JP2001061074A - Color correction method and device and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain color correction similar to the case with analog printing when a color of digital image data is corrected and printed out. SOLUTION: A 3D LUT where a value of image data S0 is made to correspond to a colorimetric value of an analog print is generated for all combinations of densities able top be set by each color tone adjustment of a key correction means 6 and stored in a database 7. In the case that an image processing means 2 applies color correction to the image data S0 obtained by an image entry means 1, a 3D LUT in response to the entry of a key correction means 6 is selected from the database 7 and the image processing means 2 applies the color correction processing to the image data S0 according to the selected 3D LUT to obtain processed image data S1 and an image output means 3 prints out the data S1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color correction for performing color correction processing on image data so as to have a desired color when digital image data representing a color image read from a film or the like is printed out. The present invention relates to a computer-readable recording medium on which a program for causing a computer to execute a method and apparatus and a color correction method is recorded.

[0002]

2. Description of the Related Art Conventionally, printing of an image recorded on a negative film or a reversal film onto a photosensitive material is performed by a so-called analog exposure in which an image of the film is projected on the photosensitive material and the photosensitive material is surface-exposed. Yes,
An analog printer is used to perform such analog exposure.

On the other hand, in recent years, an image recorded on a film is photoelectrically read to obtain digital image data representing the image, and after performing various image processings on the image data, the image data is processed. 2. Description of the Related Art Digital printers have been used in which a photosensitive material is scanned and exposed by a modulated recording light to record an image on the photosensitive material and print out the image. In digital printers, it is possible to easily correct jumping or crushing of images due to backlight or strobe shooting, and to perform various image processing such as frequency processing and density conversion processing. Can obtain a high-quality print image that could not be obtained.

Here, the image processing performed in the digital printer includes a gray balance adjustment table and a gray balance adjustment table as described in JP-A-11-91169.
A one-dimensional correction table such as a contrast correction table and a brightness correction table, and a matrix for correcting saturation are prepared in advance, and brightness adjustment keys, C,
The user performs key input from key input means provided with a color adjustment key for each color of M and Y, a contrast adjustment key, and the like, and changes the inclination of the one-dimensional correction table based on the key input, and corrects a matrix operation. For example, image processing is performed on the image data so as to obtain a desired image. Then, the processed image data is color-converted by a three-dimensional color conversion table set according to the number of times of input of each color adjustment key, and printed out. In this key input, the setting is made such that the inclination of the table and the density of the output color are changed by one step each time the key is pressed once.

An analog printer can perform color conversion and print out an image. In this case, a color correction filter is used to change the amount of light of each color that exposes the photosensitive material. This color correction filter has a plurality of density filters (here, the filter densities are represented by +1, +2,...) Arranged for each color on a disk as shown in FIG. By exposing the photosensitive material by switching the filters located on the optical path of the printing light, the density of the color corresponding to the filters in the print image can be corrected.

[0006]

By the way, considering the wavelength of light, a color correction filter in an analog printer cannot correct each color completely independently because it has not only main absorption but also illegal absorption. On the contrary,
In a digital printer, a signal value constituting each color of image data is processed, so that each color can be completely independently corrected. Therefore, even if the same color correction is performed, the density of the obtained image differs between the print image obtained by the analog printer and the print image obtained by the digital printer. For example, when the density of C (cyan) is corrected from +3 to +4, that is, when the density is corrected from C + 3 to C + 4, the number of times of inputting the color correction key of C is changed from three times to four times. There is no difference in operation. First, considering only the analog printer, as shown in FIG. 5A, the C + 4 color correction filter has a lower filter density D (λ) than the C + 3 color correction filter, so that the amount of transmitted light of the filter increases. As shown in FIG. 6A, the exposure amount P (λ) for the photosensitive material increases. Here, each dye in the photosensitive material is sensitive to light of a complementary color. For example, the C dye emits C color in response to R light. Therefore, FIG.
For a photosensitive material having a spectral sensitivity as shown in FIG.
When the exposure is performed with the exposure amount as shown in FIG. 8A, the exposure amount × the spectral sensitivity of the photosensitive material has the characteristic shown in FIG. 8A, and on the photosensitive material, as shown by the broken line in FIG. As shown by the solid line in FIG. 9, not only the color of C but also the colors of Y and M are generated due to the influence of the Y and M dyes.

On the other hand, considering a digital printer, when correcting the density of C from +3 to +4, FIG.
As shown in FIG. 6B, the output value with respect to the input value increases, and as a result, the exposure amount P (λ) for the photosensitive material increases as shown in FIG. 6B. Therefore, for a photosensitive material having a spectral sensitivity as shown in FIG. 7, FIG.
When exposure is performed with an exposure amount as shown in FIG. 8, the exposure amount × the spectral sensitivity of the photosensitive material has the characteristic shown in FIG. Here, comparing FIG. 8A and FIG. 8B, the digital printer has no illegal absorption for the other dyes Y and M at all. Therefore, in the photosensitive material, as shown by the dashed line in FIG.
Color hardly develops, and although the same processing is performed by the analog printer and the digital printer, the density of the color developed on the photosensitive material is different between the two. .

The present invention has been made in view of the above circumstances, and a color correction method and apparatus capable of performing the same color correction as in the case of printing and outputting in an analog printer when printing and outputting digital image data. It is an object of the present invention to provide a computer-readable recording medium on which a program for causing a computer to execute a color correction method is recorded.

[0009]

According to the color correction method of the present invention, when digital image data representing a color image is printed out, the digital image data is subjected to color correction processing to obtain processed image data. In the color correction method, a data value of image data obtained by photoelectrically reading a film on which an image for creating an analog print is recorded, and a color correction process performed by performing different color correction processing on the image data. From a plurality of color conversion tables representing a relationship with colorimetric values of a plurality of analog prints, a desired color conversion table is selected, and the digital image data is color-converted based on the selected color conversion table. It is characterized by obtaining processed image data.

[0010] In the color correction method according to the present invention, it is preferable that the desired color conversion table is selected based on an input result input from key means for correcting each color of the color image.

In a color correction apparatus according to the present invention, when digital image data representing a color image is printed out, the color correction apparatus performs a color correction process on the digital image data to obtain processed image data. Data values of image data obtained by photoelectrically reading a film on which an image to be printed is recorded and measurement of a plurality of analog prints obtained by performing different color correction processing on the image data. Storage means for storing a plurality of color conversion tables representing a relationship with color values; selecting means for selecting a desired color conversion table from the storage means; and the digital image data based on the selected color conversion table. And color correction means for converting the color data to obtain the processed image data.

In the color correcting apparatus according to the present invention, the selecting means includes a key means for correcting each color of the color image, and based on an input result inputted from the key means, the selection means is selected. It is preferable to use a means for selecting a color conversion table to be used.

Note that the program for causing a computer to execute the color correction method according to the present invention may be provided by being recorded on a computer-readable recording medium.

[0014]

According to the present invention, a data value of image data obtained by photoelectrically reading a film on which an image for forming an analog print is recorded and a different color correction process are performed on the image data. A plurality of color conversion tables representing the relationship with the colorimetric values of a plurality of analog prints obtained by performing the application are created in advance, and a digital image is formed by a desired color conversion table selected from the plurality of color conversion tables. The color conversion of data is performed to obtain color-corrected processed image data. For this reason, the color of the image obtained by printing out the processed image data can be the same color as when the color image is analog-printed, and analog printing can be performed on digital image data. The same color correction can be performed as when performing the correction.

Further, by selecting a desired color conversion table based on the input result input from the key means, it is possible to perform color correction by the same operation as in the prior art.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram showing a configuration of an image output system to which a color correction device according to an embodiment of the present invention is applied. As shown in FIG. 1, the image output system according to the present embodiment includes an image input unit 1 that photoelectrically reads a color image recorded on a film and obtains digital image data S0 representing the color image, and an image data S0. An image processing unit 2 that performs color correction processing on the image data to obtain processed image data S1, an image output unit 3 that prints out the processed image data S1, and a monitor 5 that displays the image data S0 and S1. , Image processing means 2 as will be described later.
And a database 7 storing a plurality of three-dimensional lookup tables (hereinafter referred to as 3DLUTs) in which data values of image data S0 and colorimetric values of analog print are associated with each other. Is provided.

The image input means 1 photoelectrically reads a negative film, a reversal film, or the like on which an image is recorded, and obtains digital image data S0 comprising an RGB luminance signal or a CMY density signal.

The image processing means 2 has a 3D LU stored in a database 7 in accordance with an input result from the key correcting means 6.
T is selected, and image data S is selected by the selected 3DLUT.
0 is color-converted to obtain processed image data S1. Note that various image processing such as gray balance adjustment processing, frequency emphasis processing, and gradation conversion processing may be performed on the processed image data S1 as needed.

The image output means 3 outputs the processed image data S
1, the laser light provided for each of the RGB colors for exposing the photosensitive material is modulated to process the processed image data S1.
Is recorded on a photosensitive material to output a print image.

The monitor 5 converts the image data S0 and S1 into image data for monitor display and displays the image data.
By displaying the processed image data S1, it is possible to confirm whether or not the color correction processing has been appropriately performed on the image data S0.

The key correction means 6 is for inputting keys so that the image displayed on the monitor 5 has been subjected to the desired color correction processing. The key correction means 6 is, for example, as shown in FIG.
In addition to the adjustment keys 11, 12, and 13 for the 0, C, M, and Y colors and the contrast adjustment key 14, there are provided keys (not shown) for performing various inputs. Brightness, color, contrast, and the like are changed by one step. For example, if the C color adjustment key 11 is pressed twice, the density of C is increased by two levels. If the color adjustment range is five levels for each color, the color adjustment key 1
If 1, 12, 13 is pressed five or more times, the process returns to the first stage from the fifth stage.

3DLUT stored in database 7
Is for associating the data value of the image data S0 with the colorimetric value of the analog print. The 3DLUT includes a data value of image data obtained by photoelectrically reading a film on which an image for creating an analog print is recorded, and a plurality of data values obtained by performing different color correction processing on the image data. Are created in advance based on the relationship with the colorimetric values of the analog print of
Is stored. Specifically, 3DLUT is
The color data of the analog prints obtained in all the combinations that can be set with the adjustment keys for each color is measured by a colorimeter, and the image data S0 read by the image input unit 1 is measured.
Of the image data S0, the density of the color correction filter when performing analog printing, the exposure amount to the photosensitive material, and the spectral sensitivity of the photosensitive material. And the like. Then, by converting the image data S0 using the 3DLUT, it is possible to obtain processed image data S1 capable of reproducing an image subjected to color correction similar to that obtained in analog printing. The 3DLUT has adjustment keys 11, 12, 1 for each color.
All combinations that can be set in 3 are stored in the database 7. For example, if each of the C, M, and Y colors can be adjusted in five steps, 5 ³ =
125 kinds of 3DLUTs are stored in the database 7.

Next, the operation of this embodiment will be described. FIG. 3 is a flowchart showing the operation of the present embodiment. First, an image recorded on a film is photoelectrically read by the image input means 1 to obtain image data S0 (step S1). The image data S0 is input to the image processing means 2 and displayed as a visible image on the monitor 5 (step S2). Next, it is determined whether or not the color adjustment keys 11, 12, and 13 for performing color correction have been input (step S3), and the color adjustment keys 11, 12, and 1 are determined.
If there is an input of 3 and step S3 is affirmed,
A 3D LU corresponding to the number of inputs of each color adjustment key 11, 12, 13 from a plurality of 3D LUTs stored in the database 7
T is selected (step S4), and the selected 3DLUT
Performs color correction on the image data S0 (step S5). The processed image data S1 obtained by performing the color correction is displayed on the monitor 5 (step S5).
6) By checking the image displayed on the monitor 5 by the operator, it is determined whether or not a color correction process has been performed to obtain an image of a desired color. If the color correction processing is appropriate, the effect is input from the key correction means 6 (step S7), and the processed image data S1 is input.
After the necessary image processing has been performed on the
8) The printout is performed by the image output means 3 (step S9), and the process is terminated.

On the other hand, if step S7 is denied, the process returns to step S3, and the processing from step S3 to step S7 is repeated until step S7 is affirmed. If step S3 is denied, the 3DLUT corresponding to the case without key input is selected from the plurality of 3DLUTs stored in the database 7 (step S1).
0) Then, the processes from step S5 to step S9 are performed, and the printout is performed.

As described above, in the present embodiment, a plurality of 3DLUTs representing the relationship between the data value of the image data S0 and the colorimetric values of the analog print are created in accordance with the degree of color correction and stored in the database 7. In addition, color correction of the digital image data S0 is performed by the 3DLUT selected according to the degree of color correction determined according to the number of times of input of the adjustment keys 11, 12, and 13 of each color, and the processed image data S
1 is obtained, the color of the image obtained by printing out the processed image data S1 by the same operation as in the related art can be made the same color as when the image is analog-printed. The same color correction can be performed on the image data S0 as when analog printing is performed.

In the above embodiment, the image processing means 2 performs image processing in addition to the color correction processing. However, another image processing means for performing image processing is provided. May perform necessary image processing. In this case, the image processing may be performed on the image data S0 or the processed image data S1.

In the above embodiment, the 3DLUT is selected according to the key input of the key correction means 6,
However, the present invention is not limited to this. For example, another input means such as a keyboard and a mouse may be provided, and the 3DLUT may be selected in accordance with an input from the other input means.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram illustrating a configuration of an image output system to which a color correction device according to an embodiment of the present invention is applied.

FIG. 2 is a diagram showing a configuration of a key correction unit.

FIG. 3 is a flowchart showing the operation of the embodiment.

FIG. 4 is a diagram showing a color correction filter.

FIG. 5 is a diagram illustrating filters and tables selected when different color correction processes are performed in an analog printer and a digital printer.

FIG. 6 is a diagram illustrating the exposure amount of a photosensitive material when different color correction is performed in an analog printer and a digital printer.

FIG. 7 is a diagram showing the spectral sensitivity of a photosensitive material.

FIG. 8 is a diagram showing an exposure amount × photosensitive material spectral sensitivity when performing different color corrections in an analog printer and a digital printer.

FIG. 9 is a diagram illustrating color density on a photosensitive material when different color correction is performed in an analog printer and a digital printer.

[Explanation of symbols]

 Reference Signs List 1 image input means 2 image processing means 3 image output means 5 monitor 6 key correction means 7 database 11, 12, 13 color correction keys

Continued on front page F-term (reference) 5B057 AA20 CA01 CA08 CA12 CB01 CB08 CB12 CC01 CE17 CH07 CH18 DB02 DB06 DB09 5C077 LL19 MP08 PP37 PQ08 PQ23 SS05 TT10 5C079 HB02 LA31 LB01 MA04 MA19 NA03 PA08

Claims (6)

[Claims] When a digital image data representing a color image is printed out, a color correction method is performed on the digital image data to obtain processed image data. The relationship between the data value of image data obtained by photoelectrically reading a recorded film and the colorimetric values of a plurality of analog prints obtained by performing different color correction processing on the image data is shown. Selecting a desired color conversion table from the plurality of color conversion tables to be represented, and performing color conversion on the digital image data based on the selected color conversion table to obtain the processed image data. Correction method. 2. The color correction method according to claim 1, wherein the desired color conversion table is selected based on an input result input from key means for correcting each color of the color image. . 3. When a digital image data representing a color image is printed out, a color correction apparatus that performs a color correction process on the digital image data to obtain processed image data is provided. The relationship between the data value of image data obtained by photoelectrically reading a recorded film and the colorimetric values of a plurality of analog prints obtained by performing different color correction processing on the image data is shown. Storage means for storing a plurality of color conversion tables to represent, selecting means for selecting a desired color conversion table from the storage means, and performing color conversion on the digital image data based on the selected color conversion table. A color correction unit for obtaining processed image data. 4. The selection means includes key means for correcting each color of the color image, and selects the desired color conversion table based on an input result input from the key means. The color correction device according to claim 3, wherein the color correction device is provided. 5. A program for causing a computer to execute a color correction method for performing color correction processing on digital image data to obtain processed image data when digital image data representing a color image is printed out. In a recorded computer-readable recording medium, the program is a computer-readable recording medium, wherein the data value of image data obtained by photoelectrically reading a film on which an image for creating an analog print is recorded is different from the data value of the image data. A procedure of selecting a desired color conversion table from a plurality of color conversion tables representing a relationship with colorimetric values of a plurality of analog prints obtained by performing the correction processing; and a step of selecting a desired color conversion table based on the selected color conversion table. Color-converting the digital image data to obtain the processed image data. Computer readable recording medium according to. 6. The method according to claim 1, wherein the selecting step is a step of selecting the desired color conversion table based on an input result input from key means for correcting each color of the color image. 6. The computer-readable recording medium according to claim 5, wherein: