KR101155992B1 - Detection method of invisible mark on card using mobile phone - Google Patents

Abstract

PURPOSE: A method for detecting an invisible mark on a card using a mobile phone is provided to reduce card detection time by detecting an invisible mark on a card using the color of light changed depending on the refractive index of wavelengths. CONSTITUTION: A method for detecting an invisible mark on a card using a mobile phone is as follows. A card image is obtained(S110). The colors of first, second, and third lights from the obtained card image are normalized(S120). The changed degree of the refractive index of the lights is displayed by the color difference of two normalized lights(S130). When the first, second, and third color differences are calculated, a histogram is stretched(S140).

Description

Detection method of Invisible Mark on Card using Mobile Phone

The present invention relates to a method of detecting a non-visible mark of a card using a mobile phone, and more particularly, a card photographed by a mobile phone using a characteristic of changing the color of light due to a difference in refractive index of a wavelength according to a medium in a visible light region. A method of detecting an invisible mark shown in the visible region.

Currently, the most widely used technology for fraudulent gambling using playing cards such as playing cards or playing cards is invisible material such as ultraviolet or infrared ink, which is displayed on the back of the card, and then used for special lenses, infrared cameras, or ultraviolet cameras. By using the method of criminals to grasp the contents of the card.

In general, when accused of fraudulent gambling or arresting a gambling site, police officers often need to find out if the card used is a fraudulent card.

In this case, the legal science research institute asks whether it is a fraudulent card or not. The appraiser or investigator usually conducts experiments using a special device equipped with a bandpass filter in the invisible light or invisible light such as ultraviolet light or infrared light. I could tell if there was a mark on the back of the card.

However, these special devices are expensive, and there is a problem that it takes a long time to investigate whether or not a fraudulent card because it is necessary to repeatedly irradiate light sources of various wavelengths.

The present invention has been made to solve the above-mentioned problems, the visible light is visible light on the invisible mark displayed on the card taken with the mobile phone using the characteristic that the color of the light is changed by the difference in the refractive index of the wavelength according to the medium in the visible light region Mobile phones can be detected in the area, so police officers can quickly identify fraudulent cards in investigations, and legal scientists do not have to examine the cards repeatedly over multiple wavelengths. It is to provide a method of detecting a non-visible mark of a card using.

Method for detecting the invisible mark of a card using a mobile phone of the present invention for achieving the above object, (a) the first light constituting each pixel in the extracted image of the card photographed through a camera embedded in the mobile phone, A normalization step of allowing the second light and the third light to be normalized to be calculated as the first normal light, the second normal light, and the third normal light; (b) The first color light shielding and the second color light shielding are calculated such that the color difference between two normal lights that are not overlapped with each other among the first normal light, the second normal light, and the third normal light normalized in step (a) is calculated. And a color difference calculating step of causing the third color light blocking; And (c) a histogram of the first color difference light, the second color light difference and the third color light difference calculated in step (b) to be calculated and then stretch the first and second distribution light to form one pixel. And an image acquisition step of acquiring the detected image of the card by causing the light and the third distributed light to be calculated respectively.

가 산출되도록 한 후 상기 명암값

의 합에 대한 평균 명암값

이 산출되도록 하여 상기 제1광, 제2광 및 제3광에 평균 명암값

이 각각 적용된 제1평균광, 제2평균광 및 제3평균광이 산출되도록 하는 단계와; 상기 제1평균광, 제2평균광 및 제3평균광 중 어느 하나의 평균광에 대한 히스토그램을 기준으로 나머지 2개의 평균광에 대한 히스토그램이 스트레칭 되도록 하여 정규화된 제1정규광, 제2정규광 및 제3정규광이 산출되도록 하는 단계를 포함할 수 있다.The normalization step is a contrast value for each pixel

After calculating the contrast value

Average contrast value for the sum of

To calculate the average contrast value for the first light, the second light and the third light.

Calculating the first average light, the second average light, and the third average light respectively applied thereto; The first normal light and the second normal light normalized by stretching the histogram for the remaining two average lights based on the histogram of the average light of any one of the first average light, the second average light, and the third average light. And allowing the third normal light to be calculated.

는

에 의해 산출되고, 상기 제1평균광, 제2평균광 및 제3평균광은

,

,

에 의해 각각 산출되며, 상기 제1정규광, 제2정규광 및 제3정규광은

,

,

에 의해 각각 산출될 수 있다.The contrast value

Is

The first average light, the second average light and the third average light is calculated by

,

,

Respectively calculated by the first normal light, the second normal light and the third normal light

,

,

Can be calculated respectively.

The color difference calculating step may include an absolute value for the difference between the first normal light and the second normal light, an absolute value for the difference between the first normal light and the third normal light, and an absolute value for the difference between the second normal light and the third normal light. And calculating the respective values so that the absolute values are matched with the first color light shielding, the second color light shielding, and the third color light shielding, respectively.

,

,

에 의해 각각 산출될 수 있다.The first color light blocking, the second color light blocking and the third color light blocking

,

,

Can be calculated respectively.

In the image acquisition step, the histograms of the first, second, and third color light blocks are respectively calculated, and the histograms are stretched, respectively, so that the first distributed light, the second distributed light, and the first It may include the step of causing each of the three distributed light.

The first distributed light, the second distributed light and the third distributed light

,

,

에 의해 각각 산출될 수 있다.

,

,

Can be calculated respectively.

According to the invisible mark detection method of the card using the mobile phone of the present invention as described above, the card photographed with the mobile phone using the characteristic that the color of the light is changed by the difference in the refractive index of the wavelength according to the medium in the visible light region By detecting the invisible mark in the visible range, the police can quickly identify fraudulent cards for investigation, and law scientists do not have to repeatedly scan the card for multiple wavelengths to check for fraudulent cards. There is an effect that the time can be shortened.

1 is an exemplary view showing an image of a card photographed using a mobile phone to detect the invisible mark in the card according to an embodiment of the present invention,
FIG. 2 is an exemplary view illustrating an image in which only a card part is extracted from the image of FIG. 1.
FIG. 3 is an exemplary diagram illustrating a histogram of a plurality of lights constituting pixels of an image in the image of FIG. 2.
4 is an exemplary diagram illustrating an example in which the remaining light is stretched based on one light in the histogram of FIG. 3.
5 is an exemplary view illustrating a state in which an invisible mark is detected in a card according to an embodiment of the present invention.
6 is an exemplary diagram illustrating a state in which noise is removed in a state where an invisible mark is detected in a card according to an embodiment of the present invention.
7 is a flowchart illustrating a method of detecting an invisible mark of a card using a mobile phone according to an embodiment of the present invention.
8 is an exemplary diagram illustrating an ultraviolet neck card in which an invisible mark is displayed in an ultraviolet region.
FIG. 9 is an exemplary view illustrating a state in which an invisible mark is detected using the ultraviolet neck card of FIG. 8 according to an embodiment of the present invention.
10 is an exemplary diagram illustrating an infrared neck card in which an invisible mark is displayed in an infrared region.
FIG. 11 is an exemplary diagram illustrating a state in which an invisible mark is detected using the infrared neck card of FIG. 10 according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

FIG. 1 is an exemplary view showing an image of a card photographed using a mobile phone for detecting an invisible mark in a card according to an embodiment of the present invention. FIG. 2 is an image of only a card part extracted from the image of FIG. 1. 3 is an exemplary diagram illustrating a histogram of a plurality of lights constituting a pixel of an image in the image of FIG. 2, and FIG. 4 is a diagram of stretching the remaining light based on one light in the histogram of FIG. 3. 5 is an exemplary diagram illustrating an example, and FIG. 5 is an exemplary diagram illustrating a state where an invisible mark is detected in a card according to an embodiment of the present invention, and FIG. 6 is a non-visible card in accordance with an embodiment of the present invention. 7 is a diagram illustrating a state in which noise is removed from a state in which a visibility mark is detected, and FIG. 7 is a flowchart illustrating a method of detecting an invisible mark of a card using a mobile phone according to an embodiment of the present invention.

In order to detect an invisible mark on a card, such as a trump or a card, using a mobile phone according to an embodiment of the present invention, as shown in FIG. 1, a user of a mobile phone (not shown) operates a mobile phone. The card image 100 must be acquired (step S110).

The mobile phone used in the present invention may be a cellular phone or a smart phone equipped with an internal or external camera, and a PDA (Personal Digital Assistant) or PMP (Portable Multimedia) equipped with other cameras. Player) and the like.

In addition, in the mobile phone used in the present invention, the method according to the step S110 and steps S120 to S150 described later are programmed and stored.

In particular, the process of the method according to the above-described step S110 to step S150 can be programmed into a single application and stored in the smart phone, and the card is driven through a camera provided in the smart phone by driving the application. You can shoot.

The process of producing an application running on a smartphone is a well-known matter, and thus a detailed description thereof will be omitted.

In the mobile phone used in the present invention, a storage unit (not shown) for storing a card image photographed by a camera and a card image stored in the storage unit are received and image processing is performed using the method according to steps S120 to S150 described later. An image processor (not shown) and a display unit (not shown) for displaying an image processed by the image processor is provided.

In addition, the mobile phone is provided with a user interface (not shown) for manipulation of card shooting.

The user interface unit is usually a key input unit, but may be an interface such as a joystick or a touch screen in some cases.

The storage unit may store not only the photographed image data but also data, application data, and the like that program the process of the method according to the above-described step S110 and the following steps S120 to S150.

The image processor performs a function of displaying a video signal photographed and input through a camera provided in a mobile phone on the display unit, and processing the image using the method according to steps S120 to S150, which will be described later. To transmit to the display unit.

The display unit may be formed of a liquid crystal display (LCD) or the like, and displays an image processed by the method according to steps S120 to S150 described later and various display data generated in the mobile phone. In this case, when the LCD is implemented using a touch screen method, the display unit may operate as a user interface unit.

As described above, when the card image 100 is stored in the storage unit by capturing the card using the mobile phone, the image processor detects the outermost line 210 of the card from the acquired card image 100 and extracts the extracted image. 200, and extracts a portion of the pattern 230 of the card from the extracted image 200.

The method used to extract the glyph 230 of the card is that most of the cards consist of black patterns between bright backgrounds, so that if the middle of the filter is dark and the outer edges of both are light, a window of weights is given. You can create a map by calculating the direction in 8 directions of horizontal, vertical, and diagonal directions.

Using the map generated as described above, binarization is performed by Otsu's method, and thinning is performed to extract only lines. Subsequently, when the line is extracted, the Hough transform is used to find the outermost line.

By binarizing only the innermost outer line based on the found outermost line, a portion of the pattern 230 in the card to be searched can be detected.

Since the color difference between the background and the pattern 230 part of the card is severe, it is necessary to select one part to reduce the error. Since the difference in color of the lighter part is better than the dark part of the experiment, the present invention selects only the lighter part and observes the changed form of the color.

To measure the degree of deformation of the color, three signals of the first light, red light (R), the second light, green light (G), and the third light, blue light (B), are inputted to the camera of the mobile phone that captures the image. The difference between the two should be measured.

Meanwhile, although the first light may be green or blue, the second light may be red or blue, and the third light may be red or green, in the present invention, the first light is consistently red, It is preferable to make the second light green and the third light blue.

The video contains a lot of noise.

In the case of a camera, light input to acquire an image is not a constant light, but different light comes in at various angles, and light intensity is also different.

In the case of a scanner, a certain amount of light comes in to acquire an image, but when the light is converted into a digital signal, the light passes through a lens first and then passes through an anti-aliasing filter and then a CFA (color filter array). And arrive at the pixel. The pixels absorb the photons of this light and convert them into signals using an A / D converter. After compression and gamma adjustment, compression is performed.

Therefore, as described above, since noise enters at each step for acquiring an image, the acquired image may not be uniform even when photographing a very uniform place.

Thus, a process of normalizing is necessary to remove the effect of the color change in accordance with the light intensity and the input characteristics of the first light, the second light, and the third light constituting the pixel (step S120).

가 산출되도록 한다.First, the contrast value for each pixel in the extracted image 200 obtained by Equation 1

To be calculated.

는 픽셀을 이루는 제1광,

는 픽셀을 이루는 제2광,

는 픽셀을 이루는 제3광, (x, y)는 픽셀의 좌표이다.here,

Is the first light constituting the pixel,

Is the second light constituting the pixel,

Is the third light constituting the pixel, and (x, y) is the coordinate of the pixel.

은 실제로는 전체 평균의 명암값과 같아야 한다.Then, the contrast value at one pixel

Should actually be equal to the contrast of the overall mean.

의 합에 대한 평균 명암값

이 산출되도록 하여 수학식 2에 의해 상기 제1광에 평균 명암값

이 적용된 제1평균광(260), 수학식 3에 의해 상기 제2광에 평균 명암값

이 적용된 제2평균광(270), 수학식 4에 의해 상기 제3광에 평균 명암값

이 적용된 제3평균광(280)이 산출되도록 한다.Therefore, the value of the pixel considering this value is the contrast value.

Average contrast value for the sum of

To calculate the average contrast value for the first light by

Is applied to the first average light 260, the average contrast value to the second light by the equation (3)

Is applied to the second average light 270, the average contrast value to the third light by the equation (4)

The applied third average light 280 is calculated.

는 제1광에 평균 명암값이 적용된 제1평균광(260),

는 제2광에 평균 명암값이 적용된 제2평균광(270),

는 제3광에 평균 명암값이 적용된 제3평균광(280)이다.
here,

Is the first average light 260 to which the average contrast value is applied to the first light,

Is a second average light 270 to which an average contrast value is applied to the second light,

Denotes a third average light 280 to which an average contrast value is applied to the third light.

Next, as shown in FIG. 3, histograms of the first average light 260, the second average light 270, and the third average light 280 are calculated, and as shown in FIG. 4. The first normal light 265, the second normal light 275, and the third normal light normalized by Equations 5 and 6 by stretching the histogram for the remaining two average lights based on the histogram for the average light. Causes light 285 to be calculated.

는 제1평균광(260)이 제2평균광(270)의 히스토그램을 기준으로 히스토그램 스트레칭된 제1정규광(265),

는 제3평균광(280)이 제2평균광(270)의 히스토그램을 기준으로 히스토그램 스트레칭된 제3정규광(285),

는 제2평균광(270)의 최소값,

는 제2평균광(270)의 최대값으로 나타낸다.here,

Denotes a first normal light 265 in which the first average light 260 is histogram stretched based on the histogram of the second average light 270,

Is a third normal light 285 in which the third average light 280 is histogram stretched based on the histogram of the second average light 270,

Is the minimum value of the second average light 270,

Denotes the maximum value of the second average light 270.

로 나타낼 수 있으며,

는 상기 제2평균광(270)과 동일하다.Here, the second normal light 275 is

Can be represented by

Is the same as the second average light 270.

In this way, the intensity of the plurality of lights constituting the pixel is made constant, and the histograms of the first average light 260 and the third average light 280 are adjusted based on the histogram of the second average light 270 to maximize the light. Removed the effects of color and distortion

In the present invention, the histogram for the first average light 260 and the third average light 280 is stretched based on the histogram for the second average light 270, but the present invention is not limited thereto. The histogram for the second average light 270 and the third average light 280 may be stretched based on the histogram for the first average light 260 based on the histogram for the third average light 280. ) And the second average light 270 may be stretched.

On the other hand, when two different media are in contact with each other, the path of light passing through the medium is bent because the light flux is different for each medium, and the degree of deformation of the refractive index of the light according to the color medium is the first normal light 265 and the second normal. The light 275 and the third normal light 285 may be represented by the color difference of two normal lights which do not overlap each other (step S130).

Therefore, the color difference between the first normal light 265 and the second normal light 275, the color difference between the first normal light 265 and the third normal light 285, and the second normal light 275 and the second light. It can be represented by the color difference of the 3 normal light (285).

First, the absolute value of the difference between the first normal light 265 and the second normal light 275 is calculated by Equation 7, and the first normal light 265 and the third normal light are expressed by Equation 8 The absolute value of the difference of 285 is calculated, and the absolute value of the difference between the second normal light 275 and the third normal light 285 is calculated by Equation (9).

Subsequently, the first color difference light, the second color light difference and the third color light difference are calculated by matching each absolute value with the first color light, the second color light and the third color light, respectively, which constitute one pixel.

는 제1정규광(265)과 제2정규광(275)의 차이에 대한 절대값에 매칭되는 제1색차광,

는 제1정규광(265)과 제3정규광(285)의 차이에 대한 절대값에 매칭되는 제2색차광,

는 제2정규광(275)과 제3정규광(285)의 차이에 대한 절대값에 매칭되는 제3색차광이다.here,

Is the first color difference light matching an absolute value for the difference between the first normal light 265 and the second normal light 275,

Is a second color light blocking matched to an absolute value of the difference between the first normal light 265 and the third normal light 285,

Is a third color difference light that matches an absolute value for the difference between the second normal light 275 and the third normal light 285.

However, this color difference is different in degree of deformation according to the angle of light and the difference is different.

Accordingly, when the first, second, and third color light shields are calculated, the histograms are calculated, and the histograms are stretched to have an even distribution by using Equations 10, 11, and 12, respectively. S140).

는 제1색차광에 대한 히스토그램 스트레칭으로 산출된 제1분포광,

는 제1색차광의 최소값,

는 제1색차광의 최대값,

는 제2색차광에 대한 히스토그램 스트레칭으로 산출된 제2분포광,

는 제2색차광의 최소값,

는 제2색차광의 최대값,

는 제3색차광에 대한 히스토그램 스트레칭으로 산출된 제3분포광,

는 제3색차광의 최소값,

는 제3색차광의 최대값이다.here,

Is the first distributed light calculated by histogram stretching for the first color light shielding,

Is the minimum value of the first color block,

Is the maximum value of the first color block,

Is the second distributed light calculated by histogram stretching for the second light shielding,

Is the minimum value of the second color block,

Is the maximum value of the second color block,

Is the third distributed light calculated by histogram stretching for the third color shading,

Is the minimum value of the third color shading,

Is the maximum value of the third color light shielding.

In this way, the first distributed light, the second distributed light, and the third distributed light, which form one pixel, are respectively calculated so that the first detected image in which the invisible mark 350 of the card is displayed, as shown in FIG. 5. 300 can be obtained.

On the other hand, since the thickness of the ink for forming the invisible mark 350 in the card is constant, the degree of deformation of the color of light passing through the invisible mark 350 should appear the same and should change smoothly according to the difference in the light source.

However, the white Gaussian noise is actually generated in the first detected image 300 through the first distributed light, the second distributed light, and the third distributed light, which are calculated by Equations 10 to 12 to form one pixel. It has a lot of noise.

Therefore, the Warner filter is used as a probabilistic reconstruction method for minimizing the difference between the original image and the reconstructed image in terms of minimum mean square error (MMSE) to remove noise (step S150).

Subsequently, by using the Wiener filter, the second detection image 400 displaying the invisible mark 450 from which the noise is removed is displayed by removing unintentionally entered or splashed values. And is displayed through the display unit.

8 is an exemplary view illustrating an ultraviolet neck card in which an invisible mark is displayed in an ultraviolet region, and FIG. 9 illustrates a state in which an invisible mark is detected by the method according to an embodiment of the present invention. 10 is an exemplary diagram illustrating an infrared neck card in which an invisible mark is displayed in an infrared region, and FIG. 11 is an invisible method of the infrared neck card of FIG. 10 according to an embodiment of the present invention. It is an exemplary figure which shows the state which detected the mark.

Among the cards displaying the above-mentioned invisible mark, as shown in FIG. 8, an ultraviolet neck card in which the invisible mark 515 is displayed in the ultraviolet image 510 and an infrared image 610 as shown in FIG. 10. There is an infrared neck card in which the invisible mark 615 is displayed.

As a result of photographing these two types of card images with the mobile phone and processing them according to an embodiment of the present invention, as shown in FIGS. 9 and 11, the ultraviolet images 510 in the visible light images 530 and 630. Or similar to the result displayed on the infrared image 610, it can be seen that the invisible marks 535 and 635 are respectively displayed through the display unit.

Therefore, the method according to the above-described step S110 to step S150 is programmed to be stored as a single application and stored in the smart phone, and later drive the application to the user to illuminate the card through the camera of the smart phone, Figure 9 and As shown in FIG. 11, invisible marks 535 and 635 are displayed in the visible light images 530 and 630 similarly to the results displayed in the ultraviolet image 510 or the infrared image 610.

Doing so can prevent fraudulent victims of fraudulent gambling and can also help casinos and other businesses find out if they are fraudulent.

In addition, the method according to the steps S110 to S150 according to the present invention can be programmed and stored in a recording medium such as a CD-ROM, a memory, a ROM, and an EEPROM so that a computer can read the mobile phone including a smart phone.

Therefore, the method according to an embodiment of the present invention may be stored in a scanner, a general camera, or the like and used to detect an invisible mark.

On the other hand, if the camera is provided but the method according to an embodiment of the present invention is not stored by programming or a mobile phone without an application, the method according to an embodiment of the present invention by recording a card is stored or programmed The card image can be transmitted to the installed mobile phone.

Therefore, the invisible mark of the card can be detected by the method according to the present invention in the mobile phone receiving the card image.

In the above description, the present invention has been described with reference to preferred embodiments, but the present invention is not necessarily limited thereto, and a person having ordinary skill in the art to which the present invention pertains does not depart from the technical spirit of the present invention. It will be readily appreciated that various substitutions, modifications and variations can be made.

200: extracted image 265: first normal light
275: second normal light 285: third normal light
300: first detection image

Claims (9)

(a) In the extracted image 200 of the card photographed or transmitted through the camera built in the mobile phone, the first normal light, the second light and the third light constituting each pixel are normalized. 265, a normalization step of calculating the second normal light 275 and the third normal light 285;
(b) color differences of two normal lights, which are not overlapped with each other, among the first normal light 265, the second normal light 275, and the third normal light 285 normalized in step (a) are calculated, respectively. A color difference calculating step of causing the first color light blocking, the second color light blocking, and the third color light blocking; And
(c) The first distributed light and the second distributed light, which form one pixel by stretching the histogram of the first, second, and third color light beams calculated in step (b), and then stretching the light. And an image acquisition step of acquiring the detected image 300 of the card by calculating the third distributed light respectively.
Invisible mark detection method of the card using a mobile phone comprising a. The method of claim 1, wherein the normalization step
Contrast value for each pixel

After calculating the contrast value

Average contrast value for the sum of

To calculate the average contrast value for the first light, the second light and the third light.

Calculating the first average light 260, the second average light 270, and the third average light 280 respectively applied thereto;
Normalized by stretching the histogram for the remaining two average lights based on the histogram of any one of the first average light 260, the second average light 270, and the third average light 280. The first normal light (265), the second normal light (275) and the third normal light (285) comprising the step of calculating the invisible mark detection method of the card using a mobile phone. The method of claim 2,
The contrast value

Is

Calculated by

Is the first light constituting the pixel,

Is the second light constituting the pixel,

Is the third light constituting the pixel, (x, y) is the coordinate of the pixel),
The first average light 260, the second average light 270 and the third average light 280

,

,

Calculated by, where

Is the first average light to which the average contrast value is applied to the first light,

Is the second average light to which the average contrast value is applied to the second light,

Is the third average light to which the average contrast value is applied to the third light),
The first normal light 265, the second normal light 275 and the third normal light 285 are

,

,

Calculated by, where

Is a first normal light whose first average light is histogram stretched based on the histogram of the second average light,

Is a third normal light whose third average light is histogram stretched based on the histogram of the second average light,

Is the second normal light and is the same as the second average light,

Is the minimum value of the second average light,

Is the maximum value of the second average light) method of detecting the invisible mark of a card using a mobile phone. The method of claim 3, wherein the color difference calculating step
The absolute value of the difference between the first normal light 265 and the second normal light 275, the absolute value of the difference between the first normal light 265 and the third normal light 285 and the second normal light ( 275) and an absolute value for the difference between the third normal light 285 are respectively calculated so that each absolute value is matched with the first color light shield, the second color light shield, and the third color light shield, respectively. Invisible mark detection method of a card using a mobile phone, characterized in that. The method of claim 4, wherein the first color light shielding, the second color light shielding and the third color light shielding

,

,

Calculated by, where

Is the first color difference light matching the absolute value of the difference between the first normal light and the second normal light,

Is a second color light shield matching an absolute value for the difference between the first normal light and the third normal light,

And a third color light shield matched to an absolute value for the difference between the second normal light and the third normal light). The method of claim 5, wherein the image acquisition step
Histograms of the first, second, and third color light blocks are calculated, and the histograms are stretched, respectively. Method for detecting the invisible mark of the card using a mobile phone, characterized in that it comprises the step of calculating. The method of claim 6,
The first distributed light, the second distributed light and the third distributed light

,

,

Calculated by, where

Is the first distributed light calculated by histogram stretching for the first color light shielding,

Is the minimum value of the first color block,

Is the maximum value of the first color block,

Is the second distributed light calculated by histogram stretching for the second light shielding,

Is the minimum value of the second color block,

Is the maximum value of the second color block,

Is the third distributed light calculated by histogram stretching for the third color shading,

Is the minimum value of the third color shading,

Is the maximum value of the third color light shielding). A computer-readable recording medium having recorded thereon a program for executing the method for detecting an invisible mark of a card using a mobile phone according to any one of claims 1 to 7. A recording medium which is produced by an application and stores a program for executing the invisible mark detection method of a card using a mobile phone according to any one of claims 1 to 7.

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