JP2002271642A - Image processing method and unit, and recording medium for recording program for carrying out the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing method, by which image processing such a photographing sensitive material is conducted with high accuracy and detailed revision, such as increase/decrease in the saturation with respect to a particular color or the like, can be attained. SOLUTION: The image processing method applies digital image processing to received image data and provides the output of a photographing sensitive material similar to image for the conversion into output image data, uses an image conversion process to approximate image conversion by using a 3DLUT cross-referencing the received image data with the output image data, so as to obtain the photographing sensitive material like image in order to solve the task above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and apparatus, and a recording medium on which a program for executing the method is recorded, and more particularly to a color medium for outputting a multiband image as a photographic material-like image. The present invention relates to an image processing technology and a color matching technology.

[0002]

2. Description of the Related Art Conventionally, in an exposure system in silver halide photographic technology, printing is generally performed by analog exposure (surface exposure). That is, the developed negative film is positioned at a predetermined printing position, irradiated with light from a white light source (such as a halogen lamp), and a transmission image from the negative film is formed on photographic paper and exposed.

On the other hand, in recent years, a printing apparatus utilizing digital exposure, that is, an image recorded on a photographic film such as a negative film or a reversal film is photoelectrically read, and the read image is converted into a digital signal. After that, various image processings are performed to obtain image data for recording, and a photosensitive material is scanned and exposed by a recording light modulated according to the image data to record an image (latent image) to be a (finished) print. Photo printers have been put to practical use.

[0004] In a digital photo printer, an image can be converted into digital image data, and exposure conditions for printing can be determined by digital image processing. By appropriately performing (sharpening) processing, correcting color or density feria, etc., it is possible to obtain high-quality prints that cannot be obtained by conventional direct exposure.

In the above digital image processing,
A variety of input and output media can be used, but each of these media has its own color space, so the input data is properly converted to exactly match the color space of the output device. And expressed as a complex nonlinear relationship. For this conversion, a conversion method using a three-dimensional lookup table (3DLUT) is widely used.

Meanwhile, silver halide photographs are designed with characteristics such as gradation, spectral sensitivity, and multilayer effect for reproducing colors that are desirable for humans. This is a great feature of silver halide photography and one of the goals of various other image media. For example, in a multi-band camera or a DSC (digital still camera), it is possible to output a silver halide photographic image to some extent through a conversion process such as the 3DLUT.

[0007]

However, the above-mentioned 3)
In the image conversion by the DLUT, various characteristics included in the photographic light-sensitive material are mixed. For example, more detailed image processing such as color saturation enhancement of a specific color is performed in a silver halide photographic tone. Had a problem that it was inconvenient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and performs a photographic material-like image processing with high accuracy and performs a more detailed change process such as increasing or decreasing the saturation of a specific color. It is an object of the present invention to provide an image processing method and apparatus capable of easily obtaining a photo-like image by executing an incorporated image processing process, and a recording medium recording a program for executing the method.

[0009]

In order to solve the above problems, a first aspect of the present invention provides a method for input image data,
An image processing method for performing digital image processing and converting the image data into output image data for outputting as a photographic material-like image, wherein the image conversion process approximates image conversion by a 3DLUT that associates input image data with output image data. The present invention provides an image processing method characterized in that a photographic material-like image is obtained by using the image processing method.

Preferably, the image conversion process that approximates the image conversion by the 3DLUT includes a 1DLUT conversion in which at least two stages are combined.

Preferably, the image conversion process that approximates the image conversion by the 3DLUT includes at least a matrix conversion, and the saturation of a specific color can be changed by changing a coefficient of the matrix.

It is preferable that the matrix expresses a function equivalent to the layering effect of the photographic light-sensitive material.

In the image conversion process for approximating the image conversion by the 3DLUT, the logarithmic exposure obtained from the input image data is converted into a silver density value using a 1DLUT, and the silver density value is converted into an image. It is preferable that the data is converted into an image density value again by a 1DLUT after applying a matrix for changing the saturation of.

[0014] Similarly, in order to solve the above problems,
A second aspect of the present invention is an image processing apparatus that performs digital image processing on input image data and converts the input image data into output image data for outputting as a photographic material-like image. Correlate output image data 3
Provided is an image processing apparatus having image conversion means for performing image conversion that approximates image conversion by a DLUT and obtaining an image like a photographic material.

It is preferable that the image conversion means for performing image conversion that approximates the image conversion by the 3DLUT includes 1DLUT conversion means in which at least two stages are combined.

The image conversion means for performing an image conversion that approximates the image conversion by the 3DLUT includes at least a matrix conversion means, and the saturation of a specific color can be changed by changing a coefficient of the matrix. Is preferred.

It is preferable that the matrix expresses a function equivalent to the layering effect of the photographic material.

The image conversion means for performing an image conversion approximating the image conversion by the 3DLUT converts the logarithmic exposure amount obtained from the input image data into a silver density value.
It is preferable to include a UT conversion unit, a matrix conversion unit that changes the saturation of an image with respect to the silver density value, and a 1DLUT conversion unit that converts data converted by the matrix into an image density value.

Similarly, in order to solve the above problems,
According to a third aspect of the present invention, there is provided a computer-readable recording medium in which the image processing method is recorded as a program for causing a computer to execute the method.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing method and apparatus according to the present invention and a recording medium storing a program for executing the method will be described in detail based on preferred embodiments shown in the accompanying drawings. I do.

FIG. 1 is a block diagram schematically showing an image processing apparatus according to one embodiment of the present invention. Image processing device 1
0 is an image input means 12 such as a multi-band camera or a digital still camera (DSC) for taking a multi-band image, an image output means 14 such as a laser printer, and a display for displaying an image after image processing for confirmation. 1
An operation system 18 for the operator to give various instructions to the image processing apparatus 6 and the image processing apparatus 10 is connected.

The image processing apparatus 10 includes a conversion data converter 20 for performing predetermined data conversion on input image data, an exposure density calculator 22 for calculating an exposure density from the input image data, and a logarithm for converting the exposure density into a logarithmic exposure amount. An exposure amount calculator 24,
A 1DLUT 26 for converting the logarithmic exposure amount to a silver density value, a matrix conversion unit 28 for increasing the saturation of an image, and a 1DLUT 30 for converting the converted image data to an image density value.
Contains.

FIG. 2 shows an outline of the present embodiment. In the present embodiment, as shown in FIG. 2, an SPI image photographed by a multi-band camera or an image photographed by DSC is input, and the exposure density calculator 22 controls the spectral sensitivity of the photographic material and the spectral power of the photographing light source. Exposure density is calculated using the distribution, and this is calculated by the logarithmic exposure amount calculation unit 24, for example, by 1D.
Using a LUT to convert to laser exposure (log exposure)
On the other hand, the 1DLUT 26, the matrix conversion unit 28, and the 1DLUT 30 perform image processing in which the matrix and the 1DLUT are combined, and finally convert the image into a density value and output the density value.

Here, the image processing in which a matrix and a 1DLUT are combined to obtain a density value from a laser light amount is a part where image conversion is conventionally performed by a 3DLUT.
The point of approximation (replacement) by image processing combining T is an essential part of the present invention. This matrix and 1D
FIG. 3 shows details of the image processing combining the LUTs. As shown in FIG. 3, the laser light amount is converted into a silver density value by the 1DLUT 26, the matrix conversion is performed on the silver density value to increase the saturation, and the result is added to the laser light amount to obtain 1DLU.
At T30, the image is converted into an image density value, which is output as a density value. At this time, by changing the parameters of the matrix that approximates the conversion by the 3DLUT, the saturation of the specific color can be increased / decreased, and highly accurate image processing can be performed.

Hereinafter, referring to the flowchart of FIG.
The operation of the present embodiment will be described. First, in step 100, a subject is photographed by, for example, a multi-band camera as the image input unit 12, and photographed image data is input to the image processing apparatus 10. The multi-band camera includes a spectral filter and a CCD camera. The spectral filter may be an optical filter, but is preferably a liquid crystal tunable filter that is a wavelength tunable filter that can be easily controlled so as to transmit reflected light from a subject in a wavelength region set for each of a plurality of channels. . For example, using such a liquid crystal tunable filter, a photographing wavelength region is divided into a plurality of channels, for example, but not particularly limited to, for example, 16 channels. Shoot by. The photographed multi-band image is input to the image processing device 10 and the data conversion unit 20
An image signal obtained by receiving light by the CCD camera is A / D converted to a digital image signal, and other conversion such as DC offset correction is performed as necessary.

Next, in step 110, the exposure density calculator 22 calculates an exposure density value from the input digital image signal. In the exposure density calculator 22,
Using the reflectance data Rik (λ) of the subject, the spectral sensitivity Sk (λ) of the photographic material, and the spectral distribution L (λ) of the light source, the exposure density value EDik is calculated by the following equation (1). Here, λ represents a wavelength, i represents each pixel, k = B,
G and R. EDik = −Log [{Rik (λ) Sk (λ) L (λ) dλ} / {Sk (λ) L (λ) dλ}] (1)

Next, at step 120, the logarithmic exposure amount calculating section 24 calculates the exposure density value EDik by, for example, 1 DLU.
Using T, for each pixel i, for each color k = B, G, R, the logarithmic exposure amount (laser light amount) L0 = (LogB0i, L
ogG0i, LogR0i). The 1DLUT indicating the relationship between the exposure density value and the logarithmic exposure amount is created in advance by photographing, for example, a chart with a known reflectance.

Next, at step 130, the log exposure amount L0 is changed to the silver density value Ag = (AgBi, AgG) by the 1DLUT 26 showing the relationship between the log exposure amount of the photosensitive material and the silver density.
i, AgRi). Next, in step 140, the matrix conversion unit 28 causes the silver density value A
The color conversion is performed by multiplying g by a color conversion matrix M as in the following equation (2). AgM = MAg (2)

The coefficients (parameters) of the color conversion matrix M are determined according to the content of the saturation up (or down) of the image. For example, a plurality of points whose saturation is to be increased are selected from the image, and which color and how much the saturation is increased is determined. For example, when the saturation of R is increased at a certain point, the parameters of the matrix M are determined as shown in FIG. In FIG. 5, in symbols such as B → G, the left side (B) of → indicates the side that gives the multilayer effect, and the right side (G) of → indicates the side that receives the multilayer effect. The parameters in the shaded areas in the figure are
This represents a parameter to be changed when increasing the saturation of R. Further, it is assumed that R → R of the (3, 3) component at the lower right is changed so that the sum of the row components of the matrix M does not change. That is, when the matrix M is M = (mij) and i, j = 1, 2, 3, the row component is unchanged if mi1 + mi2 + mi3 = invariant.
This condition is for preventing the color balance of gray from being lost. Under this condition, the saturation of the image can be increased by arbitrarily changing the parameters.

For example, it is assumed that the matrix MA is given by the following equation (3).

(Equation 1) At this time, consider a case where the saturation of R is increased. As shown in FIG. 5, in this case, the components (3, 1) and (3, 1)
2) The component is changed, and the (3, 3) component is also changed so that the sum of the third row remains unchanged.

Therefore, for example, MA is changed as shown in the following equation (4) to obtain MB.

(Equation 2) Thus, the saturation increase component of B → R of (3,1) of MA is increased by +0.03 to −0.0250, and the saturation increase component of G → R of (3,2) is increased. Component-0.0
900 was increased by +0.02 to -0.0700 to increase the saturation of R. Further, the (3, 3) component is reduced by 0.13 + 0.02 = 0.05 from 0.1450 so that the sum of the third row is invariable, and 0.13
450-0.05 = 0.0950. The parameter may be changed by displaying the image conversion result on the display 16 and checking the result while the operator inputs the parameter from the operation system 18 to change the parameter.

Next, at step 150, the data AgM after the matrix conversion of the above equation (2) is added to the log exposure amount L0 to obtain L0M = L0 + AgM. concentration)
Convert to DC. Finally, in step 160, the density data is output to an image
Output from

FIG. 6 shows an image output result. This is obtained by converting the reproduced color into L * a * b * values and plotting them on an L * a * b * chromaticity diagram. Here, the arrow in the figure →
Is the reproduction result when the conversion by the matrix MA is used, and the point of the arrow → is the reproduction result when the conversion by the matrix MB is used. For example, in the red area inside the first quadrant of the figure, it can be seen that the arrow → moves in the direction away from the origin. This confirms that the saturation of R is moving in a higher direction. in this way,
According to the present embodiment, since the 3DLUT is expressed as a combination of the 1DLUT and the matrix conversion, the saturation of a specific color can be easily increased (or decreased) by changing the parameters of the color conversion matrix. As a result, A photo-like material-like image can be easily obtained.

Further, an image processing algorithm for causing a computer to execute the above-described image processing method is programmed, and is recorded on a computer-readable recording medium. By reading and using it, it becomes possible to execute desired image processing with an arbitrary device.

Although the image processing method and apparatus of the present invention and the recording medium on which the program for executing the method is recorded have been described in detail, the present invention is not limited to the above examples. Of course, various improvements and changes may be made without departing from the scope of the invention.

[0036]

As described above, according to the present invention, 3
By using an image processing process that approximates the conversion by the DLUT, it becomes possible to obtain a photographic material-like image. In particular, when the 3DLUT conversion is expressed as a combination of the 1DLUT and the matrix conversion, the saturation of a specific color can be easily increased (or decreased) by changing the parameters of the color conversion matrix. As a result, it becomes possible to easily obtain a photographic material-like image.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an outline of the present embodiment.

FIG. 3 illustrates a matrix and a 1DLUT according to the present embodiment.
FIG. 9 is an explanatory diagram schematically showing image processing combining.

FIG. 4 is a flowchart showing the operation of the present embodiment.

FIG. 5 is an explanatory diagram illustrating an example of a color conversion matrix according to the present embodiment.

FIG. 6 is a chromaticity diagram showing the result of increasing the saturation in the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Image processing apparatus 12 Image input means 14 Image output means 16 Display 18 Operation system 20 Data conversion part 22 Exposure density calculation part 24 Log exposure calculation part 26 1DLUT 28 which converts log exposure into silver density value 30 Matrix conversion part 30 1D for converting converted image data into image density values
LUT

Claims (11)

[Claims] 1. An image processing method for performing digital image processing on input image data and converting the input image data into output image data for outputting as a photographic material-like image, comprising: 3DLU to associate
An image processing method characterized in that an image-like material-like image is obtained by using an image conversion process that approximates image conversion by T. 2. The image conversion process that approximates the image conversion by the 3DLUT is performed by combining at least two stages.
The image processing method according to claim 1, further comprising a DLUT conversion. 3. The image conversion process that approximates the image conversion by the 3DLUT includes at least a matrix conversion, and the saturation of a specific color can be changed by changing a coefficient of the matrix. The image processing method according to 1. 4. The image processing method according to claim 3, wherein said matrix expresses a function equivalent to an overlay effect of a photographic material. 5. An image conversion process for approximating image conversion by the 3DLUT, wherein the logarithmic exposure obtained from the input image data is converted into a silver density value using a 1DLUT, and the silver density value is converted into an image. The image processing method according to any one of claims 1 to 4, wherein the data is converted into an image density value again by a 1DLUT after applying a matrix for changing the saturation of the image data. 6. An image processing apparatus for performing digital image processing on input image data and converting the input image data into output image data for outputting as a photographic material-like image, comprising: 3DLU to associate
An image processing apparatus, comprising: an image conversion unit that performs image conversion that approximates image conversion by T, and obtains an image like a photographic material. 7. The image processing apparatus according to claim 6, wherein the image conversion means for performing the image conversion that approximates the image conversion by the 3DLUT includes at least two-stage combined 1DLUT conversion means. 8. An image conversion means for performing an image conversion that approximates the image conversion by the 3DLUT includes at least a matrix conversion means, and can change the saturation of a specific color by changing a coefficient of the matrix. The image processing device according to claim 6. 9. An image processing apparatus according to claim 8, wherein said matrix expresses a function equivalent to an overlay effect of a photographic light-sensitive material. 10. An image conversion means for performing an image conversion approximating the image conversion by the 3DLUT, wherein the logarithmic exposure obtained from the input image data is converted into a silver density value.
Conversion means, matrix conversion means for changing the saturation of an image with respect to the silver density value, 1DLUT conversion means for converting data converted by the matrix into an image density value,
The image processing device according to claim 6, further comprising: 11. A computer-readable recording medium which records the image processing method according to claim 1 as a program for causing a computer to execute the image processing method.