JP2002051225A - Device and method for processing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately correct the change of picture quality with the conversion of gradation. SOLUTION: When the correction of a gradation conversion condition is instructed (YES in 156 and 160), after the gradation conversion condition is corrected (162), a color correction condition corresponding to the corrected gradation conversion condition is operated so that the saturation and hue for each pixel of image data, to which color correction is applied, converted according to the corrected gradation conversion condition can become almost uniform with the saturation and hue for each pixel of image data, to which the same image data are converted according to a standard gradation conversion condition, and color correction is performed on the color correction condition corresponding to this conversion condition (lightness is almost uniform and the hue is almost uniform in terms of the ratio of the difference between each value of RGB and that of the pixel of gray). To the image data, the gradation conversion is performed on the corrected gradation conversion condition and the color correction is performed on the operated color correction condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus and method, and more particularly to an image processing method for converting the gradation of image data and an image processing apparatus to which the image processing method is applied.

[0002]

2. Description of the Related Art A preferable color reproduction characteristic when reproducing a subject photographed by a camera as an image on a recording medium is different depending on the kind of the subject and the use of the image. As a material,
Many types of photographic materials having different characteristics have been developed and manufactured. For example, shooting by a professional photographer (especially shooting in a photo studio or shooting for portrait creation)
In the case where a photographic print is created from an image recorded on a photographic film by the above photographing, a photographic film or a photographic paper having a soft characteristic in which color skipping and color collapse hardly occur in an area corresponding to a human face in the image. Is used. On the other hand, brilliant photographic prints are preferred for general photographs and amateurs, and photographic films and photographic papers with high contrast characteristics are often used.

[0003] The photographer selects a photographic film in accordance with, for example, the photographer's own preference and the type of the subject to be photographed, and performs photographing. For example, if the client is a professional photographer, the type of subject and the purpose of the image, such as creating a photographic print using photographic paper developed for professional use (for example, photographic paper with soft characteristics) The photographic light-sensitive material is properly used according to the situation.

However, in order to properly use the photographic materials according to the type of the subject and the purpose of the image as described above, it is necessary to prepare a large number of photographic materials having different characteristics in advance. In addition to the burden on the user, the task of properly using the photographic light-sensitive material itself is complicated.

For this reason, image data obtained by reading an image recorded on a photographic film by a photoelectric conversion element is converted according to a gradation conversion characteristic determined according to the type of the subject, the purpose of the image, and the like, and the gradation is converted. By recording an image on a photographic material using the converted image data, it is conceivable to create a photographic print of a finish suitable for the type of subject, image use, etc. from a single or a small number of photographic materials. Can be However, when the gradation of image data is converted, at the same time, unintended changes in image quality (especially, changes in saturation)
There was a problem that would occur.

As a technique related to the above, Japanese Patent Laid-Open No. 5-3 is disclosed.
Japanese Patent No. 28132 discloses that in a digital image forming apparatus such as a digital printer or a digital copying machine, when a user inputs a target gradation curve by using an input unit, a light emission control unit outputs the exposure data based on the inputted gradation curve. The image is adjusted so that the color tone (saturation, etc.) of the output image does not change even if the gradation curve changes, by performing the correction and performing the color masking correction by the color masking correction means in accordance with the input of the gradation curve. A forming apparatus is disclosed.

[0007]

However, the technique described in the above publication realizes color masking correction by performing a matrix operation, and controls the gradation hard and soft and the saturation up / down control. For example, when a gradation curve that increases the saturation is selected, a change in the saturation is selected by selecting a masking coefficient that decreases the saturation as a masking coefficient (matrix coefficient) used for color masking correction. The saturation change amount is adjusted by adjusting the value of the non-diagonal element of the masking coefficient.

For this reason, especially when a gradation curve whose inclination is not constant from the highlight to the shadow is selected, a change in image quality such as saturation is changed over the entire range from the highlight to the shadow. It is difficult to correct with high accuracy over a wide range, and there is a problem that the accuracy of correction for a change in image quality caused by converting the gradation of an image is low.

The present invention has been made in view of the above-mentioned facts, and has as its object to provide an image processing apparatus and an image processing method capable of accurately correcting a change in image quality due to gradation conversion.

[0010]

According to another aspect of the present invention, there is provided an image processing apparatus, comprising: a conversion unit for converting image data; and a conversion characteristic of gradation conversion for the image data. Means for controlling the conversion characteristics of the conversion means so that the gradation of the image data is converted according to the conversion characteristics specified via the specification means, and an image according to the specified conversion characteristics. The image data that has been converted by the conversion means is re-converted so that the change in the ratio of the difference of each color component to the gray of each pixel of the image data due to the conversion of the gradation of the data is corrected. Or control means for controlling the conversion characteristics of the conversion means.

According to the first aspect of the present invention, when the conversion characteristic of the gradation conversion for the image data is specified via the specifying unit, the control unit converts the gradation of the image data according to the specified conversion characteristic. Thus, the conversion characteristics of the conversion means for converting the image data are controlled. Further, the control means is configured to correct the change in the ratio of the difference of each color component from gray of each pixel of the image data due to the conversion of the gradation of the image data according to the designated conversion characteristic. Or re-converts the image data that has been converted by the conversion, or controls the conversion characteristics of the conversion means.

Thus, the ratio of the difference of each color component to the gray of each pixel of the image data whose gradation has been converted according to the designated conversion characteristic is the same or substantially the same as the image data before the gradation conversion. Then, the image data is corrected by re-conversion of the image data or control of the conversion characteristics. If the ratio of the difference of each color component with respect to gray is the same or substantially equal, the saturation or hue of each pixel is the same or substantially the same even if the brightness is different, so the image data is corrected as described above. This makes it possible to accurately correct a change in image quality due to gradation conversion over the entire region from highlight to shadow.

As the image data according to the first aspect of the present invention, for example, as described in the second aspect, a photographic film is irradiated with light and transmitted through an area on the photographic film where an image is recorded. Image data obtained by converting light into an electric signal by a photoelectric conversion sensor can be applied. In place of the above, for example, image data obtained by imaging with a digital still camera or digital video camera, image data generated by a computer, or the like may be applied.

According to the first aspect of the present invention, the re-conversion of the image data by the control means or the control of the conversion characteristic of the conversion means may be performed by the conversion characteristic specified by the control means. The color component value of each pixel of the image data when the image data whose gradation has been converted according to
2 ′, G2 ′, B2 ′, and the color component values of each pixel of the image data obtained by converting the image data without gradation conversion are R2, G
2, B2, R2 '-(R2' + G2 '+ B2') / 3 ≒ R2- (R2 + G
2 + B2) / 3 G2 '-(R2' + G2 '+ B2') / 3 @ G2- (R2 + G
2 + B2) / 3 B2 '-(R2' + G2 '+ B2') / 3 @ G2- (R2 + G
2 + B2) / 3.

In the above equation, (R2 '+ G2' + B2 ')
/ 3 represents each color component value of a pixel whose brightness is substantially the same as that of a pixel whose color component value is R2 ′, G2 ′, B2 ′ and whose hue is gray, and (R2 + G2 + B2) / 3 indicates that each color component value is R2, G
2 and B2 represent the respective color component values of the pixel whose brightness is substantially the same and whose hue is gray. By performing re-conversion of the image data in accordance with the conversion characteristics satisfying the above equation, or controlling the conversion characteristics of the conversion unit, the saturation and hue of each pixel of the image data whose gradation has been converted can be determined by each pixel. Irrespective of the brightness, the saturation or the hue of each pixel of the image data before the gradation conversion can be made the same or substantially the same.

The correction of the change in the ratio of the difference of each color component to the gray of each pixel of the image data can be realized by converting the image data using, for example, a multidimensional lookup table. For example, when the control means is configured to include a multi-dimensional lookup table, as described in claim 4, the control means controls the conversion of the gradation of the image data by the conversion means. The conversion data set so that the change in the ratio of the difference of each color component with respect to the gray of each pixel is corrected is set in a multidimensional lookup table, and the conversion means is set by the multidimensional lookup table in which the conversion data is set. Can be configured to reconvert the image data that has undergone the conversion according to.

When the conversion means is configured to convert the image data using a multidimensional lookup table, for example, the control means includes:
A conversion characteristic designated through the designation means, and a conversion characteristic for correcting a change in a ratio of a difference of each color component to gray of each pixel of the image data when the gradation of the image data is converted according to the conversion characteristic. Is set in a multi-dimensional lookup table with the conversion data of the conversion characteristic in which the conversion characteristics are superimposed, the conversion characteristic of the conversion means can be controlled.

When the conversion means is configured to convert the image data by the multi-dimensional look-up table, for example, the control means controls the image data input to the multi-dimensional look-up table. By setting the conversion data of the conversion characteristic for converting only the data corresponding to the achromatic portion according to the conversion characteristic specified through the specifying unit in the multi-dimensional lookup table, the conversion characteristic of the conversion unit May be configured to be controlled. In this case, among the image data input to the multi-dimensional lookup table, the data corresponding to the chromatic portion does not change in saturation or hue. Therefore, it is necessary to suppress a change in image quality due to gradation conversion. Can be.

Also, various methods can be considered as a method of designating the conversion characteristic of the gradation conversion for the image data. For example, as described in claim 7, in the invention according to claim 1, the conversion is performed via the designating means. The slope of the characteristic may be specified. In this case, it is difficult for the operator to specify a complicated conversion characteristic via the specifying means, but it is possible to easily specify a simple conversion characteristic.

For example, as described in claim 8, the conversion characteristic is independently specified in units of each range when the range from highlight to shadow is divided into a plurality of ranges via the specifying means. It may be. in this case,
It becomes possible for an operator to set desired conversion characteristics with high accuracy.

Further, for example, as described in claim 9,
A first storage unit for storing a plurality of types of conversion characteristics is provided, and a specific conversion characteristic is selected from a plurality of types of conversion characteristics stored in the first storage unit via a designating unit, so that image data is stored. May be specified. In this case, it is possible to set a desired conversion characteristic in advance and store it in the first storage means. Even when the desired conversion characteristic is a complicated characteristic, it is easy to specify the conversion characteristic. It can be carried out.

Further, for example, as set forth in claim 10, a second storage means for storing the conversion characteristic specified via the specifying means is provided, and a correction to the conversion characteristic stored in the second storage means is designated. The conversion characteristic of the gradation conversion for the image data may be specified by the instruction via the means. In this case, it is also possible to recall the conversion characteristics previously specified by the operator via the specifying means and stored (saved) in the second storage means via the specifying means for reuse.

In the image processing method according to the present invention, when the conversion characteristic of the gradation conversion for the image data is designated via the designation means, the gradation of the image data is designated via the designation means. Control the conversion characteristics of the conversion to the image data so that the image data is converted according to the specified conversion characteristics, and the grayscale of each pixel of the image data is accompanied by the conversion of the gradation of the image data according to the specified conversion characteristics. Re-convert the image data that has undergone the conversion, so that the change in the ratio of the difference for each color component is corrected,
Alternatively, since the conversion characteristics of the conversion with respect to the image data are controlled, a change in image quality due to gradation conversion can be corrected with high accuracy, as in the first aspect of the present invention.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an image processing system 10 according to the present embodiment. The image processing system 10 according to the present embodiment includes a film scanner 12, a media driver 14, and an image data receiving device 16 as input devices for inputting image data, and displays an image as an output device for outputting an image. CRT 20, a laser printer 22 for exposing and recording an image on photographic paper, a CD-R for writing image data to a CD-R
A writing device 24 is provided.

The film scanner 12 irradiates a photographic film such as a negative film or a reversal film with light, and a film image on the photographic film (a negative image or a positive image visualized by photographing a subject and developing the film). Is read by a reading sensor (which may be a line sensor or an area sensor) such as a CCD and outputs image data obtained by reading. The film scanner 12 is, for example, 1
35 size photographic film, 110 size photographic film, and photographic film (24
0 size photographic film: so-called APS film), 12
Film images of photographic films of size 0 and size 220 (Brownie size) can be read.

The media driver 14 includes a magnetic disk such as a floppy (registered trademark) disk (FD), an optical disk such as a CD-R, and a magneto-optical disk (M
O), P that can be loaded into a digital still camera (DSC)
Any one of various information storage media such as a C card, a smart media, and an IC card (hereinafter, these are collectively referred to as “digital camera card”) is set, and image data stored in the set information storage medium is read out. Output.

The image data receiving device 16 is connected to a computer network such as the Internet, and receives and receives RGB image data from an information processing device (for example, a personal computer (PC)) via the computer network. Output image data.
The film scanner 12, the media driver 14, and the image data receiving device 16 are connected to the image data pre-processing unit 26 of the image processing device 18, and the image data output from these image data input devices is transmitted to the image data pre-processing unit 2.
6 is input.

The image data pre-processing unit 26 performs predetermined different pre-processing on the input image data depending on the image data input source. The pre-processing for the image data input from the film scanner 12 includes, for example, dark correction, density conversion, shading correction, defective pixel correction, and the like. The pre-processing for the image data input from the media driver 14 includes, for example, decompression of the image data compressed and recorded on the information storage medium, and image processing such as improvement in sharpness. The pre-processing for the image data input from the image data receiving device 16 includes, for example, decompression of the compressed image data (for example, JPEG format image data) received by the image data receiving device 16.

The image data input from the film scanner 12, the media driver 14, and the image data receiving device 16 includes an image output format (laser printer 22).
Output format designation information for designating whether to expose and record an image on a recording material or to write image data on a CD-R by the CD-R writing device 24. This output format designation information is input to various devices described below in a state attached to the image data.

The film scanner 12 according to the present embodiment performs two readings at different resolutions on each film image recorded on a photographic film. In the first reading at a relatively low resolution (hereinafter, referred to as pre-scan), even when the density of the film image is extremely low (for example, a negative image of an underexposure in a negative film), saturation of accumulated charge by the reading sensor is performed. The reading is performed under the reading conditions determined so as not to cause the inconvenience.

A pre-scan memory 28 and a fine scan memory 30 are connected to the image data pre-processing unit 26, and a first image processing unit 32 and a setup operation unit 34 are connected to the pre-scan memory 28, The second image processing unit 36 is connected to the memory 30. When the low-resolution image data is input from the film scanner 12 by performing the pre-scan, the image data pre-processing unit 26 performs pre-processing on the low-resolution image data and outputs the pre-process to the pre-scan memory 28. I do.

The image data pre-processing unit 26 performs a pre-scan memory 28 and a fine scan memory 30 for the image data input from the media driver 14 and the image data input from the image data receiving device 16.
The image data output to the pre-scan memory 28 is converted into low-resolution image data equivalent to the low-resolution image data obtained by the pre-scan, and then output to the pre-scan memory 28. The low-resolution image data output to the prescan memory 28 is input to the setup operation unit 34 via the prescan memory 28.

The setup operation section 34 and the first image processing section 32 have a CPU, a ROM, a RAM, and an input / output port connected to each other via a bus, and have a storage such as a hard disk drive (HDD) in the input / output port. It can be realized by a single microcomputer having a configuration in which the devices are connected. By causing the microcomputer to execute a predetermined program, the microcomputer functions as a first image processing unit 32 and a setup calculation unit 34. Can be done.

The setup calculation unit 34 converts the low-resolution image data input via the pre-scan memory 28 into
If the image data is obtained by performing pre-scanning with the film scanner 12, an image feature amount such as density is calculated based on the low-resolution image data. Film scanner 1
2 determines reading conditions for performing re-reading at a relatively high resolution (hereinafter, referred to as fine scan), and outputs the determined reading conditions to the film scanner 12.

The set-up operation section 34 outputs the same image output from the image data preprocessing section 26 to the second image processing section 36 via the fine scan memory 30 based on the input low-resolution image data. Of the high-resolution image data (the image data input from the film scanner 12 by performing the fine scan, or the image data input from the media driver 14, or the image data input from the image data receiving device 16) The processing conditions of various image processing performed by the second image processing unit 36 are automatically determined by calculation (setup calculation),
The determined processing conditions are notified to the first image processing unit 32.

The image processing executed by the second image processing section 36 includes, for example, gray balance adjustment of an image,
Image processing for improving the image quality of output images, such as density adjustment, gradation control, hypertone processing for compressing the gradation of the ultra-low frequency luminance component of the image, and hypersharpness processing for enhancing sharpness while suppressing graininess. Can be Further, image processing for intentionally changing the image tone (for example, image processing for finishing the output image in a portrait tone) or image processing for processing the image (for example, a person existing in the original image is narrowed on the main image) Image processing such as image processing for finishing) may be executable.

The first image processing section 32 performs processing on the low-resolution image data stored in the pre-scan memory 28 based on the processing conditions notified from the setup operation section 34 and performs the second image processing on the high-resolution image data. Image processing equivalent to the image processing performed by the image processing unit 36 is performed on the low-resolution image data to generate simulation image data. The first image processing unit 32 includes a color reproduction conversion unit 3
8, the CRT 20 is connected in order, and the simulation image data generated by the first image processing unit 32 is output to the color reproduction conversion unit 38.

The color reproduction converter 38 converts the image represented by the input image data into an output image (an image visualized on photographic paper in an output format for recording an image on photographic paper, a CD-R
A tone conversion look for converting the tone of the input image data so that it is properly reproduced on an image displayed on the CRT 20 using the image data recorded in the output format in which the image data is recorded. Up table (LUT)
40, a color correction three-dimensional lookup table (3D-LUT) 42 for correcting a change in image quality due to gradation conversion in the gradation conversion LUT 40, and a selector 44 are sequentially connected. CR at output
T20, laser printer 22, and CD-R writing device 24
Are connected to each other.

The gradation conversion LUT 40 corresponds to the conversion means of the present invention, and the color correction 3D-LUT 42
Along with the setup calculation unit 34 for setting color correction data (details will be described later) in the 3D-LUT 42 for color correction, it corresponds to the control means of the present invention.

The simulated image data output from the first image processing unit 32 is output to the CRT 20 after being subjected to color reproduction conversion processing such as gradation conversion (details will be described later) by the color reproduction conversion unit 38, and is simulated. The image is displayed on the CRT 20 as an image (output image). The output image displayed on the CRT 20 is used by an operator for verification of image finish and the like.

Further, a key correction input unit 48 is connected to the setup calculation unit 34. This key correction input section 4
8 can be composed of, for example, a keyboard and a mouse connected to the input / output port of the microcomputer. The operator who has verified the output image displayed on the CRT 20 operates the key correction input unit 48 and inputs the verification result. Then, when the processing conditions are determined through the verification by the operator, the setup calculation unit 34 notifies the second image processing unit 36 of the determined processing conditions. Note that the key correction input sections 48 correspond to the specifying means of the present invention, respectively.

The second image processing section 36 includes a plurality of types of image processing circuits for performing the above-described various types of image processing. The second image processing section 36 outputs high-resolution image data from the image data preprocessing section 26 via the fine scan memory 30. Is input, various image processing is performed on the input high-resolution image data in accordance with the processing conditions notified from the setup calculation unit 34. The second image processing unit 36 is connected to the color reproduction conversion unit 38, and the image data output from the second image processing unit 36 undergoes color reproduction conversion processing in the color reproduction conversion unit 38, Or CD-R writing device 24
And is used for recording an image on photographic paper by the laser printer 22 or written on a CD-R by the CD-R writing device 24.

The laser printer 22 has an RGB laser light source. The laser printer 22 modulates the RGB laser light emitted from the laser light source based on the image data input from the image processing device 18, An image is exposed and recorded on the photographic paper by being deflected by a deflecting means such as a mirror and scanned on the photographic paper. The photographic paper on which the image has been exposed and recorded is sent to a processor unit (not shown), and subjected to color development, bleach-fix, washing, and drying. As a result, the image recorded on the photographic paper by exposure is visualized.

Next, the operation of the present embodiment will be described with reference to the flowchart of FIG. 2 showing the setup processing executed by the CPU of the setup calculation section 34.
This setup process is performed in the pre-scan memory 28
Each time the low-resolution image data of a single image is stored in the setup calculation unit 34 (CPU).

In step 100, the pre-scan memory 2
The low-resolution image data stored in the image data 8 is fetched to extract a main part (for example, a region corresponding to a person's face (face region)) in the image and to calculate various image feature amounts. Perform analysis. Also, in step 102, based on the result of analyzing the image data in step 100, the optimum processing conditions of the image processing to be executed by the second image processing unit 36 on the high-resolution image data are calculated, and the calculated processing is performed. The condition is notified to the first image processing unit 32.

In the next step 104, gradation conversion data for performing gradation conversion is set in the gradation conversion LUT 40, and color correction data for performing color correction is set in the color correction 3D-LUT 42. A gradation conversion condition setting process is performed. This gradation conversion condition setting processing will be described with reference to the flowchart in FIG.

In this embodiment, the setup operation section 34
Of the gradation conversion LUT 40 in the storage unit 50 composed of
At least, as the gradation conversion data for setting
Gradation conversion data representing standard gradation conversion conditions (standard gradation conversion conditions) is stored in advance. Further, when the gradation of the image data is converted, the saturation or hue of the image represented by the image data changes. For this reason, in the present embodiment, the 3D-L for color correction is used.
When an image is output using at least image data whose gradation has been converted under standard gradation conditions as color correction data to be set in the UT 42, the image is reproduced as an image having appropriate saturation and hue on the output image. The color correction data representing the color correction conditions (color conversion characteristics) determined so as to correspond to the gradation conversion data representing the standard gradation conversion conditions is stored in the storage unit 50.
Is stored in Note that the storage unit 50 corresponds to the first storage unit and the second storage unit according to the present invention, respectively.

The color correction conditions (color conversion characteristics) represented by the color correction data include, for example, converting the gradation of image data representing a known Macbeth chart in accordance with standard gradation conversion conditions, and converting the image data after gradation conversion. Using a laser printer 22, an image (Macbeth chart) is exposed and recorded on photographic paper by using the laser printer 22, and the saturation and hue of each patch of the Macbeth chart formed on the photographic paper are evaluated. It can be determined to be. Macbeth charts include patches of various colors that frequently appear as subject colors (for example, a plurality of gray patches having different lightness, patches of R, G, B, C, M, and Y, DarkSkin, LightSki).
n, BlueSky, Foliage, etc.) in a well-balanced manner, and the image quality of an image can be properly evaluated with a small number of patches.

In this embodiment, as the image output format, the image display on the CRT 20 (monitor display), the recording of the image on photographic paper by the laser printer 22 (print output), and the CD-R writing device 24 There are three types of output formats for writing image data to a CD-R (CD-R writing). Among these, the monitor display is used to test the image quality of the image to be printed out in advance. It is required that the image displayed on the monitor has the same image quality as the image output on the print.

Since image data written on a CD-R is also generally used for display on a CRT monitor, the image data is displayed on the CRT monitor without any special post-processing when displayed on the CRT monitor. It is desirable that the image be displayed with favorable image quality. For this reason, in the present embodiment, color correction data for monitor display and CD-R writing and color correction data for print output are separately defined as color correction data corresponding to the standard gradation conversion conditions. Alternatively, a color space conversion for making the output image have the same image quality as the print output at the time of CD-R writing is included.
When setting the color correction data in the color correction 3D-LUT 42, the color correction data corresponding to the output format is set in the color correction 3D-LUT 42.

In order to reduce the data amount of the conversion data to be stored, the 3D-LUT usually has the vertices (grid points) of each grid when the data space of the data to be converted is divided into a large number of grids. Is stored, and when data corresponding to between grid points is input, corresponding conversion data is obtained by interpolation from the conversion data of surrounding grid points and output. For this reason, in this embodiment, only the conversion data corresponding to the grid points is set as the color correction data.

In step 150 of the gradation conversion condition setting process, an operator is inquired as to whether or not to perform gradation conversion using the standard gradation conversion conditions by displaying a predetermined message on the CRT 20 or the like. Then, based on the information input by the operator via the key correction input unit 48, it is determined whether or not to perform the gradation conversion using the standard gradation conversion conditions. Initially, when the standard gradation conversion condition is selected by the operator, the determination in step 152 is affirmed, and the process proceeds to step 152, where gradation conversion data representing the standard gradation conversion condition is fetched from the storage unit 50 and fetched. The grayscale conversion data is set in the grayscale conversion LUT 40.

In the next step 154, the color correction data stored in correspondence with the gradation conversion data representing the standard gradation conversion conditions is read out from the storage unit 50, and the color correction data is read.
LUT 42 is set. Thereby, the color reproduction conversion unit 38
Can be subjected to gradation conversion under standard gradation conversion conditions without causing a change in image quality, such as a change in saturation or hue, for the image data input to. And 3D-L for color correction
The image data input from the UT 42 to the selector 44 is C
The selector 44 is switched so as to be output to the RT 20,
The process proceeds to step 106 of the setup process (FIG. 2).

In step 106, the low-resolution image data stored in the pre-scan memory 28 is
The image processing unit 32 executes various image processing, and the color reproduction conversion unit 38 performs color reproduction conversion processing (gradation conversion processing by the gradation conversion LUT 40 and color correction
Color correction processing by the D-LUT 42).

As a result, the first image processing section 32 fetches the low-resolution image data from the pre-scan memory 28, and performs the second image processing on the high-resolution image data based on the processing conditions notified by the processing of the previous step 102. The image processing unit 36 performs image processing equivalent to the image processing performed on the low-resolution image data to generate simulation image data. The simulated image data generated by the first image processing unit 32 includes a gradation conversion LUT 40 and a color correction 3D-LUT of the color reproduction conversion unit 38.
At 42, a color reproduction conversion process is performed.

In step 108, the image data that has undergone the color reproduction conversion processing by the color reproduction conversion section 38 is output to the CRT 20, and the image represented by the image data is displayed on the CRT 20 as an output image. Further, a message requesting verification of the output image displayed on the CRT 20 is displayed together with the CRT 20, and the operator verifies the finish of each part of the output image displayed on the CRT 20.

When the output image is displayed on the CRT 20 and a test for the output image is requested, the operator can use the CRT 2
The output image displayed at 0 is visually checked to determine whether the image quality of the output image is appropriate, that is, whether the processing conditions calculated by the setup calculation unit 34 are appropriate, and whether the gradation expression of the output image is appropriate. A test is performed to determine whether or not the information is valid, and information representing the test result is input via the key correction input unit 48.

When the operator inputs the information indicating the test result via the key correction input unit 48, the process shifts to step 110, and the information indicating the test result input by the operator via the key correction input unit 48 indicates "test OK". It is determined whether the information is meaningful. If the information indicating “test OK” has been input, the above determination is affirmed and the process proceeds to step 116. However, as information representing the test result, information instructing correction of image processing conditions or gradation conversion condition When the information for instructing the correction is input, it is determined that the test result by the operator is “test NG”, and the process proceeds to step 112.

In step 112, it is determined whether or not the information indicating the input test result is information instructing correction of the gradation conversion condition. When the information for instructing the correction of the processing conditions of the image processing is input, the determination in step 112 is denied, and the process proceeds to step 114, in which the input of the processing conditions of the image processing calculated in step 102 is input. And returns to step 106 after notifying the first image processing unit 32 of the corrected processing condition.

Thus, in the first image processing section 32,
A process of regenerating the simulation image data according to the corrected processing conditions is performed, and the regenerated simulation image data is output to the CRT 20 through the color reproduction conversion process in the color reproduction conversion unit 38, so that the input correction instruction CRT based on the processing conditions corrected according to
The output image is displayed again at 20. By visually checking the output image redisplayed on the CRT 20, the operator can easily determine whether or not the content of the previously input correction instruction is appropriate.

On the other hand, when it is determined that the gradation expression is not appropriate for the output image displayed on the CRT 20, the operator inputs a gradation conversion condition other than the standard gradation conversion condition via the key correction input unit 48. Enter information to instruct use.
In this case, the determination in step 112 is affirmed, and the process returns to step 104, where the gradation conversion condition setting process (FIG. 3) is executed again.

In the gradation conversion condition setting processing, information for instructing the use of gradation conversion conditions other than the standard gradation conversion conditions is input, so that the determination at step 150 is denied, and the routine proceeds to step 156, where Is displayed on the CRT 20 to ask the operator whether or not the tone conversion conditions obtained by correcting the currently set tone conversion conditions are to be used for tone conversion. Branches the process based on the information input via the key correction input unit 48. If correction of the currently set gradation conversion condition is instructed, step 156 is executed.
From step to step 158, and displays a gradation conversion condition correction screen for the operator to instruct correction of the gradation conversion condition.
Display at T20.

As an example, as shown in FIG. 4, the gradation conversion condition correction screen changes the entire density range from highlight to shadow of the image into three density ranges (highlight range, halftone range and shadow range). Buttons for "high contrast", "no correction", and "soft" are provided for each density region when divided, and the operator operates a mouse or the like of the key correction input unit 48 and clicks a desired button. By doing so, it is possible to arbitrarily instruct the correction of the gradient (γ) of the gradation conversion condition for each density area (the number of divisions of the entire density area may be more or less than three, A single inclination may be set for the whole). In the next step 160, it is determined whether or not the input of the information for correcting the gradation conversion condition is completed, and the process waits until the input is completed.

Thus, the operator operates the key correction input unit 48 to obtain the optimum gradation conversion condition (desired gradation conversion condition) according to the type of the subject existing in the image and the use of the image. Thus, the currently set gradation conversion condition can be arbitrarily corrected. When the operator completes the input of the information for correcting the gradation conversion condition, the determination in step 160 is affirmed, and step 162 is performed.
Then, the conversion data representing the correction target gradation conversion condition (the currently set gradation conversion condition) is corrected in accordance with the correction instruction input by the operator.

For example, a gradation conversion condition as shown in FIG. 5A is set as the gradation conversion condition.
As shown in (B), when “high contrast” is selected for the highlight region, “soft gradation” for the halftone region, and “no correction” for the shadow region, correction of the gradation conversion condition is not performed. 5C can be performed by superimposing (cascading) the currently set gradation conversion condition and the gradation conversion condition defined by the input correction instruction. Conversion data representing the gradation conversion conditions as shown by.

When the gradation conversion data representing the gradation conversion condition desired by the operator is obtained as described above, the obtained gradation conversion data is set in the gradation conversion LUT 40. As a result, the image data input to the color reproduction conversion unit 38 is subjected to gradation conversion by the gradation conversion LUT 40 under the gradation conversion conditions desired by the operator.

In the subsequent steps 164 and subsequent steps, as a color correction condition corresponding to the corrected gradation conversion condition, a change in saturation, hue, or the like when gradation conversion is performed using the corrected gradation conversion condition is corrected. Is calculated. That is, in step 164, the input values R1'n, G1'n, G1'n, at the specific grid point (the grid point n) of the 3D-LUT for color correction 42 are set.
B1'n (the input value at each grid point is fixedly determined) is converted to R1
Calculate the GB values (R0n, G0n, B0n).

In the next step 166, the RGB value R
RG when 0n, G0n, B0n are converted under standard gradation conversion conditions
The B values R1n, G1n, and B1n are calculated. In step 168, the RGB values (R2n, G2n, B2n) are calculated when the RGB values R1n, G1n, B1n are corrected (converted) under the color correction conditions corresponding to the standard gradation conversion conditions. And step 17
At 0, the color correction data Rout, Gout, Bout (= R2'n, G2'n, B2'n) representing the color conversion condition at the lattice point n among the color correction conditions corresponding to the corrected gradation conversion condition The calculation is performed according to the following equation. Rout = R2'n = R2n- (R2n + G2n + B2n) / 3 + (R2'n + G2'n + B2'n) / 3 Gout = G2'n = G2n- (R2n + G2n + B2n) / 3 + (R2'n + G2'n + B2'n) / 3 B2'n = B2n- (R2n + G2n + B2n) / 3 + (R2'n + G2'n + B2'n) / 3 In the next step 172, steps 164 to 1
It is determined whether or not the calculation of 70 has been performed for all grid points of the 3D-LUT 42 for color correction. If the determination is negative, the process returns to step 164, and steps 164 to 172 are repeated.

The RGB values R2n, G2 obtained in step 168
n and B2n are RGB values when RGB values (image data) R0n, G0n and B0n are converted according to the standard gradation conversion conditions and further corrected (converted) according to the color correction conditions corresponding to the standard gradation conversion conditions. . On the other hand, the RGB values R2'n,
G2'n and B2'n are the RGB values of the pixels whose brightness is substantially the same as that of the pixels whose RGB values are R2'n, G2'n and B2'n and whose hue is gray (the RGB values are (R2'n + G2 ' n + B2'n) / 3), the ratio of the difference for each RGB is equal to the RGB value R2n, G2n, B2n, so that the pixel of RGB value = R2'n, G2'n, B2'n is RGB.
Pixels having the same saturation and hue as those of the B value = R2n, G2n, B2n pixels are visually recognized.

Therefore, as described above, when the RGB values (image data) R0n, G0n, and B0n are converted according to the corrected gradation conversion conditions, the RGB values R1'n, G1'n, and B1'n are converted into color values. The RGB values R2'n, G2'n, B2'n (= Rout, Gou
3D-LUT for color correction so that it is converted to
By setting color correction data for each of the grid points 42, color correction conditions (color correction data) that can correct changes in saturation, hue, and the like when gradation conversion is performed using the corrected gradation conversion conditions. ) Can be obtained.

When color correction data is set for all grid points, the determination in step 172 is affirmed, and
74, and transfers the obtained color correction data to the 3D-
Set in LUT40. Thereby, the color reproduction conversion unit 38
It is possible to perform gradation conversion on the image data input to the printer under the gradation conversion conditions desired by the operator without causing a change in image quality such as a change in saturation or hue.

As described above, the color correction data corresponding to the standard gradation conversion condition includes monitor display and C
Since there are two types, one for DR writing and one for printing output,
The processing of steps 164 to 172 described above is respectively performed using the above two types of color correction data.
At 74, of the two types of color correction data corresponding to the corrected gradation conversion conditions, the color correction data for monitor display and CD-R writing is set in the color correction 3D-LUT 40.

In the next step 176, the operator determines whether or not to register the corrected tone conversion condition and the color correction condition corresponding to the tone conversion condition in the storage unit 50 by displaying a predetermined message on the CRT 20 or the like. And determines whether or not to register the corrected gradation conversion condition and the corresponding color correction condition in the storage unit 50 based on the information input by the operator via the key correction input unit 48 in response to the inquiry. .

If the determination is negative, the conversion condition setting process ends without performing any processing. If the determination is affirmative, the process proceeds to step 178, where the step representing the corrected gradation conversion condition is performed. The operator inputs the key conversion data and the color correction data representing the corresponding color correction conditions into the key correction input unit 4.
After the registration in the storage unit 50 in association with the registration name input via the control unit 8, the conversion condition setting process is terminated, and the process proceeds to step 106 of the setup process (see FIG. 2). As described above, by registering the newly set tone conversion condition and the corresponding color correction condition this time in the storage unit 50, the tone conversion condition can be used for tone conversion and color correction for image data of another image as described later. Is also possible.

When the use of the gradation conversion conditions already registered in the storage unit 50 is instructed as the gradation conversion conditions other than the standard gradation conversion conditions, the determinations in step 150 and step 156 are respectively made. Step 1 by being denied
80, a list of registered names of all the gradation conversion conditions already registered in the storage unit 50 is displayed on the CRT 20, a predetermined message is displayed on the CRT 20, and the registered gradation is displayed. The operator is requested to select any of the gradation conversion conditions from the conditions. Next step 182
Then, it is determined whether any gradation conversion condition is selected, and
It waits until the determination is affirmed.

According to the message displayed on the CRT 20, the operator operates the CRT 2 via the key correction input unit 48.
When a registered name corresponding to a desired gradation conversion condition is selected from the registered names listed in 0, the determination in step 182 is affirmed, and the process proceeds to step 184, where the floor corresponding to the selected registered name is selected. The gradation conversion data of the gradation conversion condition is fetched from the storage unit 50, and the fetched gradation conversion data is set in the gradation conversion LUT 50. In step 186, the color correction data of the color correction condition corresponding to the gradation conversion condition is fetched from the storage unit 50, and the color correction 3D-LUT
After setting to 42, the conversion condition setting process ends, and the process proceeds to step 106 of the setup process (see FIG. 2).

As a result, the image data input to the color reproduction conversion section 48 is subjected to gradation conversion under the gradation conversion conditions desired by the operator without causing a change in image quality such as a change in saturation or hue. It can be carried out.

Step 106 of the setup process
Then, the first image processing unit 32 regenerates the simulated image data, and the regenerated simulated image data is subjected to the color reproduction conversion processing in the color reproduction conversion unit 38 (a process based on a gradation conversion condition other than the standard gradation conversion condition). Tone conversion, and color correction based on color correction conditions set to prevent a change in image quality such as a change in saturation or hue).
The output image is displayed on the CRT 20 again by being output to the RT 20. By visually checking the tone expression in the output image redisplayed on the CRT 20, the operator can easily determine whether the current tone conversion condition is appropriate.

The operator judges that the image quality of the output image displayed on the CRT 20 is appropriate, and inputs information indicating “test OK” as information indicating the test result to the key correction input unit 4.
8, the determination in step 110 is affirmed, and the process proceeds to step 116, where the determined processing condition (first
Out of the latest processing condition notified to the image processing unit 32, the gradation conversion condition (gradation conversion data) set in the gradation conversion LUT 40, and the two types of color correction data corresponding to the gradation conversion condition. Color correction data corresponding to the image output format (color correction data for print output if the output format is print output, monitor display and CD-R write colors if the output format is monitor display or CD-R writing) The correction data) is temporarily stored in the storage unit 50 in association with the image identification information (for example, the frame number) for identifying the target image (the image on which the operator has performed the test), and the setup processing ends.

When the high-resolution image data of the image to be output in the designated predetermined output format is output from the image data preprocessing unit 26 and stored in the fine scan memory 30 after the completion of the setup processing, the setup operation is performed. The unit 34, based on the image identification information of the image represented by the high-resolution image data stored in the fine scan memory 30,
The processing condition information corresponding to the high-resolution image data is read from the storage unit 50, and the read processing condition information is output to the second image processing unit 36 to instruct execution of image processing.

When reading out the processing condition information from the storage unit 50, the setup calculation unit 34 stores the gradation conversion data and the color correction data (output image data) corresponding to the image identification information and the processing condition information. The color correction data corresponding to the format is also read from the storage unit 50, the read gradation conversion data is set in the gradation conversion LUT 40, and the read color correction data is stored in the 3D-LUT 4 for color correction.
The selector 44 is switched so that the image data input to the selector 44 is output to an output device (the laser printer 22 or the CD-R writing device 24) corresponding to the output format of the image.

Thus, in the second image processing unit 36,
The high-resolution image data is read from the fine scan memory 30, subjected to various image processing according to the processing conditions represented by the processing condition information input from the setup operation unit 34, and then output to the color reproduction conversion unit 38.

The second image processing unit 36 to the color reproduction conversion unit 3
8, the high-resolution image data is input to the LU for gradation conversion.
L for gradation conversion according to the gradation conversion data set in T40
The gradation conversion is performed by the UT 40, and the color correction 3D-L
3D for color correction according to color correction data set in UT42
After the color correction is performed by the LUT 42, the image is output to an output device corresponding to a predetermined output format, and is recorded as an image on photographic paper by the laser printer 22, or
The data is written to the CD-R by the DR writing device 24.

As a result, an output image (an image recorded on a photographic paper or a C
The image displayed on the CRT using the image data recorded on the DR is also converted in gradation according to an instruction from the operator, and the image quality may change due to a change in saturation or hue. Is prevented.

In the above description, gradation conversion is performed using a one-dimensional LUT.
However, the present invention is not limited to this. For example, a 3D-LUT is provided as an LUT for gradation conversion, and gradation conversion is performed independently for each color component (for example, R, G, B). You may.

In the above description, the case where the gradation conversion is performed by the gradation conversion LUT 40 and the color correction is performed by the color correction 3D-LUT 42 is described. However, the present invention is not limited to this. The conversion data representing the conversion characteristic obtained by superimposing the specified gradation conversion condition and the color correction condition specified by the color correction data is converted into a single 3D-L.
By setting the UT and converting the image data by the single 3D-LUT, gradation conversion and color correction may be performed simultaneously.

Further, in the mode in which the gradation conversion and the color correction are simultaneously performed by the single 3D-LUT as described above, only the pixels having the hue of gray or close to gray in the input image data are designated. By setting conversion data for performing tone conversion in accordance with the tone conversion characteristics, it is also possible to realize tone conversion with an arbitrary tone conversion characteristic without causing a change in saturation or hue.

The correction of the change in the ratio of the difference of each color component to the gray of each pixel of the image data is performed by converting the image data using the multidimensional lookup table as described above. The correction (reconversion of image data) is performed by, for example, substituting the value of each color component of each pixel of image data into a conversion expression expressing a desired conversion characteristic by a function or the like. Is also good.

[0089]

As described above, according to the present invention, the conversion characteristic of the conversion means is controlled so that the gradation of the image data is converted according to the specified conversion characteristic, and the image data is converted according to the specified conversion characteristic. Re-converting the image data that has been converted by the conversion means, so that the change in the ratio of the difference of each color component with respect to the gray of each pixel of the image data is accompanied by the conversion of the gradation, or Since the conversion characteristic of the conversion means is controlled, there is an excellent effect that a change in image quality due to grayscale conversion can be accurately corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an image processing system according to an embodiment.

FIG. 2 is a flowchart showing the contents of a setup calculation process executed by a setup calculation unit.

FIG. 3 is a flowchart showing the contents of a conversion condition setting process.

FIG. 4 is an image diagram showing an example of a gradation conversion condition correction screen.

FIG. 5 is a diagram for explaining correction of a gradation conversion condition.

[Explanation of symbols]

 Reference Signs List 10 image processing system 34 setup operation unit 38 color reproduction conversion unit 40 gradation conversion LUT 42 3D-LUT for color correction 48 key correction input unit 50 storage unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/46 H04N 1/46 Z F-term (Reference) 2C262 AA24 AB13 AC05 BA20 BB03 BB15 BC01 BC07 BC10 5B057 BA02 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CE11 CE17 CH07 5C077 LL19 MP08 NP05 PP15 PP21 PP32 PP37 PP47 PQ08 PQ12 PQ22 PQ23 SS05 SS06 TT03 TT09 5C079 HB01 JA11 JA23 LA12 LA31 LB01 MA01 MA03 NA03 NA03

Claims (11)

[Claims] A conversion unit for converting image data; a specification unit for specifying conversion characteristics of gradation conversion for the image data; and a conversion unit in which the gradation of the image data is specified via the specification unit. The conversion characteristics of the conversion means are controlled so as to be converted according to the characteristics, and the gradation of the image data is converted according to the specified conversion characteristics. An image processing apparatus comprising: a control unit that re-converts image data that has been converted by the conversion unit or controls a conversion characteristic of the conversion unit so that a change in a difference ratio is corrected. 2. The image data is obtained by irradiating light on a photographic film and converting light transmitted through an area on the photographic film where an image is recorded into an electric signal by a photoelectric conversion sensor. The image processing apparatus according to claim 1, wherein 3. The image processing apparatus according to claim 1, wherein the control unit converts each color component value of each pixel of the image data obtained by converting the image data whose gradation is converted in accordance with the specified conversion characteristic into R2 ′, G2 ′, and B2.
2 ′, when each color component value of each pixel of the image data obtained by converting the image data whose gradation is not converted is R2, G2, B2, R2 ′ − (R2 ′ + G2 ′ + B2 ′) / 3 ≒ R2 − (R2 + G
2 + B2) / 3 G2 '-(R2' + G2 '+ B2') / 3 @ G2- (R2 + G
2 + B2) / 3 B2 '-(R2' + G2 '+ B2') / 3 @ G2- (R2 + G
2. The image processing apparatus according to claim 1, wherein re-conversion of the image data or control of a conversion characteristic of the conversion unit is performed according to a conversion characteristic satisfying 2 + B2) / 3. 4. The control means includes a multi-dimensional look-up table, wherein the conversion means converts the gradation of the image data to the ratio of the ratio of the difference of each color component to the gray of each pixel of the image data. The conversion data set so that the change is corrected is set in the multi-dimensional lookup table, and the multi-dimensional lookup table in which the conversion data is set is used to re-convert the image data that has been converted by the conversion unit. The image processing apparatus according to claim 1, wherein: 5. The conversion means converts image data using a multi-dimensional look-up table, and the control means converts a conversion characteristic designated through the designation means and a gradation of the image data according to the conversion characteristic. By setting conversion data of conversion characteristics obtained by superimposing conversion characteristics and a conversion characteristic for correcting a change in the ratio of a difference of each color component with respect to gray of each pixel of the image data of the converted image data in the multidimensional lookup table, 2. The image processing apparatus according to claim 1, wherein a conversion characteristic of the conversion unit is controlled. 6. The multi-dimensional look-up table converts the image data according to the conversion unit, and the control unit sets the data corresponding to an achromatic portion of the image data input to the multi-dimensional look-up table. The conversion characteristic of the conversion unit is controlled by setting conversion data of the conversion characteristic for converting only the conversion characteristic according to the conversion characteristic specified via the specifying unit in the multidimensional lookup table. The image processing device according to claim 1. 7. The image processing apparatus according to claim 1, wherein a slope of the conversion characteristic is specified as the conversion characteristic of the gradation conversion for the image data via the specifying unit. 8. A conversion characteristic of gradation conversion for the image data is specified independently by the specifying unit in units of each range when a range from highlight to shadow is divided into a plurality of ranges. The image processing apparatus according to claim 1, wherein: 9. A method according to claim 1, further comprising: a first storage unit that stores a plurality of types of conversion characteristics, wherein a specific conversion characteristic is selected from the plurality of types of conversion characteristics stored in the first storage unit via the specifying unit. 2. The image processing apparatus according to claim 1, wherein the selection specifies a conversion characteristic of gradation conversion for the image data. 10. The apparatus according to claim 1, further comprising a second storage unit configured to store the conversion characteristic specified via the specification unit, wherein a correction to the conversion characteristic stored in the second storage unit is instructed via the specification unit. 2. The image processing apparatus according to claim 1, wherein a conversion characteristic of gradation conversion for the image data is designated. 11. When a conversion characteristic of gradation conversion for image data is designated via a designation unit, the gradation of the image data is converted according to the conversion characteristic designated via the designation unit. While controlling the conversion characteristics of the conversion to the image data, the change in the ratio of the difference of each color component to the gray of each pixel of the image data due to the conversion of the gradation of the image data according to the specified conversion characteristics An image processing method for re-converting the converted image data or controlling a conversion characteristic of the conversion of the image data so as to be corrected.