JP2002016935A - Method and apparatus for converting color image data under different light sources as well as medium for recording program for converting color image data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert image data obtained by photographing under one light source (photographing light source) into image data possibly obtained under another light source (reference light source). SOLUTION: A color plate in which color pallets of a plurality of different colors are arranged is prepared. Reference image data of the plate under the reference light source is formed. Photographing image data and object image data of the plate are obtained by photographing the plate and an object. A conversion equation of a color space from the photographing color space to a reference color space is obtained by using reference image data and photographing image data of the plate. The object image data is converted into image data possibly obtained under the reference light source by using the equation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image data of an object photographed under a light source different from a light source to be referenced (or standard), such as a different external light condition, which can be obtained under a reference light source. The present invention relates to a method and apparatus for converting or simulating an image, and a medium storing a computer program for converting image data.

[0002]

2. Description of the Related Art The same object can be obtained by imaging due to imaging conditions, especially due to differences in light sources (not only specific equipment that emits light, but also different weather conditions such as sunny, cloudy, and rainy weather). The image has a very different tint.
For this reason, there are various problems.

[0003] For example, when flowers are cultivated on farms in various locations with different weather conditions and the digital camera images photographed by the farmer under the photographing conditions at that time are transmitted immediately after flowering, when the images are taken at the time of photographing each image, Since the color of the flower varies depending on the photographing conditions such as light environment and camera performance, it is not possible to obtain a colorimeter value in the standard colorimetric space. In addition, if it is possible to predict the color of clothes displayed or advertised under various external light environments, it is effective for cost reduction or sales promotion. For example, you can see how clothes displayed in an indoor environment look under external light. Further, in remote medical treatment, the color of a transmitted patient's complexion or a digital image of an affected part differs from that seen by the naked eye, which may hinder the determination.

[0004]

DISCLOSURE OF THE INVENTION The present invention captures image data obtained by photographing (including colorimetry) an object under one light source (called a photographing light source) with another light source (referred to as a reference light source). And a method for simulating image data that would be obtained under a reference light source, and a program for causing a computer to execute the processing. The purpose is to provide a medium.

Another object of the present invention is to provide a computer excellent in user operability, an operation method thereof, and a recording medium for controlling the computer.

In the method of the present invention, a color plate on which a plurality of color palettes of different colors are arranged is used. Preferably, the colors of the color palette are evenly selected in the color space to represent as much of the color space as possible. It is preferable that the number of color pallets is determined so that an error in image data conversion described later is minimized.

In the method of the present invention, first, reference image data of a color plate under a reference light source is created.
The reference light source is most commonly a standard light source, but may be any light source depending on the application. A shooting light source described later can be used as a reference light source for other image data conversion. There are various modes for creating reference image data.
Most typically, image data obtained by actually photographing (colorimetrically) a color plate under a reference light source is used as reference image data. Image data (L ^* , a ^* , b ^* ,
If the values of X, Y, Z, Y, x, y, R, G, and B are known (or can be predicted), the values can be adopted as reference image data. For example, the value is registered in a computer as reference image data. In such a case, the reference light source is a fictitious one that does not exist. The reference light source includes a light source that does not actually exist.

Next, according to the present invention, by photographing the same color plate and object under the photographing light source,
The image data of the color plate and the target image data of the target object are obtained. Most preferably, a digital camera will be used for shooting. Image data obtained by shooting at a remote place may be transmitted through a communication line. The photographing light source may be not only an artificial light source such as various illumination lamps but also sunlight. In the case of sunlight, the light varies depending on the weather, time, and the like, so that they may be considered as different imaging light sources.

According to the method of the present invention, a conversion formula of a color space from a photographing color space to a reference color space is obtained using the reference image data of the color plate and the photographed image data, and the color space conversion formula is obtained. The target image data is converted into image data that would be obtained under a reference light source. This conversion can be said to be conversion from the photographing color space to the reference color space. The calculation of the color space conversion formula and the conversion of the image data will most commonly be performed by a computer.

As described above, according to the present invention, image data obtained by photographing under one light source (photographing light source) is converted into image data that would be obtained under another light source (reference light source). Can be converted (simulated). Therefore, in various cases as described in the background art,
The hue under a desired light source can be predicted.

In a preferred embodiment, the reference image data and the photographed image data of the color plate are represented by an L ^* a ^* b ^* color system, and a lightness index L ^* and a perceived chromaticity index a
For each of ^* and b ^* , a color space conversion formula from the photographing color space to the reference color space is obtained, and for each of the lightness index L ^* and the perceived chromaticity indexes a ^* and b ^* , the above color space conversion formula is used. The target image data is converted into image data that would be obtained under a reference light source.

When image data in the L ^* a ^* b ^* color system is used, a color space conversion equation can be expressed by a linear function, and handling or processing becomes easy or simple.

In a further preferred embodiment, the lightness index L
^{For each of *} and the perceived chromaticity indices a ^* and b ^* , the range is divided into a plurality of sections, and a linear approximation equation is obtained for each section to obtain a color space conversion equation. Since the range in which the image data exists is divided into a plurality of sections and the color space conversion formula is obtained for each section, errors can be reduced.

In an embodiment in which image data conversion is performed using a computer system, a point defined by reference image data representing each color palette and photographed image data is drawn on rectangular coordinates for each color palette on a display screen. A graph represented by the obtained conversion formula is drawn and displayed. The user can visually recognize what conversion is being performed.

The program for operating the computer as described above can be defined as follows.

In other words, the program comprises a reference image data obtained under a reference light source of a color plate on which a plurality of color palettes of different colors are arranged, and a color image obtained by photographing the color plate under a photographing light source. A color space conversion formula from the photographing color space to the reference color space is determined using the photographed image data of the plate, and a point determined by the reference image data representing each color palette and the photographed image data is determined on the display screen. The target image data obtained by shooting the object under the shooting light source is drawn by displaying on a rectangular coordinate for each and drawing and displaying a graph represented by the obtained conversion formula.
Using the above color space conversion formula, the computer is controlled so as to convert to image data that would be obtained under a reference light source. The present invention provides a medium recording such a program.

When the L ^* a ^* b ^* color system is used, each color palette is represented on the display screen of the display device for each of the lightness index L ^* and the perceived chromaticity indexes a ^* and b ^*. A point determined by the reference image data and the captured image data is drawn on rectangular coordinates for each color palette, and a graph represented by the obtained conversion formula is drawn and displayed.

In another embodiment using a computer,
The color represented by the reference image data of the color plate is displayed on the display device by being classified for each color palette. The user can know the color of the color plate under the reference light source.

In a further preferred aspect, each of the color represented by the reference image data of the color palette and the color represented by the photographed image data is divided for each color pallet, and is represented by the color represented by the reference image data and the photographed image data. Is displayed on the display device in a form in which the colors to be compared are compared. The user can see and compare the color of the color plate under the reference light source with the color of the color plate under the photographing light source.

As described above, the program for controlling the computer includes a reference image data obtained under a reference light source of a color plate in which a plurality of color palettes of different colors are arranged, and a photographing of the color plate under a photographing light source. Using the obtained captured image data of the color plate, the color represented by the reference image data of the color palette and the color represented by the captured image data are each divided into color palettes and represented by the reference image data. The color and the color represented by the photographed image data are displayed on the display device in a contrasting manner, and the color space is converted from the photographed color space into the reference color space using the reference image data and the photographed image data of the color plate. Obtained by calculating the formula and shooting the object under the shooting light source Elephants image data, and controls the computer to use the color space conversion formula, and converts the image data that would be obtained under the reference light source. The present invention also provides a medium recording such a program.

A more preferred embodiment uses a color palette in which the color palettes are arranged in a plurality of columns and a plurality of rows.
Using a computer, the color represented by the reference image data of the color palette and the color represented by the photographed image data are arranged in a plurality of columns and rows, and the columns or rows of the color represented by the reference image data and the photographed image data Are alternately arranged and displayed in columns or rows of the color represented by. It is possible to better compare the color shade of the color palette under the reference light source with the color shade of the color palette under the photographing light source.

In another embodiment, a target image represented by target image data representing an object is displayed on a display screen using a computer system, and the image represented by the target image data converted by the above conversion formula is displayed. Display on the display screen. The user can visually recognize the color of the target image before and after the conversion.

In still another embodiment, a target image represented by target image data representing a target object is displayed on a display screen, and target image data included in a specified area in the displayed target image is converted by a conversion formula. Convert.
The user can specify a desired range and perform conversion.
If the specified range is small, the processing time can be reduced.

In still another embodiment, a target image represented by target image data representing a target object is displayed on a display screen, and image data of a designated pixel on the displayed target image is displayed. The user can know the image data of the desired pixel on the target image.

More preferably, color chart image data including image data of a number of known colors is prepared in advance. For example, input to a computer. In response to input of a search condition including at least a condition for color difference, image data satisfying the search condition with respect to the image data of the specified pixel is searched in the color chart image data, and a search result is displayed. The user can confirm which color on the color chart the image data of the designated pixel resembles by a numerical value (color difference).

In one embodiment, the search result is displayed by data including the color represented by the image data found by the search, the name thereof, and the color difference.

The image data conversion apparatus according to the present invention comprises: a first input means for inputting reference image data obtained under a reference light source of a color plate in which a plurality of color palettes of different colors are arranged; A second input unit for the photographed image data of the color plate and the target image data obtained by photographing the target object, and from the photographed color space to the reference color space using the reference image data of the color plate and the photographed image data. First means for obtaining a color space conversion equation, and second means for converting the target image data into image data that would be obtained under a reference light source using the color space conversion equation.

The first input means includes a device for inputting image data from a digital camera or a recording medium, a device for inputting numerical data, a device for receiving image data by communication, and the like. The second input means may include a device for capturing image data from a digital camera or a recording medium, a device for receiving image data by communication, and the like.

The present invention further provides a computer device on which the above-mentioned program is installed.

[0030]

FIG. 1 is a block diagram showing a configuration of an apparatus for simulating a color change of a target image due to a difference in light source (color conversion of digital image data).

This simulation device is realized by a computer system. Computer system includes computer 10, program memory 11, storage device (database) 12, display device (CRT or LCD)
13, an input device 14 including a mouse and a keyboard, an FD drive 15, a CD-ROM drive 16, an MO drive 17, a digital camera interface 18, and a memory card interface 19.

The program memory 11 stores a program for executing a color change simulation and other processes which will be described in detail later, and is usually realized by a hard disk device or a semiconductor memory.

The storage device 12 is also realized by a hard disk device or a semiconductor memory. The storage device 12 stores data necessary for color change simulation and other processing, and includes an area 12A for storing reference image data of a color plate and an area 12 for storing display color conversion data.
B, an area 12C for storing color chart image data (RHS), an area 12D for storing color chart image data (JHS), and an area 12 for storing user image data
E.

The color chart image data includes, for a plurality of known (or specific or defined) colors, a color identification symbol (including a color name and a color name) and image data representing the color, respectively. These are the corresponding files (files), specifically RHS (Royal Horticultural Society: Th
e Royal Horticultural Society) issued color chart and JHS
("Japanese Gardening Plant Standard Color Chart" published by Japan Color Research Institute). The color chart is also called a color chart, a color chart card, and a color scheme card.

A color plate is used for simulating a color change. The color plate is a plate-like body (including a sheet) (one sheet may be divided into a plurality of sheets if the number of colors is large), and a plurality of colors are displayed at different places. In short, the surface of one sheet is divided into a plurality of regions (for example, divided into a plurality of regions in a vertical direction and a horizontal direction), and each region represents a different color. A different color is represented by painting a different color on each area of the plate-like body or pasting a colored sheet. The color plate is preferably durable. Also consider the reflection of light (for example, avoid reflections like mirrors). It is preferable to select the number of colors within a range in which a simulation with as few errors as possible can be performed. If the number of colors is small or too large, an error is likely to occur. Specifically, several tens of colors (for example, 60 colors) are preferable. These colors are evenly chosen to represent all colors in the color space as much as possible. The area where different colors are represented is called a palette. It can be said that the color plate has a plurality of different color palettes.

The reference image data of the color plate stored in the area 12A is color image data for each pallet of the color plate obtained by measuring (photographing) the color plate under the reference light source. Although color image data is represented by various color systems, in this embodiment, reference image data of a color plate is represented by an L ^* a ^* b ^* color system (L ^* is a lightness index, a ^* , b ^* is the perceived chromaticity index). Therefore, in this area 12A, the reference image data name (file name), the number of palettes of the color plate, the color name and the L ^* , a
^* , B ^* values are stored. The color name is a name representing a color of a color palette. This color name can be freely assigned, or if the color chart (RHS, J
When the colors included in HS) are used for the color palette, the color identification symbol of the color chart can be used as the color name. A plurality of reference image data (files) may exist. For example, when different reference light sources are used, a plurality of reference image data are obtained. The reference image data name (file name) is for identifying these plurality of reference image data.

Most commonly, the reference image data of the color plate is image data obtained by actually measuring the color plate (including photographing with a digital camera or the like) under a reference light source. Any light source (including sunlight) may be used as the reference light source. Most typically, the reference light source is a standard light source C (a light source that emits light having a relative color temperature of 6774K). The captured image data of the color plate included in the user image data described later can also be used as the reference image data of the color plate. In this case, the reference light source is a light source used in photographing when the photographed image data is obtained. Although image data is strongly affected by the light source, the effect of the difference in the type of digital camera used for shooting is small. Reference light sources include fictitious light sources that do not actually exist. For example, the reference image data of the color plate is artificially created (or, for example, using the image data of the color chart described above, which is predetermined according to the color palette).
The information may be input to the computer 10 and stored in the area 12A. Including all these aspects, "reference image data of a color plate obtained by measuring the color plate under a reference light source" or "reference image data of a color plate created under a reference light source" .

The display device 13, for example, a CRT display device,
The display colors may differ from one another, and the display colors may change due to aging or the like. Even one image data may be displayed in different colors depending on the display device or at different times. Display conversion data in which data for correcting a display color in such a display device is stored in the area 12B (L ^* a ^* b ^* / expression for RGB conversion)
It is. L representing a specific color, for example, red, green, blue, and white (IDs indicate these)
^* , A ^* , b ^* values (indexes based on international standards) and image data Y, x, y for correctly displaying their colors on a display device are stored. Image data conversion is performed by interpolation for colors other than the above four colors. The expression for the conversion may be realized by a table or the like. The conversion from L ^* a ^* b ^* to RGB when displaying on the display device is performed when the color specified on the screen of the display device is captured.
Is converted to L ^* a ^* b ^* .

The image data Y, x, y are values in the XYZ color system. That is, in the XYZ color system, the stimulus value X,
Y and Z are used, and the chromaticity x and y are values obtained by standardizing the stimulus values X and Y by X + Y + Z. The RGB color system and the XYZ color system can be mutually converted by a linear expression.

In the area 12C, in the color chart image data (RHS), color identification symbols, group names, L ^* , a ^* , b ^* values in the L ^* a ^* b ^* color system in the color chart. , R, G, B in the RGB color system
Values, hue H in the Munsell color system, lightness V, chroma C, lightness index L in the Hunter uniform perceived color space, perceived chromaticity index a, b, and stimulus value Y and chromaticity x, y in the XYZ color system. Is stored. The group name (color system name) indicates a color system when the colors are divided into color systems such as red, yellow, and pink so that the user can intuitively understand each color of the color chart ( Symbol). A color chart image (J
HS) stores the same data.

In the area 12E, image data of a color plate photographed by the user (referred to as color plate photographed image data) and image data of the object photographed by the user (referred to as target image data) are stored in association with each other. ing. A file name specifies a pair of captured image data of a color plate and target image data.

A user can use a light source (photographing light source such as sunlight, indoor light, strobe light, etc.) available at a place (site) where an object is placed or present (site).
, An object is photographed using a digital camera (or a colorimeter). In some cases, both the target object and the color plate are included in the field of view and photographed at the same time, or in other cases, photographed separately under the same photographing light source. In any case, the photographed image data of the color plate and the target image data obtained by photographing are stored in the area 12E in association with each other (for example, in one file).

Each of these image data is represented by L ^*
a ^* b ^* L ^* in the color system, a ^*, b ^* values, R in the RGB color system, G, B values, H in the Munsell color system, V, C value, the brightness in the Hunter uniform perceptual color space index L, the perceived chromaticity index a, b, and one or more of the stimulus value Y and the chromaticity x, y in the XYZ color system. The mutual conversion between these color systems can be performed by a known method.

As will be described in detail later, the display device 13 includes a color plate reference image, a color plate photographed image, a target image, a color space conversion graph, various numerical values, a mode for proceeding with processing, buttons and the like. Is displayed.

The input device 14 is used to execute an instruction (mouse click) for proceeding with the processing in accordance with the display on the display device 13, to designate a place on the display screen with a mouse, to input a data value such as reference image data, and the like. Things.

The FD drive 15 reads data from the FD and writes data to the FD. For example, when reference image data, color chart image data, user image data, and the like are stored in the FD, the FD drive 15
Reads these image data from the FD. The read image data is stored in the corresponding area (12A, 12C, 12D, 12E, etc.) of the storage device 12 by the computer 10.

The CR-ROM drive 16 reads data from a CD-ROM. For example, a program for simulation of color conversion and the like is stored in the CD-ROM. This program is read from the CD-ROM by the drive 16 and stored in the program memory 11. The MO drive 17 is used when image data and programs are stored on an MO (magneto-optical or magneto-optical) disk instead of an FD or CD-ROM.

As described above, the color plate may be photographed using a digital camera under a reference light source.
The color plate and the object are photographed under a photographing light source using a digital camera. These image data obtained by the digital camera are transferred from the digital camera to the computer 10 through the digital camera interface 18 and stored in the corresponding area (12A or 12E) in the storage device 12.

When image data obtained by the digital camera is stored in a memory card, the memory card is connected to the memory card interface 19. Image data is read from the memory card by the computer 10 through the interface 19, and is stored in the storage device.
Stored in 12 corresponding areas.

Further, a program for communication (including Internet communication) with a communication device including the MODEM is provided in the computer 10 of the simulation device as needed. User image data transmitted through a public line, a dedicated line, or the Internet is stored in an area 12E of the storage device 12.

FIG. 2 shows an example of a reference image of a color plate and a photographed image of the color plate. The color plate has a total of 15 pallets in 5 rows and 3 columns. The colors of these color palettes are respectively represented by C1 to C15 (Cn: n
= 1 to 15).

In the reference image, color image data obtained by photographing (including colorimetry) the colors C1 to C15 of the color palette of the color plate under the reference light source are respectively C1,1 to C15,1 (Cn, 1). Similarly, the color C1 of the color palette of the same color plate
Image data obtained by photographing (including colorimetry) images under the photographing light source are C1,2 to C15,2 (Cn,
2). Since each color palette represents a uniform color, it shall be represented by one image data. (If the color palette has color unevenness, the average value of the image data of the pixels representing the color palette should be used.) Just fine).

There is a difference between the reference image data Cn, 1 under the reference light source and the photographed image data Cn, 2 under the photographing light source based on the difference in light source. It is expected that these differences will generally be represented by very complex functions in all visible color ranges (the color ranges of the color palette on the color plate).

However, according to the verification work performed by the inventors, the image data is represented by the L ^* a ^* b ^* color system, and the lightness index L ^* and the perceived chromaticity indexes a ^* and b ^* are expressed as: When the range of possible values is divided into a plurality of (preferably about 4 to 5) sections (sections), it can be seen that in each section, the relationship between the reference image data and the captured image data can be linearly approximated. Was.

FIG. 3 shows this state. In FIG. 3, (A) shows the lightness index L ^* , and (B) and (C) show the perceived chromaticity indexes a ^* and b ^* , respectively. In each of these graphs, the horizontal axis is the reference image. Data (L
^* , A ^* , and b ^* are represented by L1, a1, and b1, respectively, and the vertical axis represents captured image data (L ^* , a ^* , and b ^{* represent} L
2, a2, b2). In these graphs, points on the coordinates determined by the reference image data representing the colors C1 to C15 of the color palette on the color plate and the photographed image data are indicated by black circles.

The entire range (the range of L ^* , a ^* , b ^* ) on the horizontal axis is divided into four sections (the sections are preferably determined in advance). Least square approximation (1
The following is performed, and the resulting primary approximate straight line is shown (the primary approximate straight line is a polygonal line that can be broken at three points).

These first-order approximate straight lines convert a color space under a photographing light source (referred to as a photographing color space) into a color space under a reference light source (referred to as a reference color space). Therefore, target image data obtained by shooting under a shooting light source is represented by the L ^* a ^* b ^* color system shown in FIG.
The next approximation straight line can be converted into image data that would be obtained under the reference light source.

The simulation apparatus shown in FIG. 1 has several modes such as an image conversion mode and a color data search mode. These modes are selected by the user on the first appearing menu screen and during the processing of each mode as described later.

FIG. 4 shows a flow of processing according to a computer program in the image conversion mode.

It is assumed that the reference image data of the color plate has already been created and stored in the area 12A of the storage device 12. For example, a color plate is photographed using a digital camera under a reference light source or measured using a colorimeter, and image data (eg, RG
B) (represented by the FD drive 15), directly from the digital camera through the digital camera interface 18 or from the memory card through the memory card interface 19 Is read into L ^* a ^* b ^*
The data is converted into a color system and stored in the area 12A. Alternatively, the user inputs the reference image data from the keyboard of the input device 14. Instead, the user specifies the color of the color pallet from the color chart image data. These image data are stored in the area 12A as reference image data.

It is assumed that user image data is also stored in the area 12E. The user photographs the object and the color plate with a digital camera. The image data obtained thereby is taken into the computer 10 directly from the camera through the digital camera interface 18 or from a memory card removed from the digital camera through the memory card interface 19, and is stored in the L ^* a ^* b ^* color system. The data is converted into data and stored in the area 12E.

The user designates reference image data under a desired reference light source from among those stored in the reference image data area 12A (reference image data name designation). If only one type of reference image data is stored in the area 12A, there is no need to specify a data name.

Then, the computer 10 reads the designated reference image data from the area 12A of the storage device 12 and converts it into a format for display (L ^* a with reference to the display conversion data in the area 12B). ^* b ^* is converted to RGB) and displayed on the display screen of the display device 13 (step 2).
1).

Further, the user presses a "read user image data" button B8 (see FIG. 5), which will be described later, and designates a desired file name to be subjected to color conversion (simulation) in the user image data. Then, the designated user image data (the captured image data of the color plate and the target image data) is stored in the storage device (hard disk) 12.
Is read from the area 12E and displayed on the display device 13 (step 22). Pressing a button on the display screen means specifying the area of the button with the cursor and clicking the mouse.

FIG. 5 shows how the reference image data, the photographed image data, and the target image data are displayed.

On the display screen, a color plate display window W1 appears on the right half (slightly smaller than half), and a user image display window W2 appears on the left half (slightly larger than half).

In the upper half of the color pallet display window W1, there is a color plate area P, below which several buttons B5, B6, B7 appear.

In the color plate area P, a color palette for two color plates is displayed. The odd columns M1, M3, and M5 counting from the left are for reference images, and the even columns M
2, M4 and M6 are for photographed images. That is, the column M1
Shows a color pallet image represented by reference image data C1,1 to C5,1 and a column M3 shows reference image data C6,
The color palette image represented by 1 to C10,1 is
In column M5, color pallet images represented by reference image data C11,1 to C15,1 are displayed. Here, the color palette image does not need to be the same or similar in shape to the color palette of the color plate (in the case of a square, the aspect ratio is the same), and the same color as the color obtained by shooting under the reference light source is displayed. I just need to know. This is the same for captured images. In the color plate area P, the photographed image data C1,2 to C5,
2, a color palette image represented by photographed image data C6,2 to C10,2 in column M4, and photographed image data C11,2 in column M6.
The color palette images represented by .about.C15,2 respectively appear (see FIG. 6).

As described above, in the color plate area P, the color palette image represented by the reference image data and the color palette image represented by the photographed image data are displayed adjacent to each other in one row,
The user can easily compare the color under the reference light source with the color under the shooting light source. Images are not line-by-line, but one
It may be displayed adjacent to each line.

The "start plate position setting" button B5 is pressed when an area of a photographed image (color pallet image) I2 described below is designated by a cursor. The "create conversion data" button B6 is for instructing creation of data (conversion data) representing a straight line by the above-described linear approximation. The "conversion" button B7 is for instructing the start of image data conversion after designating a conversion area of the target image I1 described below.

In the user image display window W2,
A target image (indicated by reference numeral I1) represented by the target image data selected by the user and a captured image (color pallet image) (indicated by reference numeral I2) represented by the captured image data of the color plate are displayed. At this time, it goes without saying that the conversion data for display in the area 12B of the storage device 12 is used.

Below the window W2, four buttons B1, B2, B3, B4 appear. The “region designation start” button B1 is pressed when the region on the target image I1 where the color conversion (simulation) of the image data is desired to be designated using the cursor. The "shape" button B2 is for selecting the shape of the area to be specified. The “area clear” button B3 is pressed when the area specified on the target image I1 is canceled and the area is specified again (the area specification is started again using the button B1). The "search" button B4 is pressed when shifting to the color data search mode. Two buttons B8 and B9 also appear below the window W1. The “read user image data” button B8 is for instructing to start reading user image data from the area 12E of the storage device 12. The "end" button B9 is pressed to end all processing.

First, the user "starts plate position setting"
The button B5 is pressed, and the position of the color plate image I2 in the window W2 is designated by the cursor using the mouse. For example, the upper left corner of the upper left color palette image of the image I2 and the lower right corner of the lower right color palette image are designated by the cursor.

Then, the computer 10 takes in the image data in the rectangle defined by the two designated points (step 23). That is, the image data in the display memory is transferred to the memo work area. At this time, the storage device 12
The reverse conversion from the display image data to the original image data is performed using the display conversion data in the area 12B. Of course, the photographed image data in the user image data in the area 12E of the storage device 12 may be used. Color plate image I2
Is designated, the positions of the color pallets constituting the positions are known in advance, so that the computer can obtain the photographed image data of each color pallet.

As described above, the color plate area P of the window W1 is
The color palette of the color represented by the captured image data is displayed in the even-numbered columns (step 24) (see also FIG. 6).

When the user presses the "create conversion data" button B6, a first-order approximate line for color space conversion is calculated (step 25). As described above, using the values L ^* , a ^*, and b ^* of the reference image data and the photographed image data, for each value, the least squares linear approximation is performed for each of a plurality of divided sections for conversion. A linear equation representing a straight line is obtained.

The user can switch the display screen of the window W2 using the tags T1 and T2. FIG. 5 shows an “image” display screen (window) (“image” tag T
1). When the user selects the “conversion” tag T2 (designates the tag T2 with the cursor and clicks the mouse), the window W2 in the display screen of the display device 13 becomes the “conversion” display screen (see FIG. 6). (Window) (or graph display window) W3. In window W3,
The three graphs shown in FIG. 3 are displayed. This graph display allows the user to see the color space conversion formula.

In this window W3, the color names of the reference image data, the values of L ^* , a ^*, and b ^* (L1, a1, b
1), and L ^* , a ^*, and b ^{* of the} captured image data
(L2, a2, b2) are displayed. By looking at this list, the user can know how much the value of the reference image data differs from the value of the captured image data.

Subsequently, the user selects the "image" tag T1 and returns the window W1 to the one for displaying the user image (FIG. 7).
reference). Press the "area designation start" button B1 and click the "shape"
The shape of the designated area is selected with the button B2. In FIG. 7, a square is selected. By pressing the button B2, the character representing the shape changes like a hexagon or an octagon, so that the user can select any one of a plurality of shapes. Thereafter, the user specifies an area on the target image I1 where the color conversion is to be performed. For example, a representative point (for example, in the case of a quadrangle, two points at both ends of a diagonal line thereof) is designated by a cursor position and a mouse click. In FIG. 7, an area surrounded by a broken line is an area specified by the user. As described above, the user can designate the entire target image I1 or a part thereof. When a part is specified, the time required for the conversion can be reduced, and the user can roughly know how the color changes. The computer 10 acquires coordinates representing the designated area (step 26).

Thereafter, when the "Convert" button B7 is pressed by the user, the target image data in the previously designated area is photographed under the reference light source based on the created linear approximation formula. The image data is converted into image data of a color that can be obtained (step 27). The target image after the conversion is shown in FIG.
As shown by 11, in the window W2, the target image I1 is displayed in place of the target image I1.

If the user presses the "region designation start" button B1 (step 28), the process returns to step 26, where the user can again designate another region on the target image I1 and perform color conversion. The user can also press the "read user image data" button B8 (step 28), read another user image (file) from the area 12E of the storage device 12, and repeat the processing from step 22.

The user can also move to the color data search mode. In this case, the user designates an arbitrary point on the target image I1 displayed in the window W2 with the cursor and clicks the mouse. Further, the "search" button B4 is pressed (step 29).

When the user presses the "end" button B9, all the processes are completed.

FIG. 9 shows the processing in the color data search mode. In the color data search mode, the color of a point (pixel) specified by the user in the target image I1 (or I11) displayed in the window W2 is represented by a color chart (RHS).
Alternatively, it is checked which color is close to the color specified in JHS) and the result is output.

As described above, the user sets the target image I1
(Or I11) by specifying the desired point on the cursor
When the "search" button B4 is pressed, a search condition input screen is displayed as shown in FIG. 10 (step 31). In this display screen, a window W11 displays the L ^* value, a ^* value, and b ^* value of the pixel designated by the user, and also displays a box for inputting a color difference (ΔE). If the pixel specified by the user on the target image I1 or I11 is an image part before color conversion, L ^* , a ^* , b ^* before color conversion ^.
If the value is the image portion after color conversion, L ^* , a after color conversion
^* , B ^* values will be displayed.

The color difference ΔE is a color difference (geometric distance between two points in the color space) in the L ^* a ^* b ^* color space. The value (color difference) entered in this box determines the range of colors to be searched (maximum color difference). In Fig. 10, the color difference "13"
The following is entered.

The window W12 is used to specify a color chart to be searched, and one of RHS and JHS is specified. In the example of FIG. 10, JHS is specified. Window W13 indicates that the color data search is performed in the L ^* a ^* b ^* color system.

When the user inputs the above search conditions and presses the "OK" button B11 (step 32), the computer 10 returns the input search conditions, that is, the L ^* value displayed in the window W11. (75.7636) a ^* value (6.81
09), b ^* value (3.1253), color difference (ΔE) is 13 or less, and the color chart incorporates JHS, L ^* a ^* b ^* color system (step 33).

The computer 10 reads the specified color chart JHS from the area 12D of the storage device 12 into the work area of the memory (step 34), and in the image data of the color chart, specifies the specified L ^* , a ^* , b ^*. Find all image data with values and color differences of 13 or less (Step 3
Five).

The search results are displayed in ascending order of color difference as shown in FIG. On this display screen, the upper left corner shows that 10 image data were found as color data having a color difference of 13 or less as the number of searches (step 3).
6).

In the left half of the screen, a window W11 shown in FIG.
And the color of the image data of the designated pixel and L ^* , a
^* , B ^* values are displayed, and in the right half, the color data in the color chart JHS found by the search are displayed in ascending order of the color difference. The displayed items are color identification symbol, group name, color (displayed in that color), color difference ΔE,
L ^* , a ^* , b ^* values, and R, B, G values.

When the user presses the "return" button B14, the process returns to step 31 again (step 37). In FIG. 10, when the "cancel" button B12 is pressed in step 32, the process returns to the image conversion mode (FIG. 4). When the “print” button B13 is pressed in FIG. 11, the list in FIG. 11 is printed by the printer.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a color change simulation apparatus.

FIG. 2 shows an example of reference image data and photographed image data of a color plate.

FIGS. 3A, 3B, and 3C are graphs showing how an approximate straight line for color conversion is obtained.

FIG. 4 is a flowchart illustrating a processing procedure in an image conversion mode.

FIG. 5 shows a screen displaying a user image.

FIG. 6 is a screen showing a graph in which an approximate straight line for color conversion is obtained.

FIG. 7 shows a screen for designating an area of a target image to be color-converted.

FIG. 8 is a screen on which a target image after color conversion is displayed.

FIG. 9 is a flowchart illustrating a processing procedure in a color data search mode.

FIG. 10 shows a search condition input screen.

FIG. 11 shows a display screen of a search result.

[Explanation of symbols]

 10 Computer 11 Program memory 12 Storage device 12A Reference image data storage region 12B Display conversion data storage region 12C Color chart image data (RHS) storage region 12D Color chart image data (JHS) storage region 12E User image data storage region 13 Display device 14 Input device 15 FD drive 16 CD-ROM drive 17 MO drive 18 Digital camera interface 19 Memory card interface

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Okada 1-5-8 Shinmachi, Nishi-ku, Osaka, Osaka Prefecture Japan Research Institute, Limited (72) Inventor Yuko Fukui 1-1, Wakayamadai, Shimamotocho, Mishima-gun, Osaka Prefecture -1 Suntory, Ltd. Basic Research Laboratory (72) Inventor Yukihisa Katsumoto 1-1-1, Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka Prefecture F-term (Reference) 5B057 AA11 BA02 BA19 BA25 CA01 CA08 CA12 CB01 CB08 CB12 CC01 CE17 CE18 DA17 DB02 DB06 DB09 5C066 AA13 CA08 EB01 GA01 KE01 5C077 MM27 PP31 PP32 PP36 PP37 PP43 PQ08 PQ22 SS05 SS07 TT09 5C079 HB01 HB05 HB08 HB11 JA17 LB02 MA10 MA11 MA17 NA03

Claims (32)

[Claims] 1. A color plate in which a plurality of color palettes of different colors are arranged, reference image data of the color plate is prepared under a reference light source, and the color plate and an object are photographed under a photographing light source. To obtain the photographed image data and the target image data of the color plate, obtain the color space conversion formula from the photographed color space to the reference color space using the reference image data and the photographed image data of the color plate, A method of converting the target image data into image data that would be obtained under a reference light source using a spatial conversion formula. 2. The color plate reference image data and the photographed image data are represented by an L ^* a ^* b ^* color system, and the lightness index L ^* and the perceived chromaticity indices a ^* and b ^* are respectively referenced from the photographing color space. A color space conversion formula for the color space is obtained, and the target image data is obtained under the reference light source using the color space conversion formula for each of the lightness index L ^* and the perceived chromaticity indexes a ^* and b ^*. 2. The method of claim 1, wherein the method converts to wax image data. 3. A lightness index L ^* and a perceived chromaticity index a ^*.
3. The method according to claim 2, wherein for each of b and b ^* , the range is divided into a plurality of sections, and a linear approximation equation is determined for each section to obtain a color space conversion equation. 4. A method for performing image data conversion using a computer system, wherein a point defined by reference image data representing each color palette and photographed image data is displayed on a display screen in rectangular coordinates for each color palette. 4. The method according to claim 1, further comprising drawing and displaying a graph represented by the determined conversion formula. 5. A method of converting image data using a computer system, wherein each color palette is displayed on a display screen of a display device for each of a lightness index L ^* and a perceived chromaticity index a ^* and b ^*. 4. The method according to claim 2, wherein a point defined by the reference image data and the photographed image data is drawn on rectangular coordinates for each color palette, and a graph represented by the obtained conversion formula is drawn and displayed. 6. A method for converting image data using a computer system, wherein colors represented by reference image data on a color plate are displayed on a display device by being divided for each color palette. The method according to any one of the preceding claims. 7. The color represented by the reference image data of the color palette and the color represented by the photographed image data are classified into each color palette, and the color represented by the reference image data and the color represented by the photographed image data are separated. 7. The method according to claim 6, wherein the information is displayed on the display device in a contrasting manner. 8. A color palette in which a color palette is arranged in a plurality of columns and a plurality of rows, and a color represented by reference image data of the color palette and a color represented by a photographed image data are arranged in a plurality of columns and a plurality of rows.
8. The method according to claim 7, wherein columns and rows of colors represented by the reference image data and columns or rows of colors represented by the captured image data are alternately displayed. 9. A method for converting image data using a computer system, comprising: displaying a target image represented by target image data representing a target object on a display screen;
9. The method according to claim 1, wherein an image represented by the target image data converted by the conversion formula is displayed on a display screen. 10. A target image represented by target image data representing a target object is displayed on a display screen, and target image data included in a designated area in the displayed target image is converted by a conversion formula. 10. The method according to 9. 11. A method for converting image data using a computer system, comprising displaying a target image represented by target image data representing a target object on a display screen, and specifying a designated pixel on the displayed target image. The method according to any one of claims 1 to 10, wherein the image data is displayed. 12. Color chart image data including image data of a number of known colors is prepared in advance,
An image data that satisfies a search condition with respect to the image data of the specified pixel is searched in the color chart image data in response to input of a search condition including at least a condition regarding color difference, and a search result is displayed. 11
The method described in. 13. The method of claim 12, wherein displaying the search results includes displaying the color represented by the image data found by the search, its name, and a color difference. 14. A reference image data obtained under a reference light source of a color plate on which a plurality of color palettes of different colors are arranged, and a photographed image of the color plate obtained by photographing the color plate under a photographing light source A conversion formula of a color space from a photographing color space to a reference color space is obtained using the data, and a point determined by the reference image data representing each color palette and the photographed image data on the display screen is defined by rectangular coordinates for each color palette. The target image data obtained by imaging the object under the photographing light source is drawn under the reference light source using the above color space conversion formula. A medium on which a program for controlling a computer to convert the image data into the image data obtained in the above is recorded. 15. The program uses the reference image data and the photographed image data represented by the L ^* a ^* b ^* color system to calculate a lightness index L ^* and a perceived chromaticity index a ^* and b ^* , respectively. , A color space conversion formula from the photographing color space to the reference color space is obtained, and for each of the lightness index L ^* and the perceived chromaticity indexes a ^* and b ^*, a reference representing each color palette on the display screen of the display device. A point determined by the image data and the captured image data is drawn on rectangular coordinates for each color palette, and a graph represented by the obtained conversion formula is drawn and displayed. The lightness index L ^* and the perceived chromaticity indexes a ^* and b are displayed. ^* for each computer using the above color space conversion formula, the target image data, it will be obtained under the reference light source to convert the image data And controls, medium of claim 14. 16. The program according to claim 1, wherein the lightness index L ^* and the perceived chromaticity indexes a ^* and b ^* are:
16. The medium according to claim 15, wherein the computer controls the computer so that the range is divided into a plurality of sections, and a linear approximation equation is determined for each section to obtain a color space conversion equation. 17. The computer-readable storage medium according to claim 14, wherein said program controls a computer to display colors represented by reference image data of a color plate on a display device by dividing the colors by a color palette. The medium according to claim 1. 18. The program according to claim 18, wherein the program divides each of the color represented by the reference image data of the color pallet and the color represented by the photographed image data into each color pallet, and divides the color represented by the reference image data and the photographed image data. 18. The medium according to claim 17, wherein the medium controls a computer to display the color on the display device in a form in which the color is represented. 19. The program according to claim 1, wherein, for the color palette in which the color palette is arranged in a plurality of columns and a plurality of rows, each of the color represented by the reference image data of the color palette and the color represented by the photographed image data is arranged in a plurality of columns and a plurality of rows. 19. The computer according to claim 18, wherein the computer is arranged to arrange and display the columns or rows of the color represented by the reference image data and the columns or rows of the color represented by the captured image data alternately. Medium as described. 20. Reference image data obtained under a reference light source of a color plate on which a plurality of color palettes of different colors are arranged, and a photographed image of the color plate obtained by photographing the color plate under a photographing light source Using the data, the color represented by the reference image data of the color palette and the color represented by the photographed image data are divided for each color palette, and are represented by the color represented by the reference image data and the photographed image data. The image is displayed on a display device in a form in which colors are compared with each other, and a conversion formula of a color space from a photographing color space to a reference color space is obtained using the reference image data of the color plate and the photographed image data. Using the above color space conversion formula, target image data obtained by shooting the target object is A medium in which a program for controlling a computer to convert the image data into the image data that can be obtained under a reference light source is recorded. 21. The program according to claim 14, wherein, for the color palette in which the color palette is arranged in a plurality of columns and a plurality of rows, each of the color represented by the reference image data of the color palette and the color represented by the photographed image data is stored in a plurality of columns and a plurality of rows. 21. The computer according to claim 20, wherein the computer is arranged to arrange and display the columns or rows of the color represented by the reference image data and the columns or rows of the color represented by the captured image data alternately. The described medium. 22. The program uses a reference image data and a photographed image data of a color plate represented by an L ^* a ^* b ^* color system to generate a lightness index L ^* and a perceived chromaticity index a ^* and b. For each of ^* , the color space conversion formula from the photographing color space to the reference color space is obtained, and the lightness index L
^{For each of *} and the perceived chromaticity indices a ^* and b ^* , the computer is controlled so as to convert the target image data into image data that would be obtained under a reference light source using the above color space conversion formula. There is a claim
22. The medium according to 20 or 21. 23. The program according to claim 13, wherein the lightness index L ^* and the perceived chromaticity indices a ^* and b ^* are:
23. The medium according to claim 22, wherein the range is divided into a plurality of sections, and a computer is controlled so as to obtain a linear approximation equation for each section and use the obtained equation as a color space conversion equation. 24. The program according to claim 17, wherein the program displays a target image represented by target image data representing the target object on a display screen, and displays an image represented by the target image data converted by the conversion formula on a display screen. The medium according to any one of claims 14 to 23, which controls a computer. 25. The program displays a target image represented by target image data representing a target object on a display screen, and converts target image data included in a designated area in the displayed target image by a conversion formula. 25. The medium according to claim 24, which controls a computer to perform the operation. 26. The program controls a computer to display a target image represented by target image data representing a target object on a display screen and to display image data of a designated pixel on the displayed target image. 26. The medium according to any one of claims 13 to 25, wherein 27. The program, in response to input of a search condition including at least a condition for color difference, converts image data satisfying the search condition with respect to the image data of the specified pixel into a large number of known colors. 27. The medium according to claim 26, wherein the medium is for controlling a computer to search in color chart image data including image data and to display a search result. 28. The medium according to claim 27, wherein the display of the search result includes a display of a color represented by the image data found by the search, its name, and a color difference. 29. First input means of reference image data obtained under a reference light source of a color plate in which a plurality of color palettes of different colors are arranged, and photographing the color plate and an object under a photographing light source. Using a second input means of the obtained captured image data of the color plate and the target image data, and a reference image data of the color plate and the captured image data, a conversion formula of a color space from a captured color space to a reference color space is calculated. An apparatus comprising: a first means for determining; and a second means for converting the target image data into image data that would be obtained under a reference light source using the color space conversion formula. 30. A lightness index L ^* and a perceived chromaticity index a ^* and b ^* using a color plate reference image data and a photographed image data represented by an L ^* a ^* b ^* color system ^.
For each of the above, the first means for obtaining the color space conversion formula from the photographing color space to the reference color space, and for each of the lightness index L ^* and the perceived chromaticity indexes a ^* and b ^* , 30. The apparatus of claim 29, further comprising the second means for using the target image data to convert to image data that would be obtained under a reference light source. 31. Lightness index L ^* and perceived chromaticity index a
31. The apparatus according to claim 30, further comprising: the first unit that divides a range of each of ^* and b ^* into a plurality of sections and obtains a linear approximation equation for each section to obtain a color space conversion equation. 32. A computer device on which the program recorded on the medium according to claim 14 is installed.