Color comparison method and color comparison device

Abstract

To execute appropriate color comparison even when a reference object has color irregularities.SOLUTION: A color comparison device 1 executes: a reference information acquisition step (step S1) of acquiring colorimetric values of a plurality of reference points A1-Am in a reference object having color irregularities; a target information acquisition step (step S2) of acquiring colorimetric values of a plurality of measurement points B1-Bm in a target; a calculation step (step S4) of combining a reference point An and a measurement point Bn, and calculating the Euclidean distance L on color space coordinates between the combined reference point An and measurement point Bn; and a determination step (step S6) of comparing the Euclidean distance L calculated on the basis of at least any one combination of the combinations of the reference point An and measurement point Bn with a predetermined threshold Lth, to determine whether or not the color of the reference object and the color of the target are similar to each other.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a color comparison method and a color comparison apparatus.

Background Art

[0002] Conventionally, there has been a technique for evaluating the color of an object by comparing it with the color of a reference object. For example, in Patent Document 1, color data (for example, color difference and luminance) is extracted from each of a source image as a reference object and a copy image as an object, and the Mahalanobis distance of the color data is compared to obtain the similarity of the copy image to the source image.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the method described in Patent Document 1, when there is color unevenness in the reference object, it may not be possible to accurately determine whether the colors of the object and the reference object are similar.

Means for Solving the Problems

[0005] The color comparison method according to the present disclosure includes a reference information acquisition step of acquiring colorimetric values of a plurality of reference points in a reference object including color unevenness, an object information acquisition step of acquiring colorimetric values of a plurality of measurement points in an object, a calculation step of combining the reference points and the measurement points and calculating the Euclidean distance on a color space coordinate between the combined reference points and the measurement points, and a determination step of comparing the Euclidean distance calculated based on at least any one of the combinations of the reference points and the measurement points with a predetermined threshold value to determine whether the color of the reference object and the color of the object are similar.

[0006] The color comparison device according to the present disclosure includes a reference information acquisition unit that acquires color measurement values of a plurality of reference points in a reference object including color unevenness, an object information acquisition unit that acquires color measurement values of a plurality of measurement points in an object, a calculation unit that combines the reference points and the measurement points and calculates the Euclidean distance in the color space coordinates between the combined reference points and the measurement points, and a determination unit that determines whether the color of the reference object and the color of the object are similar by comparing the Euclidean distance calculated based on at least any one of the combinations of the reference points and the measurement points with a predetermined threshold value.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0008] An embodiment of the present disclosure will be described. FIG. 1 is a block diagram schematically showing a color comparison device 1 according to the present embodiment. The color comparison device 1 includes a spectroscope 10, a storage unit 20, a processor 30, a display unit 40, and an operation unit 50. This color comparison device 1 measures the color of an object and performs color comparison of the object with respect to a reference object.

[0009] FIG. 2 is a diagram showing an example of the spectroscope 10 mounted on the color comparison device 1. The spectroscope 10 includes a light source unit 11, a light guide unit 12, a spectroscopic filter 13, and a light receiving unit 14. The light source unit 11 includes a light source 11A and a condenser unit 11B, and the light emitted from the light source 11A is irradiated onto the object through the condenser unit 11B. The light guide unit 12 includes a reflecting mirror 12A and a band-pass filter 12B. The band-pass filter 12B is a filter that allows light in a predetermined wavelength range to enter from the incident light. For example, it transmits light with wavelengths in the visible light range and blocks light with other wavelengths. The light reflected by the object is reflected by the reflecting mirror 12A and enters the spectroscopic filter 13 via the band-pass filter 12B.

[0010] The spectroscopic filter 13 is a filter that transmits light with a predetermined wavelength from the incident light and can switch the transmission wavelength. For example, the spectroscopic filter 13 is a Fabry - Perot etalon, which includes a pair of opposed reflective films, and the transmission wavelength can be switched by changing the distance between the pair of reflective films. Note that the spectroscopic filter 13 may be other filters such as an AOTF (acousto - optic tunable filter) or an LCTF (liquid crystal tunable filter) in addition to the etalon element as described above.

[0011] The light receiving unit 14 is, for example, a photodiode, which receives the light transmitted through the spectroscopic filter 13 and outputs a detection signal corresponding to the received light amount. The detection signal output by the light receiving unit 14 is input to the processor 30 via a signal processing unit (for example, an I - V converter, an amplifier, and an AD converter) not shown in the figure.

[0012] The storage unit 20 in FIG. 1 records various programs and various data for controlling the color comparison device 1. Examples of the various programs recorded in the storage unit 20 include a spectroscopic measurement control program for controlling the spectroscope 10 and a color comparison program for performing color comparison of the object from the spectroscopic measurement results. In addition, examples of the various data stored in the storage unit 20 include table data for driving the above - mentioned spectroscopic filter 13 and a plurality of reference object data.

[0013] The reference object data is a data set corresponding to the reference object, and includes color measurement values, color measurement average values, the number of reference points A1 to A m in the reference object, and a threshold value Lth. The threshold value Lth may be a value preset based on a desired color comparison level through experiments, simulations, etc. The smaller the threshold value Lth, the more color comparisons (such as color identity determination) are performed at a higher similarity level. The reference object is any object including color unevenness, such as natural objects like plants, and images like designs showing color unevenness. m In addition, the reference object data may include any data indicating the positions of the reference points A1 to A in the reference object. For example, it may include image data indicating the positions of the reference points A1 to A m in the reference object. m The processor 30 is composed of an arithmetic circuit such as a CPU (Central Processing Unit), for example, and realizes various functions by reading and executing various programs stored in the storage unit 20. In this embodiment, the processor 30 reads and executes the color comparison program stored in the storage unit 20, and functions as a reference information acquisition unit 31, a target information acquisition unit 32, a calculation unit 33, a combination determination unit 34, and a determination unit 35 as shown in FIG. 1. Each of these functions will be described later.

[0014] The display unit 40 is a display, for example, and displays measurement guidance for the user, color determination results, etc. The operation unit 50 is a key or a touch display, for example, and accepts the user's input operations.

[0015] Next, the color comparison method in the color comparison device 1 of this embodiment will be described. FIG. 3 is a flowchart showing the color comparison method of this embodiment.

[0016] First, in response to the user's input operation, the reference information acquisition unit 31 selects the reference object data in the storage unit 20, and the plurality of reference points A1 to A in the reference object data

[0017] m ​Obtain each colorimetric value (step S1).

[0018] Next, when the spectrometer 10 is set on the object and an operation for performing spectroscopic measurement is input by the user, the target information acquisition unit 32 controls the spectrometer 10 to measure the colorimetric value at the measurement point B n on the object. Here, the spectrometer 10 changes the transmission wavelength of the spectroscopic filter 13 at a preset wavelength interval under the control of the target information acquisition unit 32, and measures the spectroscopic spectrum data at the measurement point B n in the visible light range. Then, the target information acquisition unit 32 calculates the colorimetric value at the measurement point B n based on the spectroscopic spectrum data at the measurement point B n . As the colorimetric value, for example, any color system such as XYZ values or L*a*b* values can be used. The colorimetric value corresponding to the measurement point B n is stored in the data reference area for color determination in the storage unit 20. Note that a known technique such as Japanese Patent Application Laid-Open No. 2017-49163 can be used as a method for calculating the colorimetric value from the spectroscopic spectrum data. Also, calibration using a white reference plate or the like may be performed before step S2.

[0019] Before performing the above step S2, the display unit 40 may display data indicating each position of the reference points A1 to A m on the reference object. In this case, the user refers to the data displayed on the display unit 40, sets the spectrometer 10 on the object so that the positional relationship of the plurality of reference points A1 to A m on the reference object is the same as the positional relationship of the plurality of measurement points B1 to B m on the object, and determines the arrangement of the measurement point B n . Here, "the same" is for the purpose of avoiding a large color deviation in the combination of the reference point A n determined in step S5 described later and the measurement point B n , and strict positional accuracy is not required.

[0020] Thereafter, the object information acquisition unit 32 acquires the reference points A1 to A2 in the reference object acquired in step S1. m and the number of color measurement points B of the measured object n The number is compared with the number (step S3). Color measurement point B of the target object n The number of reference points A1 to A m If the number is less than the number, a guide prompting measurement of the object is output to the display unit 40 or the like, and the process returns to step S2. On the other hand, the color measurement point B of the object n The number of reference points A1 to A m If the number of the reference points A1 to A2 is equal to the number of the reference points A1 to A2, the object information acquisition unit 32 ends the measurement of the object and proceeds to step S4. m The same number of measurement points B1 to B m The colorimetric values ​​of each of the colors are obtained.

[0021] Next, the calculation unit 33 calculates the measurement points B1 to B m For each of the reference points A1 to A m Each of these is combined in turn, and the combined reference point A n and measurement point B n In other words, the calculation unit 33 calculates the Euclidean distance L between the reference points A1 to A m and measurement points B1~B m A round-robin combination is created between and and the Euclidean distance L of each combination is calculated.

[0022] Next, the combination determination unit 34 determines whether the measurement point B n and reference point A n The sum of the Euclidean distances L of the combinations of the multiple reference points A1 to A m and multiple measurement points B1~B m Then, all combinations between the two, that is, m combinations, are determined (step S5).

[0023] Next, the determination unit 35 determines the reference points A1 to A m and measurement points B1~B mOf the m combinations with [object], select the maximum Euclidean distance Lmax calculated based on any one of the combinations, and determine whether this maximum Euclidean distance Lmax is less than or equal to a predetermined threshold Lth (step S6). This threshold Lth is, for example, a value included in the reference object data obtained in step S1. Note that the determination unit 35 increments the determination count M stored in the storage unit 20 as the implementation of step S6 progresses.

[0024] When the maximum Euclidean distance Lmax is less than or equal to the threshold Lth (step S6; YES), the determination unit 35 determines that the color of the object is similar to the color of the reference object. Thereafter, the determination unit 35 outputs the determination result to the display unit 40 or the like (step S7). Thus, the flowchart of FIG. 3 ends.

[0025] On the other hand, when the maximum Euclidean distance Lmax is greater than the threshold Lth (step S6; NO), the determination unit 35 determines whether the determination count M stored in the storage unit 20 is less than or equal to a predetermined repetition threshold Mth (step S8). This repetition threshold Mth is not particularly limited and may be any number. When the determination count M is less than or equal to the repetition threshold Mth (step S8; YES), the determination unit 35 outputs a guidance prompting remeasurement to the display unit 40 or the like and returns to step S2. At this time, the data of the measurement points B1 to B used in the immediately preceding color determination is deleted from the data reference area for color determination. m is deleted from the data reference area for color determination.

[0026] When the determination count M is greater than the repetition threshold Mth (step S8; NO), the determination unit 35 determines that the color of the object is not similar to the color of the reference object. Thereafter, the determination unit 35 outputs the determination result to the display unit 40 or the like (step S7). Thus, the flowchart of FIG. 3 ends.

[0027] Hereinafter, the case where the colorimetric values of three reference points A1, A2, A3 (see FIG. 4) and three measurement points B1, B2, B3 (see FIG. 5) are obtained by the above steps S1 to S3 will be exemplified. In step S4 above, for example, when calculating the Euclidean distance L_(A1 - B1) between the reference point A1 and the measurement point B1, it can be calculated by the following formula (1). [Equation] Also, in step S5 above, when calculating the sum S of the Euclidean distances in the case of combining A1 and B1, A2 and B2, and A3 and B3, this sum S can be calculated by the following formula (2). S = L_(A1 - B1)+L_(A2 - B2)+L_(A3 - B3) Equation (2)

[0028] When the three combinations of A1 and B1, A2 and B2, and A3 and B3 are determined by step S5 above, in step S6, among the Euclidean distances L_(A1 - B1), L_(A2 - B2), and L_(A3 - B3) based on these combinations, the one showing the maximum value is selected. If the Euclidean distance L_(A1 - B1) shows the maximum value, this Euclidean distance L_(A1 - B1) may be compared with a predetermined threshold value Lth.

[0029] [Function and Effect of the Present Embodiment] As described above, the color comparison device 1 of the present embodiment includes a reference information acquisition step (step S1) for acquiring the colorimetric values of a plurality of reference points A1 to A m in a reference object including color unevenness, a target information acquisition step (step S2) for acquiring the colorimetric values of a plurality of measurement points B1 to B m in a target object, and a calculation step (step S4) for combining the reference point A n and the measurement point B n and calculating the Euclidean distance L in the color space coordinates between the combined reference point A n and the measurement point B n and a calculation step (step S4) for calculating the Euclidean distance L in the color space coordinates between the combined reference point A n and the measurement point B nA determination step (step S6) is performed to determine whether the color of the reference object and the color of the target object are similar by comparing the Euclidean distance L calculated based on at least any one of the combinations with a predetermined threshold value Lth. According to the present embodiment, portions with various color densities in the reference object including color unevenness are used as reference points A n and a plurality of portions in the reference object are used as measurement points B. n As the reference point A n and the measurement point B n By using each color measurement value for determination, it is possible to perform an overall color similarity determination between the reference object and the target object. That is, in the present embodiment, even when there is color unevenness in the reference object, appropriate color comparison is possible. Further, in the present embodiment, since each position coordinate of the reference point A n in the reference object and the measurement point B n in the target object is not required, color comparison between the target object and the reference object can be easily performed.

[0030] In the present embodiment, the color measurement value is preferably represented by the L*A*B* color space system. Thereby, color comparison close to the user's perception can be performed.

[0031] The color comparison device 1 of the present embodiment further performs a combination determination step (step S5) for determining a combination of the reference point A n and the measurement point B n such that the sum of the Euclidean distances L between the reference object and the target object is minimized. The determination step (step S6) compares the Euclidean distance L calculated based on at least any one of the combinations of the reference point A n and the measurement point B n determined in the combination determination step (step S5) with a predetermined threshold value Lth. Thereby, not only in the case of the reference object but also when the target object has color unevenness, the reference point A n and the measurement point B n can be appropriately combined, and as a result, color comparison can be appropriately performed.

[0032] In this embodiment, the determination step (step S6) compares the maximum Euclidean distance Lmax calculated based on any one of the combinations of the reference points and the measurement points determined in the combination determination step (step S5) with the threshold value Lth. As a result, reference point A n and measurement point B n Among a plurality of combinations of, color comparison is performed by using the data of the combination with the most separated colors, so that it is possible to more appropriately determine whether the colors of the reference object and the target object are the same.

[0033] In this embodiment, the reference information acquisition step (step S1) acquires, as a set, the color measurement values, the color measurement average value, the number of measurement points, and the threshold value Lth of a plurality of reference points A1 to A in the reference object. As a result, the color comparison of this embodiment can be easily implemented. For example, it becomes possible for the user to select desired reference object data or use a threshold value Lth suitable for the reference object. m In this embodiment, the reference information acquisition step (step S1) acquires, as a set, the color measurement values, the color measurement average value, the number of measurement points, and the threshold value Lth of a plurality of reference points A1 to A in the reference object. As a result, the color comparison of this embodiment can be easily implemented. For example, it becomes possible for the user to select desired reference object data or use a threshold value Lth suitable for the reference object.

[0034] [Modification Example] The present invention is not limited to the above embodiment, and configurations obtained by modifications and improvements within the scope that can achieve the object of the present invention are included in the present invention.

[0035] In the above embodiment, the reference object data may not include the color measurement average value and the threshold value Lth. Also, in the above embodiment, the threshold value Lth is set for each reference object, but it may be constant.

[0036] In the above embodiment, the target information acquisition unit 32 calculates the color measurement value of the measurement point B based on the spectroscopic spectrum acquired from the spectroscope 10, but the color measurement value of the measurement point B may be acquired from an arbitrary database. n In the above embodiment, the target information acquisition unit 32 calculates the color measurement value of the measurement point B based on the spectroscopic spectrum acquired from the spectroscope 10, but the color measurement value of the measurement point B may be acquired from an arbitrary database. n of the measurement point B may be acquired.

[0037] [Modification Example 2] In step S6 of the above embodiment, the maximum Euclidean distance Lmax is compared with the threshold value Lth, but the present invention is not limited to this. For example, in step S5, the average value of the Euclidean distances L calculated from the combinations of the reference points A1 to A m and the measurement points B1 to B m may be compared with the threshold value Lth, or the minimum value of the Euclidean distances L calculated from any combination may be compared with the threshold value Lth.

[0038] [Modification Example 3] In step S5 of the above embodiment, all combinations between the reference points A1 to A m and the measurement points B1 to B m are determined so that the total sum of the Euclidean distances L is minimized, but the present invention is not limited to this. For example, in step S2 above, when the measurement order of the measurement points B n corresponding to the reference point A n is specified, the combination may be determined based on the measurement order.

[0039] [Modification Example 4] In the above embodiment, the spectroscope 10 may be a spectral camera that captures a spectral image. In this case, the target information acquisition unit 32 may calculate the color measurement value of the measurement point B n based on the average value of an arbitrary area (for example, 10 pixels × 10 pixels) in the spectral image. Alternatively, instead of the spectroscope 10, an RGB camera may be used. In this case, the target information acquisition unit 32 may acquire the color measurement value of the measurement point B n based on the captured image.

[0040] [Modification Example 5] In step S2 of the above embodiment, it has been described that the positional relationship of the plurality of measurement points B1 to B m on the object is made the same as the positional relationship of the plurality of reference points A1 to A m on the reference object, but the present invention is not limited to this. For example, by setting a large number of repetitions of the measurement in step S5, the effectiveness of the color comparison may be ensured.

[0041] [Modification Example 6] In step S1 of the above embodiment, the reference information acquisition unit 31 acquires reference object data such as color measurement values from the storage unit 20, but the present invention is not limited thereto. For example, the reference information acquisition unit 31 may acquire reference object data from another database that can communicate with the color comparison device 1. Further, the reference information acquisition unit 31 controls the spectroscope 10 to calculate the color measurement value of the reference point A n from the spectroscopic measurement result of the reference object.

[0042] [Summary of the Present Disclosure] The color comparison method according to the present disclosure includes a reference information acquisition step of acquiring color measurement values of a plurality of reference points in a reference object including color unevenness, an object information acquisition step of acquiring color measurement values of a plurality of measurement points in an object, combining the reference points and the measurement points, and calculating a Euclidean distance on a color space coordinate between the combined reference points and the measurement points, and a determination step of determining whether the color of the reference object and the color of the object are similar by comparing the Euclidean distance calculated based on at least any one of the combinations of the reference points and the measurement points with a predetermined threshold value.

[0043] In the color comparison method of this aspect, it is preferable that the color measurement value is represented by the L*A*B* color system.

[0044] The color comparison method of this aspect further includes a combination determination step of determining all combinations between the reference points and the measurement points so that the sum of the Euclidean distances between the reference object and the object is minimized, and the determination step preferably compares the Euclidean distance calculated based on at least any one of all combinations between the reference points and the measurement points determined in the combination determination step with a predetermined threshold value.

[0045] In the color comparison method of this aspect, it is preferable that the determination step compares the maximum Euclidean distance calculated based on any one of all combinations between the reference point and the measurement point determined in the combination determination step with the threshold value.

[0046] In the color comparison method of this aspect, it is preferable that the reference information acquisition step acquires, as a set, each color measurement value, the average color measurement value, the number of reference points, and the threshold value of the plurality of reference points in the reference object.

[0047] The color comparison apparatus according to the present disclosure includes a reference information acquisition unit that acquires color measurement values of a plurality of reference points in a reference object including color unevenness, an object information acquisition unit that acquires color measurement values of a plurality of measurement points in an object, a calculation unit that combines the reference points and the measurement points and calculates the Euclidean distance on the color space coordinates between the combined reference points and the measurement points, and a determination unit that determines whether the color of the reference object and the color of the object are similar by comparing the Euclidean distance calculated based on at least any one of the combinations of the reference points and the measurement points with a predetermined threshold value.

[0048] The color comparison apparatus of this aspect preferably further includes a display unit that displays data indicating the positions of the reference points in the reference object. Moreover, the color comparison apparatus of this aspect preferably further includes a display unit that displays the determination result by the determination unit.

Explanation of Signs

[0049] 1... Color comparison apparatus, 10... Spectrophotometer, 11... Light source unit, 11A... Light source, 11B... Condensing unit, 12... Light guide unit, 12A... Reflecting mirror, 12B... Band-pass filter, 13... Spectral filter, 14... Light receiving unit, 20... Storage unit, 30... Processor, 31... Reference information acquisition unit, 32... Object information acquisition unit, 33... Calculation unit, 34... Combination determination unit, 35... Determination unit, 40... Display unit, 50... Operation unit.

Claims

1. A reference information acquisition step of acquiring colorimetric values of a plurality of reference points in a reference object including color unevenness; An object information acquisition step of acquiring colorimetric values of a plurality of measurement points in an object; A calculation step of combining the reference points and the measurement points and calculating a Euclidean distance on a color space coordinate between the combined reference points and measurement points; A determination step of determining whether the color of the reference object and the color of the object are similar by comparing the Euclidean distance calculated based on at least any one of the combinations of the reference points and the measurement points with a predetermined threshold value. A color comparison method that performs the above steps.

2. The colorimetric value is represented by an L*A*B* color system. The color comparison method according to claim 1.

3. Further performing a combination determination step of determining all combinations between the reference points and the measurement points so that the sum of the Euclidean distances between the reference object and the object is minimized; The determination step compares the Euclidean distance calculated based on at least any one of all combinations between the reference points and the measurement points determined in the combination determination step with the threshold value. The color comparison method according to claim 1.

4. The determination step compares the maximum Euclidean distance calculated based on any one of all combinations between the reference points and the measurement points determined in the combination determination step with the threshold value. The color comparison method according to claim 3.

5. The reference information acquisition step acquires, as a set, each colorimetric value, colorimetric average value, the number of the reference points, and the threshold value of the plurality of reference points in the reference object. The color comparison method according to claim 1.

6. A reference information acquisition unit that acquires colorimetric values of a plurality of reference points in a reference object including color unevenness; An object information acquisition unit that acquires color measurement values of a plurality of measurement points on an object; A calculation unit that combines the reference point and the measurement point and calculates the Euclidean distance in the color space coordinates between the combined reference point and measurement point; A determination unit that determines whether the color of the reference object and the color of the object are similar by comparing the Euclidean distance calculated based on at least any one of the combinations of the reference point and the measurement point with a predetermined threshold value. A color comparison device comprising:

7. The color comparison device according to claim 6, further comprising a display unit that displays data indicating the position of the reference point on the reference object.

8. The color comparison device according to claim 6, further comprising a display unit that displays the determination result by the determination unit.

Images