Palmar vein effective area extraction and correction method, identification method and storage medium
By detecting and correcting the effective area and finger root point in palm vein images, the problems of interference areas and inconsistent palm orientation in palm vein images are solved, thus improving the accuracy of palm vein recognition.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN MAXVISION TECH
- Filing Date
- 2022-12-21
- Publication Date
- 2026-06-09
AI Technical Summary
When acquiring palm vein images, there are often interfering areas outside the palm and the palm orientation is not fixed, which increases the difficulty of subsequent identification.
By detecting the rectangular effective area in the palm vein image and locating the four finger root points, the left and right hands are determined, the finger direction is adjusted to face upwards, and the palm vein ROI and finger root points are detected using the SCRFD network to perform orientation rotation correction, remove interference areas, and unify the palm orientation.
It effectively eliminates interference areas outside the palm, standardizes palm orientation, reduces the difficulty of subsequent recognition, and improves the accuracy of palm vein recognition.
Smart Images
Figure CN116168422B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of image processing, and more specifically, to a method for extracting and correcting the effective area of palm veins, a recognition method, and a storage medium. Background Technology
[0002] Currently, fingerprint recognition and facial recognition are two common and mature identification technologies, widely used in identification, security checks, access control, and medical research. Palm vein recognition, as a more secure biometric feature, has been studied for decades. Its non-contact and non-bio-identification characteristics make it highly promising for identification in public places.
[0003] Useful features for palm vein recognition are often those in the palm center region, also known as the effective palm vein region. However, when acquiring palm vein images, areas outside the palm, such as finger vein regions and background areas outside the palm, are often included as interference. Furthermore, due to the randomness of the acquisition process, the orientation of the palm in the palm vein image may be arbitrary, with no fixed and uniform angle. All of these phenomena increase the difficulty of subsequent palm vein recognition. Summary of the Invention
[0004] In view of the prior art, this application aims to provide a method for extracting and correcting the effective area of palm veins. This method extracts the effective area of palm veins in palm vein images to exclude interference areas other than the palm area, and unifies the palm orientation angle in the effective area of palm veins, so as to eliminate unnecessary interference areas and angles in the subsequent palm vein recognition process.
[0005] To address the aforementioned technical problems, this application provides a method for extracting and correcting the effective area of palm veins, comprising:
[0006] Obtain palm vein images;
[0007] The rectangular effective area of the palm vein in the palm vein image is detected, and four finger root points in the effective area of the palm vein are located. The four finger root points include the point between the root of the thumb and the root of the index finger, the point between the root of the index finger and the root of the middle finger, the point between the root of the middle finger and the root of the ring finger, and the point between the root of the ring finger and the root of the little finger.
[0008] Determine whether the effective area of the palmar vein belongs to the left or right hand based on the four finger base points; and...
[0009] Adjust the effective area of the palm vein so that the fingers are pointing upwards. Based on the structural characteristics of the left and right hands, perform orientational rotation correction on the effective area of the palm vein so that the point between the base of the index finger and the base of the middle finger and the point between the base of the middle finger and the base of the ring finger are on the same horizontal line parallel to the X-axis.
[0010] In one possible implementation, the four finger root points within the effective region of the palmar vein are located as follows:
[0011] x n '=x n -x src ;y n '=y n -y src ;
[0012] Where, x n 'and y n 'Locate the nth key point P respectively n x and y coordinates n and y n These are the nth key points P in the original palm vein image. n x and y coordinates; src and y src The x and y coordinates are the upper left corner of the effective area of the detected rectangular palm vein.
[0013] In one possible implementation, the points between the bases of the thumb and index finger, the index finger and middle finger, the middle finger and ring finger, and the ring finger and little finger are respectively designated as key points P1, P2, P3, and P4. The steps for determining whether the effective area of the detected palmar vein belongs to the left or right hand based on these four finger root points include:
[0014] Establish a two-dimensional rectangular coordinate system with the key point P1 as the origin;
[0015] Calculate the deflection angle α of the lines connecting P2, P3, P4 and P1 relative to the X-axis. n1 , where n∈(2,3,4);
[0016] Determine whether P2, P3, and P4 are located in the same quadrant of a two-dimensional rectangular coordinate system with the key point P1 as the origin;
[0017] If so, based on the deflection angle α corresponding to P2, P3, and P4 21 α 31 and α 41 To determine whether the effective area of the palmar vein belongs to the left or right hand;
[0018] If not, select two key points P located in the same quadrant. i and P j According to P i and P j The corresponding deflection angle α i1 and α j1To determine whether the effective area of the palm vein belongs to the left or right hand, i∈(2,3,4), j∈(2,3,4) and i<j.
[0019] In one possible implementation, based on the deflection angles α corresponding to P2, P3, and P4... 21 α 31 and α 41 To determine whether the effective area of the palmar vein belongs to the left or right hand, specifically:
[0020] If α 21 >α 31 >α 41 The effective area for palmar veins is from the left hand;
[0021] If α 21 <α 31 <α 41 The effective area of the palmar vein comes from the right hand.
[0022] In one possible implementation, according to P i and P j The corresponding deflection angle α i1 and α j1 To determine whether the effective area of the palmar vein belongs to the left or right hand, specifically:
[0023] Calculate the deflection angle difference Δα = α i1 -α j1 ;
[0024] If Δα > 0, then the effective area of the palmar vein originates from the left hand;
[0025] If Δα < 0, then the effective area of the palmar vein comes from the right hand.
[0026] In one possible implementation, α n1 =arctan((y n '-y1') / (x n '-x1'));
[0027] Where, x n 'and y n 'These are the nth key points P' n The x and y coordinates are given, and x1' and y1' are the x and y coordinates of the first key point P1, respectively.
[0028] In one possible implementation, the step of azimuthally rotating and correcting the effective area of the palmar veins based on the structural characteristics of the left and right hands, so that the point between the base of the index finger and the base of the middle finger and the point between the base of the middle finger and the base of the ring finger are located on the same horizontal line parallel to the X-axis, includes:
[0029] Select key points P2 and P4;
[0030] For the palmar veins belonging to the right hand, calculate the orientation rotation angle β = arctan((y4'-y2') / (x4'-x2'));
[0031] For the palmar veins belonging to the left hand, calculate the orientation rotation angle β = arctan((y2'-y4') / (x2'-x4'));
[0032] If the orientation rotation angle β is greater than 0, then the effective area of the palm vein will be rotated counterclockwise around the center point of the image by angle β.
[0033] If the orientation rotation angle β is less than 0, then the effective area of the palm vein will be rotated clockwise around the center point of the image by angle β.
[0034] Where x2' and y2' are the x and y coordinates of the second key point P2, respectively, and x4' and y4' are the x and y coordinates of the fourth key point P4, respectively.
[0035] In one possible implementation, after azimuth rotation correction of the effective area of the palm vein, the method for extracting and correcting the effective area of the palm vein further includes:
[0036] Calculate the x-coordinate of key points P2 and P4 after rotation and their y-coordinate in the direction of the x-axis.
[0037] Remove pixels in the effective area of the palm vein whose ordinate value is less than the ordinate value of the rotated keypoint P2, and / or remove pixels in the effective area of the palm vein whose ordinate value is less than the ordinate value of the rotated keypoint P4.
[0038] This application also provides an identification method, which includes processing a palm vein image library and a palm vein image to be identified using the palm vein effective region extraction and correction method; and using a palm vein identification algorithm to identify and compare the processed palm vein image to be identified and the processed palm vein image library.
[0039] This application also provides a computer-readable storage medium for storing a computer program, which, when executed by a processor, implements the method for extracting and correcting the effective area of the palm vein.
[0040] The beneficial effects of the palm vein effective region extraction and correction method provided in this application are as follows: it extracts the effective region of the palm vein in the palm vein image to exclude interference areas other than the palm area; it determines whether the extracted effective region of the palm vein belongs to the left or right hand, and adjusts the effective region of the palm vein so that the fingers face upwards. According to the structural characteristics of the left and right hands, the points between the bases of the index and middle fingers and between the bases of the middle and ring fingers in the effective region of the palm vein in both hands are located on the same horizontal line parallel to the X-axis. This can unify the palm orientation angle in the effective region of the palm vein. Therefore, this palm vein effective region extraction and correction method effectively eliminates interference areas as much as possible for subsequent palm vein recognition and eliminates the influence of palm angle on palm vein recognition. Attached Figure Description
[0041] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0042] Figure 1 This is a flowchart illustrating the method for extracting and correcting the effective area of palm veins according to an embodiment of this application.
[0043] Figure 2 This is a schematic diagram illustrating the left palmar vein ROI and four finger root points in an embodiment of this application.
[0044] Figure 3 This is a schematic diagram showing the right palmar vein ROI and the four finger root points in an embodiment of this application;
[0045] Figure 4 This is a schematic diagram showing the result of the SCRFD network detecting veins in a right palm image according to an embodiment of this application.
[0046] Figure 5 for Figure 4 The final effective area of the palm vein and the results of four finger root points within the effective area of the palm vein obtained from the palm vein image;
[0047] Figure 6 This is a flowchart illustrating the steps of determining whether the effective area of the detected palm vein belongs to the left or right hand based on four finger root points, according to an embodiment of this application.
[0048] Figure 7 This is a schematic diagram showing the deflection angles of the left and right key points P2, P3, and P4 in each quadrant of an embodiment of this application.
[0049] Figure 8This is a schematic diagram showing the result of azimuth rotation correction of the effective area of the left palm vein in an embodiment of this application. Detailed Implementation
[0050] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.
[0051] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.
[0052] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.
[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0054] The method for extracting and correcting the effective area of palm veins, the identification method, and the computer-readable storage medium of this application are now described in detail with reference to the accompanying drawings.
[0055] Please refer to Figure 1 The method for extracting and correcting the effective area of palm veins provided in this application includes the following steps S100 to S400.
[0056] Step S100: Obtain palm vein image.
[0057] Step S200: Detect the rectangular effective area of the palm vein in the palm vein image and locate the four finger root points in the effective area of the palm vein. The four finger root points include the point between the root of the thumb and the root of the index finger, the point between the root of the index finger and the root of the middle finger, the point between the root of the middle finger and the root of the ring finger, and the point between the root of the ring finger and the root of the little finger.
[0058] Step S300: Determine whether the effective area of the palmar vein originates from the left or right hand based on the four finger root points.
[0059] Step S400: Adjust the effective area of the palm vein so that the fingers are pointing upwards. According to the structural characteristics of the left and right hands, perform orientation rotation correction on the effective area of the palm vein so that the point between the base of the index finger and the base of the middle finger and the point between the base of the middle finger and the base of the ring finger are on the same horizontal line parallel to the X-axis.
[0060] In the above embodiment, the effective area of the palm vein is the vein area in the center of the palm. An image coordinate system is established with the upper left corner of the image as the origin. The effective area of the palm vein is adjusted so that the fingers point upwards. This unifies the effective area of the palm vein to the direction that the human eye is accustomed to viewing. Unifying the finger orientation of the effective area of the palm vein facilitates subsequent orientation rotation correction.
[0061] In one embodiment, a lightweight detection network based on SCRFD is used to detect palm vein ROIs and four finger root points. During the training phase, near-infrared palm vein images at different rotation angles are first acquired using a camera, and the effective ROIs of the left and right palm veins and four finger root keypoints are labeled respectively. The ROI labels include the coordinates and category of the bounding box, where the category refers to the effective palm vein area. The four finger root keypoints are labeled with their two-dimensional coordinate values, and the labeling order is fixed from thumb to little finger. The points between the thumb and index finger root, the index and middle finger root, the middle and ring finger root, and the ring and little finger root are labeled as keypoints P1, P2, P3, and P4, respectively. Then, the palm vein images and labels are input to train the SCRFD network. During the inference phase, palm vein images at any angle are input, and the SCRFD network can quickly output the coordinates of the palm vein ROI detection box and the coordinates of the four finger root points. Figure 2 A schematic diagram showing the ROI of the left palmar vein and the markings of the four finger bases; Figure 3 A schematic diagram showing the ROI of the right palmar vein and the four finger root points; Figure 4 This is a schematic diagram showing the results of SCRFD network detecting veins in a right palm image. Figure 5 for Figure 4 The final effective area of the palm vein and the results of four finger root points within the effective area of the palm vein obtained from the palm vein image.
[0062] Furthermore, the coordinates of the four finger root points detected by the SCRFD network are the original coordinates in the original palmar vein image, and the four finger root points in the effective region of the palmar vein are located as follows: x n '=x n -x src ;y n '=yn -y src .
[0063] Where, x n 'and y n 'Locate the nth key point P respectively n x and y coordinates; n and y n These are the nth key points P in the original palm vein image. n The x and y coordinates, i.e., the nth keypoint P in the palm vein image detected using the SCRFD network. n x and y coordinates; src and y src The x and y coordinates are the upper left corner of the effective area of the detected rectangular palm vein.
[0064] In one embodiment, the points between the bases of the thumb and index finger, the index finger and middle finger, the middle finger and ring finger, and the ring finger and little finger are respectively designated as key points P1, P2, P3, and P4; these four finger base points are then designated as key points P1, P2, P3, and P4 sequentially from thumb to little finger. For step S300, refer to... Figure 6 The steps for determining whether the effective area of the detected palmar vein belongs to the left or right hand based on the four finger base points include:
[0065] Step S310: Establish a two-dimensional rectangular coordinate system with key point P1 as the origin;
[0066] Step S320: Calculate the deflection angle α of the lines connecting P2, P3, P4 and P1 relative to the X-axis direction. n1 , where n∈(2,3,4);
[0067] Step S330: Determine whether P2, P3 and P4 are located in the same quadrant of a two-dimensional rectangular coordinate system with key point P1 as the origin; if yes, proceed to step S340, otherwise proceed to step S350.
[0068] Step S340: Based on the deflection angles α corresponding to P2, P3, and P4 21 α 31 and α 41 To determine whether the effective area of the palmar vein belongs to the left or right hand;
[0069] Step S350: Select two key points P located in the same quadrant. i and P j According to P i and P j The corresponding deflection angle α i1 and αj1 To determine whether the effective area of the palm vein belongs to the left or right hand, i∈(2,3,4), j∈(2,3,4) and i<j.
[0070] In step S320, the deflection angle α n1 The formula for calculating α is: n1 =arctan((y n '-y1') / (x n '-x1'));
[0071] Where, x n 'and y n 'These are the nth key points P' n The x and y coordinates are given, and x1' and y1' are the x and y coordinates of the first keypoint P1, respectively. n '、y n x1' and y1' can be calculated using the method in step S200.
[0072] Among them, such as Figure 7 As shown, in a two-dimensional rectangular coordinate system established with key point P1 as the origin, the diagram illustrates the deflection angles of the lines connecting key points P2, P3, and P4 of the left and right hands in the same quadrant to P1 relative to the X-axis. For step S340, based on the deflection angles α corresponding to P2, P3, and P4... 21 α 31 and α 41 To determine whether the effective area of the palmar vein belongs to the left or right hand, specifically: if it is α 21 >α 31 >α 41 The effective area for palmar veins is from the left hand; if it is α 21 <α 31 <α 41 The effective area of the palmar vein comes from the right hand.
[0073] Specifically, in step S350, two key points P located in the same quadrant are selected. i and P j According to P i and P j The corresponding deflection angle α i1 and α j1 To determine whether the effective area of the palmar vein belongs to the left or right hand, specifically:
[0074] Calculate the deflection angle difference Δα = α i1 -α j1 ;
[0075] If Δα > 0, then the effective area of the palmar vein originates from the left hand;
[0076] If Δα < 0, then the effective area of the palmar vein comes from the right hand.
[0077] It is worth noting that in a two-dimensional rectangular coordinate system established with P1 as the origin, key points P2, P3, and P4 are either in the same quadrant or not in the same quadrant. Step S340 deals with the case where they are in the same quadrant. Step S350 deals with the case where they are not in the same quadrant. For key points P2, P3, and P4 that are not in the same quadrant, according to the structural characteristics of the palm, there will be two key points in the same quadrant, that is, either key points P2 and P3 are in the same quadrant, or key points P3 and P4 are in the same quadrant. Taking key points P2 and P3 as being in the same quadrant as an example, when △α=α 21 -α 31 When Δα is greater than 0, the effective area of the palmar vein originates from the right hand. 21 -α 31 When the value is less than 0, the effective area of the palm vein originates from the left hand.
[0078] In one embodiment, step S400, adjusting the effective area of the palm vein with the fingers pointing upwards and performing orientational rotation correction on the effective area of the palm vein according to the structural characteristics of the left and right hands, so that the point between the base of the index finger and the base of the middle finger and the point between the base of the middle finger and the base of the ring finger are located on the same horizontal line parallel to the X-axis, includes:
[0079] Step S410: Select key points P2 and P4;
[0080] Step S420: For the palmar veins belonging to the right hand, calculate the orientation rotation angle β = arctan((y4'-y2') / (x4'-x2'));
[0081] Step S430 For the palmar veins belonging to the left hand, calculate the orientation rotation angle β = arctan((y2'-y4') / (x2'-x4'));
[0082] Step S440: If the orientation rotation angle β is greater than 0, then rotate the effective area of the palm vein counterclockwise around the center point of the image by angle β.
[0083] Step S450: If the orientation rotation angle β is less than 0, then rotate the effective area of the palm vein clockwise around the center point of the image by angle β.
[0084] In the above steps, x2' and y2' are the x-coordinate and y-coordinate of the second key point P2, respectively, and x4' and y4' are the x-coordinate and y-coordinate of the fourth key point P4, respectively.
[0085] It is worth noting that the structural characteristics of the left and right hands have the following features: the effective area of the palmar veins is uniformly adjusted so that the fingers point upwards; the arrangement order of key points P2 and P4 in the left palmar veins is exactly the opposite of that in the right palm. For the same rotation angle β calculation method, the starting point is the second key point of P2 and P4 in the positive X-axis direction, and the ending point is the first key point of P2 and P4 in the positive X-axis direction. Figure 8 A schematic diagram showing the result of azimuth rotation correction of an effective area of the left palmar vein.
[0086] In the above embodiments, after azimuth rotation correction of the effective area of the palm vein, the method for extracting and correcting the effective area of the palm vein further includes:
[0087] Step S500: Calculate the x-coordinate of key points P2 and P4 after rotation and the y-coordinate of key points P2 and P4.
[0088] Step S600: Remove pixels in the effective area of the palm vein whose ordinate value is less than the ordinate value of the key point P2 after rotation, and / or remove pixels in the effective area of the palm vein whose ordinate value is less than the ordinate value of the key point P4 after rotation.
[0089] It is worth noting that in the image after being uniformly adjusted to have the fingers pointing upwards and after orientation rotation correction, the pixels above key points P2 and P4 do not cover the vein features of the palm. Therefore, the processing in steps S500 and S600 can further remove background interference from non-vein effective areas, providing as many vein features as possible for subsequent vein recognition and reducing interference from non-vein areas, which helps to improve the accuracy of subsequent vein recognition.
[0090] In step S500, after azimuth rotation correction of the effective area of the palm vein, key points P2 and P4 are rotated to become... and in and The coordinates are:
[0091]
[0092] in, and They are respectively x and y coordinates and They are respectively The x and y coordinates.
[0093] In the aforementioned method for extracting and correcting the effective area of palm veins, the effective area of palm veins in the palm vein image is extracted to exclude interference areas other than the palm region. Furthermore, it is determined whether the extracted effective area of palm veins belongs to the left or right hand, and the effective area of palm veins is adjusted so that the fingers point upwards. Based on the structural characteristics of both the left and right hands, the points between the bases of the index and middle fingers and between the bases of the middle and ring fingers in the effective area of palm veins for both hands are located on the same horizontal line parallel to the X-axis. This unifies the palm orientation angle within the effective area of palm veins. Therefore, this method for extracting and correcting the effective area of palm veins effectively eliminates interference areas for subsequent palm vein recognition and eliminates the influence of palm angle issues on palm vein recognition.
[0094] This application also provides an identification method, which includes processing a palm vein image library and a palm vein image to be identified using the palm vein effective region extraction and correction method; and using a palm vein identification algorithm to identify and compare the processed palm vein image to be identified and the processed palm vein image library.
[0095] In this embodiment, the palm vein recognition algorithm can be any palm vein recognition method based on a deep learning network model. The palm vein effective region extraction and correction method is used to unify the palm vein image library and the palm vein image to be recognized, extracting the effective palm vein region in the palm vein image as much as possible to exclude interference regions other than the palm area, and unifying the palm orientation angle in the effective palm vein region to eliminate unnecessary interference regions and angles in the subsequent palm vein recognition process. This reduces the difficulty of palm vein recognition in the subsequent palm vein recognition algorithm and helps to improve recognition accuracy.
[0096] This application also provides a computer-readable storage medium for storing a computer program, which, when executed by a processor, implements the method for extracting and correcting the effective area of the palm vein.
[0097] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for extracting and correcting the effective area of palm veins, characterized in that, include: Obtain palm vein images; The rectangular effective area of the palm vein in the palm vein image is detected and four finger root points are located in the effective area of the palm vein. The four finger root points include point P1 between the root of the thumb and the root of the index finger, point P2 between the root of the index finger and the root of the middle finger, point P3 between the root of the middle finger and the root of the ring finger, and point P4 between the root of the ring finger and the root of the little finger. The steps for determining whether the effective area of the palmar vein belongs to the left or right hand based on the four finger base points include: Establish a two-dimensional rectangular coordinate system with key point P1 as the origin; calculate the deflection angle α of the lines connecting P2, P3, and P4 to P1 relative to the X-axis direction. n1 Where n∈(2,3,4); determine whether P2, P3, and P4 are located in the same quadrant of a two-dimensional rectangular coordinate system with the key point P1 as the origin; if so, determine the deflection angle α corresponding to P2, P3, and P4. 21 α 31 and α 41 To determine whether the effective area of the palmar vein belongs to the left or right hand; if not, select two key points P located in the same quadrant. i and P j According to P i and P j The corresponding deflection angle α i1 and α j1 To determine whether the effective area of the palmar vein belongs to the left or right hand, where i∈(2,3,4), j∈(2,3,4) and i<j; and The steps to adjust the effective area of the palm vein so that the fingers face upwards, and to perform orientational rotation correction on the effective area of the palm vein according to the structural characteristics of the left and right hands, so that the points between the bases of the index and middle fingers and between the bases of the little and ring fingers are on the same horizontal line parallel to the X-axis, include: selecting key points P2 and P4; for the palm veins of the right hand, calculating the orientational rotation angle β=arctan((y4'-y2') / (x4'-x2')); for the palm veins of the left hand, calculating the orientational rotation angle β=arctan((y2'-y4') / (x2'-x4')); if the orientational rotation angle β is greater than 0, then rotate the effective area of the palm vein counterclockwise around the image center point by angle β; if the orientational rotation angle β is less than 0, then rotate the effective area of the palm vein clockwise around the image center point by angle β; where x2' and y2' are the x and y coordinates of the second key point P2, respectively, and x4' and y4' are the y coordinates of the second key point P2. These are the x and y coordinates of the fourth key point P4, respectively.
2. The method for extracting and correcting the effective area of palm veins as described in claim 1, characterized in that, The four finger root points within the effective area of the palmar vein are located as follows: x n '= x n -x src ;and n '= and n -and src ; Where, x n 'and y n 'Locate the nth key point P respectively n x and y coordinates n and y n These are the nth key points P in the original palm vein image. n x and y coordinates; src and y src The x and y coordinates are the upper left corner of the effective area of the detected rectangular palmar vein.
3. The method for extracting and correcting the effective area of palm veins as described in claim 1, characterized in that, Based on the deflection angles α corresponding to P2, P3, and P4 21 α 31 and α 41 To determine whether the effective area of the palmar vein belongs to the left or right hand, specifically: If α 21 >α 31 >α 41 The effective area for palmar veins is from the left hand; If α 21 <α 31 <α 41 The effective area of the palmar vein comes from the right hand.
4. The method for extracting and correcting the effective area of palm veins as described in claim 1, characterized in that, According to P i and P j The corresponding deflection angle α i1 and α j1 To determine whether the effective area of the palmar vein belongs to the left or right hand, specifically: Calculate the deflection angle difference Δα = α i1 -α j1 ; If Δα > 0, then the effective area of the palmar vein originates from the left hand; If Δα < 0, then the effective area of the palmar vein comes from the right hand.
5. The method for extracting and correcting the effective area of palm veins as described in claim 1, characterized in that, α n1 = arctan((and n '-y1') / (x n '-x1')); Where, x n 'and y n 'These are the nth key points P' n The x and y coordinates are given by x1' and y1', respectively, which are the x and y coordinates of the first key point P1.
6. The method for extracting and correcting the effective area of palm veins as described in claim 5, characterized in that, After azimuth rotation correction of the effective area of the palm vein, the method for extracting and correcting the effective area of the palm vein further includes: Calculate the x-coordinate of key points P2 and P4 after rotation and their y-coordinate in the direction of the x-axis. Remove pixels in the effective area of the palm vein whose ordinate value is less than the ordinate value of the rotated keypoint P2, and / or remove pixels in the effective area of the palm vein whose ordinate value is less than the ordinate value of the rotated keypoint P4.
7. A method for identification, characterized in that, include: The palm vein image library and the palm vein image to be identified are processed using the palm vein effective region extraction and correction method as described in any one of claims 1 to 6. as well as A vein recognition algorithm is used to identify and compare the processed palm vein image to be identified with a processed palm vein image database.
8. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store a computer program, which, when executed by a processor, implements the palm vein effective area extraction and correction method according to any one of claims 1 to 6.