value is lower than the predetermined minimum value. According to this aspect, the effects described in the above items (2) and (6) are obtained. (11) The value of the output image data of the plurality of specified points is set such that the first lookup table sets the value of the output image data of the specified point corresponding to the extreme value of the input image data to a predetermined maximum value. After being determined, only the value of the output image data at the specified point corresponding to the extreme value of the input image data is increased, and the second lookup table corresponds to the extreme value of the input image data. After the values of the output image data of the plurality of specified points are determined so that the value of the output image data of the specified point becomes the predetermined minimum value, the output image of the specified point corresponding to the extreme value of the input image data is determined. Only the value of the data has been reduced (9) or (10)
An image data processing device according to claim 1. According to this aspect, it is possible to obtain the operations and effects obtained with respect to the image data processing devices described in (3) and (7). (12) The values of the output image data of the plurality of specified points are set such that the first look-up table sets the output image data of the specified point corresponding to the extreme value of the input image data to a predetermined maximum value. Once defined, a specified point corresponding to the extreme value of the input image data and one or more adjacent points 5
Only the value of the output image data of the specified points or less is increased, and the second lookup table indicates that the value of the output image data of the specified point corresponding to the extreme value of the input image data is a predetermined value. After the values of the output image data at the plurality of specified points are determined so as to be the lowest values, the specified point corresponding to the extreme value of the input image data and one adjacent thereto are defined.
The image data processing apparatus according to the above mode (9) or (10), wherein only the values of the output image data at the specified points of not less than 5 and not more than 5 are reduced. According to this aspect, (4) and (8)
The functions and effects obtained for the image data processing devices described in the above items can be obtained. (13) The interpolation calculation means includes a linear interpolation calculation means for calculating a value of the output image data corresponding to the value of the arbitrary input image data by linear interpolation. Any one of the items (1) to (12) An image data processing device according to claim 1. According to the linear interpolation calculation means, the interpolation calculation can be performed easily and quickly. (14) Including a reading unit that reads an image, and as a processing unit of the image data acquired by the reading unit, (1) through
A scanner including the image data processing device according to any one of (4) and (13). The scanner is a type of image data acquisition device, and may acquire an image in black and white data or may acquire it in color data. If the scanner is provided with the image data processing device described in any one of the above items (1) to (4) and (13), a beautiful image can be displayed on a display without such an image data processing device. Can be displayed. Note that the present invention is also applicable to an image data processing device of an imaging device for a television. (15) Including a reading unit that reads an image, and as a processing unit for image data acquired by the reading unit,
A scanner including the image data processing device according to any one of (8) and (13). (5) to (8), (13)
If the image data processing device described in any one of the above items is provided, it is possible to cause a printer that does not include such an image data processing device to record a beautiful image. (16) A display unit for displaying an image on a screen based on the image data is provided, and any of the items (1) to (4) and (13) is used as a processing unit for the image data supplied to the display unit. A display comprising the image data processing device according to any one of the preceding claims. The display includes, for example, a CRT display,
There is a liquid crystal display and the like. (17) A printing unit that prints an image on a recording medium based on image data is provided, and a processing unit for image data supplied to the printing unit is described in (5) to (8), (1).
A printer comprising the image data processing device according to any one of the above 3). The printer may be a dot printer, and in addition to an ink jet printer and a thermal printer,
A laser printer or the like may be used. (18) a reading unit that reads an image, and a printing unit that prints an image on a recording medium based on image data,
In addition, as a processing section for image data acquired by the reading section and supplied to the printing section, the processing section (5) to (8), (13)
A copy machine comprising the image data processing device according to any one of the above items. (19) A display unit that displays an image on a screen based on image data, and a print unit that prints an image on a recording medium based on the image data, and an image supplied to the display unit and the print unit An image output device comprising the image data processing device according to any one of (9) to (13) as a data processing unit. (20) a reading unit for reading image data, a display unit for displaying an image on a screen based on the image data, and a printing unit for printing an image on a recording medium based on the image data; An image system comprising the image processing device according to any one of (9) to (13) as a processing unit for image data acquired and supplied to the display unit or the print unit.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image data processing apparatus according to an embodiment of the present invention will be described below by taking an image system having a function of reading an image, a function of recording on a recording medium and a function of displaying on a screen as an example. . In FIG. 1, reference numeral 10 denotes a housing, which includes a reading unit 12 for reading image data and a printing unit 16 for printing an image on a recording sheet 14 as a recording medium based on the image data. Reading unit 12
A document feeder 20 for driving a plurality of feed rollers 18 and a drive source for driving the feed rollers 18, a document feeder 22 for feeding a document from which an image is read, and a CCD image sensor 24 for image data reading. . The CCD image sensor 24 includes a lamp device for selectively emitting red light, green light and blue light, and a plurality of CCDs.
, And an optical system for guiding the reflected light from the document to the CCD device. The read original is selectively irradiated with light of three colors, and two-dimensional color read image data is obtained based on the reflected light and the feed of the original.

The printing unit 16 moves a cassette 30 containing the recording paper 14, a recording paper feeder 32 as a recording medium feeder for feeding the recording paper 14, a recording head 34 for recording an image on the recording paper 14, and a recording head 34. And a head moving device 36 for moving. The recording paper feeder 32 includes a plurality of pairs of two feed rollers 38, and the feed rollers 38 are respectively located upstream and downstream in a recording paper feeding direction of a platen 40 provided at right angles to the recording paper feeding direction. Is provided. These feed rollers 38 are driven by a sheet feed motor 42 (FIG.
See).

The recording head 34 is an ink-jet type head for ejecting ink to record an image on the recording paper 14, and includes an ink ejecting head for ejecting cyan ink,
An ink ejecting head ejects magenta ink and an ink ejecting head ejects yellow ink. Each ink jet head has a plurality of ink jet nozzles. Each of the plurality of ink ejecting nozzles has an ejection port and an ink chamber, and ejects ink by applying a driving voltage to a piezoelectric element made of a piezoelectric material constituting a wall of the ink chamber to eject ink.
Record the image in color.

The recording head 34 is mounted on a carriage 46 together with the cartridges 44 containing the four inks. The carriage 46 is moved in a direction perpendicular to the recording paper feed direction by a carriage moving device driven by a carriage drive motor 48 (see FIG. 3), and the recording head 34 is moved along the recording paper 14. The recording paper 14 is fed one by one from the cassette 30 by a paper feed roller 50, and is sent between a platen 40 and a recording head 34 by a recording paper feeding device 32, and an image is recorded by the recording head 34.

A CRT display 58 is provided separately from the reading section 12 and the printing section 16, and a display section 60 is provided.
Is composed. The CRT display 58 is a color display and, as schematically shown in FIG.
It includes electron guns 62, 64, 66 for green and blue, a shadow mask (not shown), and a fluorescent screen 68 on which red, green, and blue phosphors are provided. The electron beams from each of the electron guns 62, 64, 66 stimulate the phosphor of the corresponding color through the shadow mask, so that the image is displayed in color. By changing the intensity of the electron guns 62, 64, 66, various colors can be obtained.

The present image system uses a control device 8 shown in FIG.
0 is provided. The control device 80 is mainly composed of a computer 90 including a PU (processing unit) 82, a ROM 84, a RAM 86 and a bus 88 connecting them. The bus 88 has an input / output interface 9
2, a reading control unit 94 forming the reading unit 12, a recording control unit 96 forming the printing unit 16, a display control unit 98 forming the display unit 60, and the input device 1.
00 and the like are connected. The reading control device 94, the recording control device 96, and the display control device 98 include a control device 80.
The reading control unit 94 controls the original feed motor 20, the CCD image sensor 24, and the like, and the recording control unit 96 operates the paper feed motor 42 and the recording head 34 (more precisely, a plurality of A driving circuit for driving each piezo element of the ink jet nozzle) and the carriage driving motor 48, and a display control device 98.
Controls the electron guns 62, 64, 66. Input device 100
Is constituted by a keyboard provided with, for example, numeric keys, alphabet keys, function keys, etc., and an operator inputs data and the like using the input device 100. The input device may determine whether the operator records image data on the recording sheet 14, displays the image data on the CRT display 58,
When the image data is recorded on the recording sheet 14, the binarization process is used to instruct whether to use an error diffusion pattern or a dither pattern or the like. RO
Various programs including a program for the color correction processing shown in the flowchart of FIG. 4 and the look-up table 1 shown in FIGS.
10, 112, and 114 are stored.

FIG. 5 schematically shows the processing of image data from the reading of image data by the reading unit 12 to the recording of image data by the printing unit 16 and the display of image data by the display unit 60. The read image data obtained by reading the image data in the reading unit 12 is subjected to color correction using the read look-up table 110, and the read image data defines an image of a color that is faithful to the color of the original image. Corrected to data. An image is displayed on the CRT display 58 or recorded on the recording paper 14 based on the image data after the correction.
When the image is displayed on the RT display 58, color correction is performed using the display look-up table 112 so that the image is displayed in a more beautiful color. Using the table 114, the read image data, which is the luminance data, is converted into the recorded image data, which is the density data, and is corrected to data in which an image is recorded in a more beautiful color. Color correction using the look-up tables 110, 112, 114
This is performed in the control device 80. The color correction by the reading lookup table 110 is performed by the display lookup table 112 and the recording lookup table 1.
14, that is, the display look-up table 112 and the recording look-up table 114 can also be used as the reading look-up table 110. Since it is configured so as to be used in combination with the display unit 60 and the print unit 16 of other companies, in order to output standard read image data,
The lookup table 110 for reading is the lookup table 112 for display and the lookup table 1 for recording.
14 is provided separately. When the reading unit 12 is used in combination with the display unit 60 or the printing unit 16 of another company, the reading lookup table 110 is stored in the ROM of the computer constituting the reading control device 96,
The read look-up table 110 is provided to the read control unit 96.
To perform color correction.

The reading section 12 obtains a document by reading it.
The read image data is sent from the reading control unit 96 to the control device.
The read image data is supplied to the
The color correction is performed using the backup table 110.
Reading look-up table that corrects scanned image data
FIG. 6 shows a part of the rule 110. Lookup table for reading
Table 110 stores input image data, that is, read image data.
Points set in a three-dimensional coordinate system that uses the data values as coordinate values
Defines the value of output image data in each of. Read image
The image data is color image data and is three primary colors of light.
Each of red, green, and blue (hereinafter represented by R, G, and B, respectively)
Input, because it contains luminance data representing the intensity of
The coordinate system that uses the image data values as coordinate values is three-dimensional
It is. In this embodiment, each of the three primary colors
256 levels of gradation are set, and 3
The maximum value of each of the planned axes, that is, the R, G, and B axes is 25
5 and the lowest planned value is 0. And the prescribed point
Is, in principle, 17 points (including 0) for every 16 gradations for each axis.
) Is set for each of the three-dimensional coordinate systems. ^Three 
Number of specified points are set, and each specified point is
To define the position of the specified point in the three-dimensional coordinate system.
Coordinate values, that is, the values of the input image data and their specified points
The output image data value is associated with the output image data.

An output image data value corresponding to an arbitrary input image data value is obtained by an interpolation operation. As described above, if 17 defined points are set for each of the three axes, a three-dimensional coordinate system in which the values of the input image data are coordinate values is, in principle, 16 on one side and 8 It divided the prescribed points 16 ³ cubes whose vertices. The interpolation operation is performed based on the values of the output image data at the eight specified points that define the cube, in which cube the value of the arbitrary input image data is located. Output image data corresponding to the data value is obtained.

As shown in FIG. 9, each side of the cube set in the coordinate system using the value of the input image data as a coordinate value is parallel to the axis of the coordinate system. In general, a hexahedron having a vertex based on the value of image data is a distorted hexahedron in which each side is not parallel to a coordinate axis. A point corresponding to a point whose coordinate value is the value of the input image data is located in the distorted hexahedron. actually,
Although each side of the hexahedron is not a straight line, it is approximated to a straight line, and the output image data is obtained by a linear interpolation operation based on the coordinate values of eight defined points defining the distorted hexahedron. The technique of this linear interpolation calculation is well known, and the description is omitted. FIG. 6 shows a case where input image data (250, 250,
The coordinate values of _eight specified points D _{1 to} D ₈ that define a cube including the point P specified by 0) and the values of output image data at each of the specified points are shown. In order to obtain output image data corresponding to the input image data (250, 250, 0), as a result of performing a linear interpolation operation based on the output image data at each of the eight specified points, the output image data (252, 250) , 0) is obtained.

When output image data values are obtained for all input image data values, color correction for display or recording is performed on the data. Whether the read image data should be recorded on the recording paper 14 or displayed on the CRT display 58 is instructed from the input device 100 by the operator. First, a case where an image is displayed on the CRT display 58 will be described. in this case,
Since the image is displayed by mixing the three colors of light of R, G, and B, the image data supplied to the display unit 60 may be luminance data, but the display look-up table 112 is used to obtain a clearer color image. Is used to correct the image data.

This color correction is performed according to the color correction processing shown in FIG. First, in step 1 (hereinafter abbreviated as S1; the same applies to other steps), input image data for one pixel is read. This input image data is output image data previously obtained by color correction using the lookup table 110 for reading. Next, S2 is executed to determine whether or not image data is recorded on the recording paper 14. Here, since the display of the image data on the CRT display 58 has been instructed by the operator, the determination result in S2 is NO and S
3 is executed, the coordinate values of eight specified points that define the cube including the point specified by the input image data are obtained, and the values of the output image data at each of the specified points are displayed in the display look-up table 112. Taken from.

The display look-up table 112 is, similarly to the reading look-up table 110, set to a three-dimensional coordinate system that uses input image data values as coordinate values.
^This defines the value of the output image data at each of the ^three specified points. The predetermined maximum value of each of the three axes is 255 and the minimum value is 0, but the maximum value of the output image data is the maximum value of the predetermined value. 255. The display look-up table 112 is a look-up table in which both input image data and output image data are luminance data, and performs color correction of the luminance data to luminance data, and corresponds to the maximum value which is the limit value of the input image data. That is, the value of the output image data at the specified point is set to be larger than the predetermined maximum value. FIG. 7 shows a part of the display look-up table 112. In FIG. 7, in the three-dimensional coordinate system,
Eight defined points D _{1 to} D ₈ defining a cube including a point P defined by the input image data (250, 250, 0)
And the coordinate values of the output image data at each of the specified points.

Next, step S4 is executed to obtain the value of the output image data corresponding to the value of the input image data.
Linear interpolation is performed based on the values of the output image data at the specified points D _{1 to} D ₈ . In a three-dimensional coordinate value whose coordinate value is the value of input image data, a point defined by arbitrary input image data is included in a cube having eight specified points as vertices. In a three-dimensional coordinate system in which coordinate values are used, the coordinates are in a distorted hexahedron defined by eight specified points. Although each side of the hexahedron is not a straight line, it is approximated to a straight line, and the output image data is obtained by a linear interpolation operation based on the coordinate values of eight specified points defining the distorted hexahedron.

After the interpolation calculation, step S5 is executed to determine whether or not image data is to be recorded on the recording paper 14, but the result of this determination is NO and step S6 is executed. S
In 6, each of the three values for R, G, and B constituting the output image data is a predetermined maximum value, that is, 2 values.
A determination is made whether it is greater than 55. As described above, the maximum value of the output image data is the expected maximum value of 25.
5, and the value of the output image data may be larger than a predetermined maximum value. Input image data (250,
If the result of the linear interpolation operation performed on (250, 0) is (257, 256, 0), then R and G
Is larger than 255, the result of the determination in S6 is YES, and S7 is executed, and the value is suppressed to 255, which is the expected maximum value. Since B is 255 or less, the determination result in S6 is NO, and S7 is not executed. The value of the output image data thus obtained is S
8 is supplied to the display control device 98.

As described above, even if the value of the input image data is smaller than the maximum value, the output image data having the expected maximum value can be obtained.
The output image data for (0,0) is (255,255,
0). In the display section 60, the magnitude of the driving voltage for driving the electron guns 62, 64, 66 is set based on the value of the output image data. In the CRT display 58, yellow is obtained by a mixture of red light and green light, and beautiful yellow is obtained by setting each of the red and green values to a predetermined maximum value.

A case where an image is recorded on the recording paper 14 will be described. In this case, after execution of S1, S2 is executed, but the result of the determination is YES, and S9 is executed. The coordinate values are obtained, and the values of the output image data at the specified points are fetched from the recording look-up table 114 shown in FIG. Since the recording of the image on the recording paper 14 is performed using ink, density data that defines the density of the ink is required.

The three primary colors of light, R, G, and B, and the three primary colors of ink, cyan, magenta, and yellow (hereinafter, C,
M and Y) are complementary colors as shown in FIG. Therefore, the simplest is 2 which is the highest gradation value.
By subtracting the value of the luminance data from 55, the density data is obtained. This calculation is performed by the lookup table 1 for recording.
14. Lookup table for recording 1
Reference numeral 14 denotes a three-dimensional coordinate system in which values of input image data are coordinate values, that is, R, G, and B are each axis, and the maximum value of each axis is 2
55 is a table in which the values of output image data are specified for each of a plurality of specified points set in a three-dimensional coordinate system whose lowest value is 0. The specified point is, in principle, 3
It is set by 17 points for every 16 gray scale every 3 axes dimensions coordinate system 17 ^three specified points are set in the entire 3-dimensional coordinate system.

Since density data is obtained for the luminance data, the value of the output image data is a value in a three-dimensional coordinate system having C, M, and Y as three axes, and represents the density. This 3
The maximum value of each axis of the dimensional coordinate system is 255, and the planned minimum value is 0.
However, since the density data is obtained by subtracting the value of the luminance data from the maximum value 255 of the gradation value, the lowest value of the output image data corresponds to the highest value of the input image data. In the lookup table 114, the value of the output image data at the specified point corresponding to the maximum value which is the limit value of the input image data is set to be smaller than the predetermined minimum value 0 as shown in FIG. . FIG. 8 shows coordinate values of _eight specified points D _{1 to} D ₈ that define a cube including a point P defined by input image data (250, 250, 0) in the lookup table 114 for recording. The coordinate values of the output image data at each of these specified points are illustrated.

After execution of step S9, step S4 is executed, a linear interpolation operation is performed based on the data read in step S9, and the value of the output image data with respect to the value of the input image data is obtained. Next, S5 is executed to determine whether or not to print an image on the recording paper 14, but the determination result is YES, and in S10, whether or not the value of the output image data is smaller than 0 is determined. Will be For example, if the value of the input image data is (250, 250, 0), the result of the linear interpolation operation is (-1, -1, 255), and the determination result of S10 for C and M is YES. Then, S11 is executed, and the value of the output image data is raised to a predetermined minimum value and set to 0. For Y, the determination result in S10 is NO, and S11 is not executed. The output image data values (0, 0, 25
5) is supplied to the recording control device 96 in S12.

As described above, the recording look-up table 1
14, the value of the output image data corresponding to the highest value of the input image data is made smaller than the planned minimum value, and the value below the planned minimum value is raised to the planned minimum value and set to 0, If the coordinate values of the input image data are (250,
250, 0), even if the data is not data that completely defines yellow, printing is performed only with yellow ink, and a beautiful image in which cyan and magenta are not mixed in yellow can be obtained. Using the recording look-up table 114, the conversion of the luminance data into the density data is performed, and the color correction is performed.

The image data corrected as described above is multi-valued image data. When displaying an image on the CRT display 58 on the display unit 62, the electron guns 62 and 64 are based on the multi-valued image data. , 66 are set, but when an image is recorded on the recording paper 14, binary image data, that is, dot formation data for instructing to form a dot for each pixel or instructing not to form a dot. Is converted to dot non-formation data.
This data conversion is performed according to an error diffusion pattern of the error diffusion method or a dither pattern of the dither method. In this embodiment, the operator instructs which pattern is used for binarization. For example, if the original image from which the image data has been read by the reading unit 12 is a photograph, it is binarized according to the error diffusion method, and if the original image is a text-only document, it is binarized according to the dither method.

In the recording control device 96, if output image data obtained by color conversion using the recording look-up table 114 is supplied, the binarization process shown in FIG. 11 is performed. This processing is stored in the ROM of the computer constituting the recording control device 96. First, S1
In 01, it is determined whether or not the image data is binarized by the error diffusion method. If the binarization of the image data by the error diffusion method is instructed, the determination result of S101 is Y
When the ES becomes ES, S102 is executed, and the image data is binarized according to the error diffusion pattern.

In the above description, in order to facilitate understanding, the recording look-up table 114 simply converts luminance data into density data, and performs color conversion on data near the highest value among input image data. Although described as a table in which correction is performed, in practice, when multi-valued image data is converted into binary image data according to an error diffusion pattern, color correction that can obtain a color more faithful to the original image is also performed. It is configured as follows. The recording look-up table 114 also serves as an error diffusion-compatible look-up table. Therefore, when the value of the output image data corresponding to the value of the input image data is obtained by the linear interpolation operation using the recording look-up table 114, the reading lookup table 110 and the display lookup table 112 are used. As in the case where the value of the output image data is subjected to the linear interpolation operation, the value of the output image data is obtained in the distorted hexahedron.

The error diffusion pattern is configured, for example, as shown in FIG. Processing of image data using an error diffusion pattern is already well known and will be briefly described. In FIG. 12, the asterisks (*) indicate pixels for which the multi-valued image data is converted into the binary image data, and the value of the multi-valued image data obtained for the pixel is a threshold, for example, the maximum value and the minimum value of the recording density. Is compared to the intermediate value
Error is diffused while binary image data is created. If the value of the multi-valued image data is equal to or greater than the threshold value, dot formation data is created, and the value obtained by subtracting the maximum value of the recording density from the value of the multi-valued image data is the error set in the error diffusion pattern. It is distributed to neighboring pixels according to the diffusion value. The value obtained by multiplying 1/48 of the error by each value in FIG. 12 is added to the value of the multi-valued image data of the corresponding pixel. If the value of the multi-valued image data is smaller than the threshold value, dot non-formation data is created, and a value obtained by subtracting the minimum value of the recording density from the value of the multi-valued image data is set in the error diffusion pattern. Is distributed to neighboring pixels according to the calculated numerical value. Here, the image is a color image, and the process using the error diffusion pattern is performed using a common error diffusion pattern for each of the multi-valued image data defining the densities of C, M, and Y.

If processing by the dither method is instructed,
When the result of the determination in S101 is NO, S103 is executed, and the multilevel image data is binarized according to the dither pattern. As shown in FIG. 13, the dither pattern is formed in a matrix, and a plurality of threshold values forming the matrix are compared with the value of the multi-valued image data to create binary image data.

The dither pattern is created at the time of designing the image data processing apparatus of the image system, and has a color of an error diffusion method image which is an image realized by an error diffusion correspondence lookup table and image data processed by the error diffusion pattern. , And a color of a dither image which is an image realized by the image data processed by the error diffusion correspondence lookup table and the dither pattern dither pattern. When the luminance data is converted into the density data using the recording look-up table 114, the color correction corresponding to the error diffusion pattern is performed. Therefore, the image data processed by the dither pattern is also processed by the error diffusion correspondence lookup table. Color correction is being performed. The image is a color image, and when the image data is processed by the dither pattern, the processing is performed according to the dither pattern for the values of the respective colors C, M, and Y.

The creation of a dither pattern will be described. When creating a dither pattern, first, a look-up table 114 for recording that also serves as an error diffusion-compatible lookup table as an error diffusion-compatible data correction rule is created.
This step is an error diffusion corresponding lookup table creation step as an example of the error diffusion corresponding data correction rule preparation step. As described above, when converting the luminance data into the density data, the recording look-up table 114 sets the lowest value of the output image data corresponding to the highest value of the input image data to a value smaller than the predetermined lowest value of 0. And the color of the image recorded by the image data processed by the error diffusion pattern is made to be a regular color, for example, a color faithful to the color of the original image. Next, an error diffusion image which is an image realized by the image data processed by the recording look-up table 114 and the error diffusion pattern, and a dither image which is an image realized by image data processed by the dither pattern of the dither method. Compare with

In this comparison, a plurality of types of input image data (multi-value luminance data) for obtaining a dot gain curve are prepared, and the first dot, which is a dot gain curve of an error diffusion image, is generated for each input image data. This is performed by acquiring a gain curve and a second dot gain curve, which is a dot gain curve of a dither image, and comparing the two. This operation is performed using a computer.

The input image data for acquiring the dot gain curve forms dots in a dot forming area including a larger number of pixels than the number of error diffusion values constituting the error diffusion pattern and the number of thresholds constituting the dither pattern. And set the same value for each pixel. This value is selected from the minimum value to the maximum value of the luminance gradation, and a plurality of types of input image data for acquiring dot gain curves having this value, that is, different gradation levels are prepared. Note that the number and density of dots formed in the dot formation area according to the dot gain curve acquisition input image data are the same even if the color of the ink is different, and the first dot gain curve and the second dot gain curve ,
It is sufficient to acquire any one of the colors M and Y.
Therefore, the input image data for dot gain curve acquisition, which is luminance data, is created so that any one of C, M, and Y colors can be obtained, and the density differs for a plurality of types.

When acquiring the first dot gain curve, first, the input image data for acquiring the dot gain curve is converted into density data using the lookup table 110 for recording, and is processed by an error diffusion pattern. Obtain value image data. If the binary image data is obtained, it is possible to determine at which pixel a dot is to be formed without actually recording an image on the recording paper 14, and for each of a plurality of types of dot gain curve acquisition input image data A dot formation area is calculated for each of the plurality of obtained error diffusion method images. The dot formation area is preferably smaller than the dot formation area, and it is desirable to calculate the dots formed in the area where the error is equalized. In the present embodiment, the ink does not permeate the recording paper 14 so that the edges are not blurred, and even if some of the dots formed in adjacent pixels may overlap each other, the It is assumed that the concentration does not increase.

The relationship between the number of dots (dot formation area) and the density within a unit area is known in advance, and the first dot gain curve representing the relationship between the number of the plurality of types of dots and the density calculated as described above. Can be obtained. FIG. 15 shows the first dot gain curve. The number of dots corresponds to the value (level) of the dot gain curve acquisition input image data, and the curve shown in FIG. 15 is a curve showing the relationship between the level of the dot gain curve acquisition input image data and the density. It can be said that there is. The step of obtaining the first dot gain curve in this way is the first dot gain curve obtaining step.

When obtaining the second dot gain curve, a dither pattern illustrated in FIG. 13B is used. This dither pattern is based on the dither pattern shown in FIG. 13A and is a combination of four dither patterns, and is a normal dither pattern which is a basic dither pattern. Although the dither pattern shown in FIG. 13B is an 8 × 8 matrix for easy understanding, the print unit 16 of the present embodiment converts the image into two.
Recording is performed at 56 gradations.
An 8 × 128 matrix dither pattern is used.

The input image data for obtaining the dot gain curve, which is the luminance data, is stored in the lookup table 114 for recording.
Is converted into density data by using
Is converted into binary image data in accordance with the dither pattern shown in (1) to obtain the number of dots and calculate the dot formation area. In this case, it is desirable to set a dot number acquisition area that is at least an integral multiple of the area occupied by the pixels forming the dither pattern in the dot formation area, and acquire the dot number and the dot formation area. Based on the relationship between the dot formation area and the density that is known in advance,
A second dot gain curve (see FIG. 15) representing the relationship between the number of dots and the density within a unit area is obtained. The step of obtaining the second dot gain curve in this way is the second dot gain curve obtaining step.

Next, by comparing the first dot gain curve with the second dot gain curve, the densities of the dither method image and the error diffusion method image are compared for a plurality of types of dot numbers. Thus, the step of comparing the first dot gain curve and the second dot gain curve is a dot gain curve comparison step, and constitutes an image comparison step together with the first dot gain curve acquisition step and the second dot gain curve acquisition step. ing. Since the dither method image and the error diffusion method image have the same number of dots but different dot arrangements and overlapping dot occurrence rates, the densities of the two images generally do not match. The density of the dither image is often smaller than that of the error diffusion image. Therefore, a dither pattern changing step is performed to substantially match the color of the error diffusion image with the color of the dither image.

This change is performed by changing the threshold value forming the dither pattern illustrated in FIG. 13B to the threshold value forming the dither pattern illustrated in FIG. 13C. The normal dither pattern shown in FIG. 13B is corrected for color correction, and the dither pattern shown in FIG. 13C is obtained. The dither pattern shown in FIG. 13C is a special dither pattern. In the present embodiment, creating a dither pattern is to create this special dither pattern. In the normal dither pattern shown in FIG. 13B, since the density of the dither method image is lower than the density of the error diffusion method image, the normal dither pattern may be changed so that the density of the dither method image increases. It is only necessary to reduce a part of the threshold value forming the normal dither pattern so that the dot formation data can be easily created.

As is apparent from the graph of FIG. 15, when the number of dots (the value (level) of the input image data for dot gain curve acquisition) is between the maximum and the minimum, the number of dots is smaller than that between the maximum and the minimum. Large difference in density. for that reason,
As shown in FIG. 14, among a plurality of thresholds forming a normal dither pattern, a plurality of intermediate thresholds are
The amount of change is made larger than other threshold values. Thereby,
The amount of increase in the number of dot formation data is greater for input image data at an intermediate level than for input image data at other levels, and the density difference can be reduced. FIG.
In FIG. 13B, four basic patterns forming the normal dither pattern shown in FIG.
, The threshold values constituting the normal dither pattern, the threshold values in each of the basic patterns I to IV, and the sum of the change amounts are shown in a table.

In this embodiment, the threshold value of the normal dither pattern is changed by changing the maximum value (pixel value) of the maximum value of the difference between the color density of the error diffusion image and the color density of the dither image. The ratio is determined to be 3% or less. By changing the normal dither pattern in this way, there is no difference between the color of the error diffusion method image and the color of the dither method image that can be recognized by a human, and there is no sense of incongruity. As described above, the process of changing the normal dither pattern is the dither pattern changing process. The comparison between the first and second dot gain curves is automatically performed by a computer. Normally, the change of the dither pattern is performed by a computer in accordance with a preset change program, and the image obtained by the process based on the dither pattern obtained by the computer change and the process based on the error diffusion pattern. This is performed by comparing the obtained image with the operator, and instructing a change using an input device with respect to a threshold value with an insufficient change amount and an excessive threshold value. Usually, the change of the dither pattern is performed by a computer in principle, so that the amount of work of the operator is small.

As is apparent from the above description, in the present embodiment, the display look-up table 112 is the first look-up table, and constitutes the look-up table according to claim 1; The up-table 114 is a second look-up table, which constitutes the look-up table according to claim 3, wherein the part of the control device 80 that executes S4 constitutes an interpolation operation means.
6 and S7 constitute a limiting means for suppressing the value of the output image data to a predetermined maximum value, and S10 and S11 execute a limiting means for increasing the value of the output image data to a predetermined minimum value. And the part executing S2 constitutes the selection means. Further, the recording control device 9
The part that executes S102 and S103 of No. 6 constitutes a binarization unit.

The printing unit 1 of the image system described above
6. Look-up table 114 for recording of control device 80
A printer having an image data processing apparatus according to an embodiment of the present invention can be obtained by performing color conversion and color correction of image data by using. In addition, a display provided with the image data processing device according to an embodiment of the present invention is provided by a portion that performs color correction of image data using the display unit 60 of the image system and the display look-up table 112 of the control device 80. can get. Further, a portion for performing color correction and color conversion of image data by using the reading unit 12, the printing unit 16, and the reading look-up table 110 and the recording look-up table 114 of the control device 80 of the above-described image system provides the present invention. A copy machine including the image data processing device according to one embodiment is obtained. In addition, a portion for performing color correction and color conversion of image data by using the print unit 16, the display unit 60, the display look-up table 112 and the record look-up table 114 of the control device 80 of the above-described image system provides the present invention. An image output device including the image data processing device according to one embodiment is obtained.

The display control device 98 may include a display look-up table 112 to perform color correction for displaying image data, and the recording control device 96 may include a recording look-up table 114 and perform image correction. Color may be corrected for recording. Further, the reading control device 94 includes a reading lookup table 110,
Color correction of the read image data may be performed. In this case, the display unit 60 constitutes a display including the image data processing device according to an embodiment of the present invention, and the printing unit 16 constitutes a printer including the image data processing device according to an embodiment of the present invention. , The reading unit 12 and the printing unit 16 constitute a copier provided with an image data processing device according to an embodiment of the present invention, and the printing unit 16 and the display unit 60 include an image data processing device according to an embodiment of the present invention. The image output device provided with the above is constituted.

In the above embodiment, the printer unit 1
In No. 6, the color image is recorded by using three colors of ink of cyan, magenta, and yellow. However, a color image may be recorded by further using black ink. In this case, the multi-valued image data for setting the luminance for each of R, G, and B is converted to multi-valued image data for setting the respective densities of C, M, Y, and K using a look-up table.

Further, the printer is not limited to a color printer, but may be a black and white printer. Further, the printer may be a dot printer other than the ink jet printer, for example, a thermal printer.

In each of the above-described embodiments, the control units 94, 96, and 98 are provided for each of the reading unit 12, the printing unit 16, and the display unit 60, and the control unit 80 for performing color correction is provided. However, reading control, recording control, display control, and color correction control may be performed by a single control device.

Further, in each of the above embodiments, after the read image data is corrected using the reading look-up table 110, the read image data is corrected using the display look-up table 112 or the recording look-up table 114. However, the correction using the lookup table 110 for reading may be omitted, or the lookup table for display may also serve as the lookup table for reading, and the lookup table for recording may be used as the lookup table for recording. They may be combined. When the display lookup table also serves as the reading lookup table, the lookup table may be provided in the reading unit or may be provided in the display unit.

In each of the above embodiments, the recording look-up table 114 has three functions, that is, it converts luminance data into density data, and converts the image data into an image having a normal color realized by the error diffusion method. It had been provided with a function of performing color correction on image data to be a color and performing color correction by making the value of output image data at a specified point corresponding to the highest value of input image data smaller than a predetermined lowest value. , May be performed by another look-up table. However, if both the lookup table performing the functions and the lookup table performing the function are defined point lookup tables that define the output image data of the defined points, and the interpolation calculation is performed, the function of the lookup table is performed. It is desirable that the functions of and be performed after. Further, when the image data is subjected to color correction for recording, instead of making the value of the output image data at the specified point corresponding to the highest value of the input image data smaller than the predetermined lowest value, the lowest value of the input image data is used. The color correction may be performed by making the value of the output image data at the specified point corresponding to the predetermined value smaller than the predetermined minimum value. This function is denoted by '. The above functions, and the function of 'may be performed by separate look-up tables, respectively, two functions may be performed by one look-up table, and the remaining one function may be performed by another look-up table.
One look-up table may be used. However, the lookup table for the function 'is provided separately from the lookup table for the function, and
Used after the lookup table for the function.
Further, when the three functions are not performed by one look-up table, and these look-up tables are defined point look-up tables that define output image data of defined points, and interpolation is performed, It is desirable that the function of 'is performed last. Also,
If the function is performed by one look-up table and is performed before the function, the look-up table for the function is a table that converts density data into density data. If performed after the function, the look-up table for the function is a table that obtains luminance data by performing color correction on the luminance data. It should be noted that the look-up table that performs the function after the above function is used only when the image data is processed by the error diffusion method, and may not be used when the image data is processed by the dither method. .

Further, by adding the above function to the reading look-up table, a scanner having an image data processing apparatus according to an embodiment of the present invention can be obtained. A scanner is provided with a reading lookup table to which a document reading mechanism and a function are added, and performing color correction using the lookup table.

Further, in the reading lookup table,
By adding a function of performing color correction by making the value of output image data at a specified point corresponding to the maximum value of input image data larger than a predetermined maximum value, an image data processing apparatus according to another embodiment of the present invention can be provided. A scanner equipped with the above is obtained.

In addition, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a front view (a partial cross section) schematically showing an image system including an image data processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a CRT display constituting a display unit of the image system.

FIG. 3 is a block diagram conceptually showing a configuration of a control device for controlling color correction of image data in the image system.

FIG. 4 is a ROM of a computer constituting the control device.
5 is a flowchart showing a color correction process stored in the storage device.

FIG. 5 is a block diagram functionally showing a flow of processing of image data by the control device.

FIG. 6 is a table showing a part of a read look-up table stored in a ROM of the computer.

FIG. 7 is a table showing a part of a display look-up table stored in a ROM of the computer.

FIG. 8 is a table showing a part of a recording look-up table stored in a ROM of the computer.

FIG. 9 is a diagram illustrating a linear interpolation calculation performed in the color correction processing.

FIG. 10 is a diagram illustrating conversion of luminance data to density data performed in the color correction processing.

FIG. 11 is a flowchart showing a binarization process stored in a ROM of a computer constituting a recording control device provided in the printing unit.

FIG. 12 is a diagram showing an error diffusion pattern for processing image data by an error diffusion method in the binarization processing.

FIG. 13 is a diagram showing a dither pattern for processing image data by a dither method in the binarization processing.

FIG. 14 is a diagram illustrating a change of the dither pattern.

FIG. 15 is a graph showing a first dot gain curve of an error diffusion image and a second dot gain curve of a dither image.

[Description of Signs] 12: reading unit 16: printing unit 60: display unit
80: control device 96: recording control device 98: display control device 11
0: Lookup table for reading 112: Lookup table for display 114: Lookup table for recording

Claims (4)

[Claims] 1. A look-up table for defining a value of output image data at each of a plurality of specified points set in a coordinate system using a value of input image data as a coordinate value, and a plurality of specified points of the look-up table Based on the value of the output image data in each of the values of the output image data corresponding to the value of any input image data interpolation operation means and an interpolation operation means, the lookup table, at least An image data processing apparatus, wherein output image data at a specified point corresponding to an extreme value of input image data is larger than a predetermined maximum value. 2. The image processing apparatus according to claim 1, wherein the interpolation calculating means includes a limiting means for suppressing a value of the output image data to a predetermined maximum value when a value of the calculated output image data exceeds the predetermined maximum value. The image data processing device according to claim 1, wherein: 3. A look-up table for defining a value of output image data at each of a plurality of specified points set in a coordinate system using a value of input image data as a coordinate value, and a plurality of specified points of the look-up table Based on the value of the output image data in each of the values of the output image data corresponding to the value of any input image data interpolation operation means and an interpolation operation means, the lookup table, at least An image data processing apparatus, wherein output image data at a specified point corresponding to an extreme value of input image data is smaller than a predetermined minimum value. 4. The interpolation calculating means includes limiting means for raising the value of the output image data to the predetermined minimum value when the value of the calculated output image data is lower than the predetermined minimum value. The image data processing device according to claim 3, wherein: