CN109544474A - A kind of enhancement method of fingerprint image based on phase stretching conversion - Google Patents
A kind of enhancement method of fingerprint image based on phase stretching conversion Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 17
- 230000002708 enhancing effect Effects 0.000 claims abstract description 22
- 238000012545 processing Methods 0.000 claims description 7
- 230000003044 adaptive effect Effects 0.000 claims description 6
- 230000000877 morphologic effect Effects 0.000 claims description 6
- 230000010339 dilation Effects 0.000 claims description 3
- 230000003628 erosive effect Effects 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 3
- 230000007547 defect Effects 0.000 abstract 1
- 238000005516 engineering process Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 3
- 238000011160 research Methods 0.000 description 3
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- 230000003014 reinforcing effect Effects 0.000 description 1
- 210000001525 retina Anatomy 0.000 description 1
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Classifications
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T5/00—Image enhancement or restoration
- G06T5/70—Denoising; Smoothing
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T5/00—Image enhancement or restoration
- G06T5/90—Dynamic range modification of images or parts thereof
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/1347—Preprocessing; Feature extraction
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/20—Special algorithmic details
- G06T2207/20021—Dividing image into blocks, subimages or windows
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/20—Special algorithmic details
- G06T2207/20036—Morphological image processing
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/20—Special algorithmic details
- G06T2207/20048—Transform domain processing
- G06T2207/20056—Discrete and fast Fourier transform, [DFT, FFT]
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/20—Special algorithmic details
- G06T2207/20172—Image enhancement details
- G06T2207/20182—Noise reduction or smoothing in the temporal domain; Spatio-temporal filtering
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Abstract
The present invention effectively enhances defect existing for aspect for calculating speed in fingerprint recognition and texture, propose a kind of Enhancement Method of fingerprint image in fingerprint recognition system, this method utilizes the fingerprint image interception target fingerprint image got, then overall contrast enhancing is carried out to target fingerprint image using limitation contrast histogram equalization method, and enhanced target fingerprint image is obtained into enhanced fingerprint image using the method progress texture enhancing of phase stretching conversion and to background denoising.The present invention can effectively enhance the fingerprint texture information in fingerprint picture especially low quality fingerprint picture, to improve the performance of fingerprint recognition in fingerprint recognition system.
Description
Technical field
The invention belongs to field of image processings, more specifically, are related to a kind of method of Fingerprint enhancement.
Background technique
With the continuous development of information age, biological identification technology is increasingly valued by people.Bio-identification skill
Art is that the technology of identity is proved using biological inherent feature identification, and bio-identification can be independent of various artificial overages
Carry out itself of reference, and research has shown that, everyone fingerprint, iris, retina etc. are different from others, and
It is constant throughout one's life, therefore bio-identification has stronger reliability.Currently, the living body feature for discriminating one's identification mainly includes referring to
Line, sound, iris, DNA etc..
Fingerprint identification technology is one of most widely used technology in biometrics identification technology, is widely used in various bodies
In part verifying and identification.Fingerprint recognition has the characteristics that fingerprint acquisition device is simple, system is small, it is fast to identify speed, thus is easy to
It is realized in kinds of platform.Facilitating for fingerprint obtains and there is uniqueness fingerprint to be made to become people's second generation identity card suggestion packet
The identity information contained.At present about the algorithm of fingerprint identification technology there are many kinds of, there is more Automatic FingerprintVerification
The product and research achievement of system, but still certain specific application requirements cannot be reached, so fingerprint is classified always automatically is
The focus and difficult point project of experts and scholars' research.Fingerprint recognition system can get finger by contact or non-contacting mode
Print image, by the identity information for determining the fingerprint to fingerprint image automatic recognition classification.The crucial portion of fingerprint identification technology
Dividing mainly includes these three aspects of fingerprint pretreatment, feature extraction and fingerprint matching, wherein the reinforcing effect pair of fingerprint pretreatment
It is had very important effect in subsequent match identification.
Quality of the performance of Automated Fingerprint Identification System dependent on input fingerprint image, the fingerprint quality difference of input is current
The a great problem that Automated Fingerprint Identification System faces.Fingerprint Enhancement Algorithm mainly utilizes image processing techniques to remove fingerprint
Various noise jammings in image, the texture information of prominent fingerprint, make its being more clear of texture structure, thus obtain one it is good
Good fingerprint image.Fingerprint Image Enhancement exactly be directed to fingerprint recognition system it is low to low-quality fingerprint picture recognition performance this
The solution that problem proposes, and then guarantee the accuracy and reliability of feature extraction and fingerprint matching.Fingerprint enhancement
Pre-processing of the method as fingerprint recognition needs quickly and effectively, it is easy to accomplish and fingerprint texture information needs effectively enhancing.
The method of fingerprint enhancing at present has very much, but still has greatly improved space in terms of the effectively enhancing of calculating speed and texture.
Summary of the invention
In view of the above-mentioned problems, the purpose of the present invention is to provide a kind of easy to operate, Fingerprint enhancements for being easily achieved
Algorithm particularly relates to the lower position of print image intermediate-resolution to the fingerprint image that fingerprint recognition system obtains and carries out texture information
Enhancing, improves the performance of fingerprint recognition in system of fingerprints, and this method can effectively enhance fingerprint picture especially low quality fingerprint
Fingerprint texture information in picture, to improve the performance of fingerprint recognition in fingerprint recognition system.
The present invention proposes that technical solution is as follows:
A kind of enhancement method of fingerprint image based on phase stretching conversion, which comprises the steps of:
Step 1: the target area in fingerprint image being obtained using adaptive threshold, that is, includes the figure of finger print information part
Picture；
Step 2: whole right using limitation contrast histogram equalization method progress to the target fingerprint image got
It is handled than degree enhancing；
Step 3: enhanced fingerprint image enhances the texture information of fingerprint using phase stretching conversion method,
And remove the noise in background.
Optionally, the step 1 specifically comprises the following steps:
Step 1-1 carries out adaptive thresholding to fingerprint image, obtains the binary map of fingerprint image；
Step 1-2 eliminates fingerprint texture and the noise of background area in bianry image using morphology opening operation, first to figure
Morphological dilations are carried out again as carrying out morphological erosion operation, eliminate the interference noise region of fingerprint texture and background area, most
Big connected region is the juncture area of fingerprint and background, finally obtains the boundary rectangle in largest connected region, and intercept fingerprint
The image of the rectangle frame position can be obtained target fingerprint image in image.
Optionally, in step 2, when limiting contrast histogram equalization, will need the image that enhances be divided into it is multiple just
Square sub-block carries out histogram equalization processing to each sub-block respectively.The size and target fingerprint picture traverse of the sub-block
Ratio be set as 1/16.
Further, the phase stretching conversion method in the step 3 specifically comprises the following steps:
Enhanced fingerprint image is transformed into frequency domain by Fourier transformation by 3-1；
3-2 calculates the angle value of each pixel in frequency domain, the angle value of each pixel is multiplied by non-linear frequency phase
The factor is closed, result figure is calculated；
3-3, the above results figure, which is transformed into time domain by inverse Fourier transform, can be obtained enhanced fingerprint texture letter
Breath.
Optionally, the noise in the removal background in the step 3 will be lower than maximum gradation value 5% in fingerprint target image
Gray value of the position in the enhanced image result of fingerprint texture of pixel be set as 0.
It is especially the beneficial effects of the present invention are: the enhancement method of fingerprint image can quickly and effectively enhance fingerprint picture
The fingerprint texture information of the unintelligible position of fingerprint picture middle finger line, calculation amount is small, and effect is obvious, can be in fingerprint recognition system
Fingerprint recognition provides a kind of effective Enhancement Method.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
It obtains other drawings based on these drawings.
Fig. 1 is a kind of flow chart of the Fingerprint Image Enhancement based on phase stretching conversion of the method for the present invention
Fig. 2 (a)-(c) is the procedure chart that target fingerprint image is obtained in the method for the present invention
Fig. 3 (a)-(b) is the enhancing result figure using limitation contrast histogram equalization method to target fingerprint image
Fig. 4 (a)-(c) is for fingerprint texture information enhancement and to the result figure after background removal noise in enhancing result
Specific embodiment
To make the object, technical solutions and advantages of the present invention clearer, the present invention is done further with reference to the accompanying drawing
Ground detailed description.
As shown in Figure 1, a kind of enhancement method of fingerprint image based on phase stretching conversion proposed by the present invention, technical solution
It is as follows:
1) fingerprint image is inputted
2) target fingerprint region is obtained
As shown in Fig. 2 (a), adaptive thresholding is carried out to fingerprint image first, obtains the binary map of fingerprint image, threshold
Value is using the average value of neighborhood territory pixel, and each pixel is compared with the average value of its field pixel, greater than average
Value takes 0, otherwise takes 255；As shown in Fig. 2 (b)-(c), carry out morphology opening operation, morphology opening operation be first to image into
The operation of row morphological erosion carries out morphological dilations again, eliminates the interference noise region of fingerprint texture and background area, most Dalian
Logical region is the juncture area of fingerprint and background；The boundary rectangle in largest connected region is finally obtained, and intercepts fingerprint image
In the image of the rectangle frame position can be obtained target fingerprint image.
3) dimensional parameters are calculated
As shown in Fig. 2 (c), according to the finger-print region image of interception, the dimensional parameters of the image of the acquisition are calculated, in case
After use.
4) adaptive threshold enhancing is handled
It is target fingerprint image as shown in Fig. 3 (a), Fig. 3 (b) is enhanced target fingerprint image.Due to of poor quality
Fingerprint image greatly the reason is that causing fingerprint image contrast poor since uneven illumination is even or whole fingerprint image
As unintelligible, carrying out overall contrast enhancing to target fingerprint image facilitates the further enhancing to fingerprint texture information.It adopts
Enhancing processing, the limitation contrast are carried out to the overall contrast of target fingerprint image with limitation contrast histogram equalization
Histogram equalization is that the image that will need to enhance is divided into multiple square sub blocks, and it is equal to carry out histogram to each sub-block respectively
Weighing apparatusization processing.
Since the fingerprint image size that different fingerprint recognition systems are got is different, the target fingerprint picture size got
Also it is not fixed, to make overall contrast Enhancement Method have more robustness, the ratio for choosing 1/16 is standard, i.e.,
Wherein, A is the sub-block size for limiting contrast histogram enhancement image, the width of W target fingerprint image.According to acquisition
The target fingerprint image arrived determines the size for dividing enhancing sub-block, size round numbers part in the result of calculating.
5) the fingerprint texture information of enhanced target fingerprint image is further enhanced
The texture information of fingerprint contains the key message of fingerprint and the base of fingerprint uniqueness in fingerprint recognition system
Plinth directly influences the accuracy of fingerprint differentiation.This method carries out fingerprint texture information using phase stretching conversion enhancing algorithm
Enhancing, as shown in Fig. 4 (a)-(b), specific calculating process are as follows: first by enhanced fingerprint image pass through Fourier transformation turn
Change to frequency domain；Then the angle value for calculating each pixel in frequency domain, is multiplied by non-linear frequency for the angle value of each pixel
Correlation factor calculates result figure；Then the above results figure is transformed into time domain by inverse Fourier transform again can be obtained increasing
Fingerprint texture information after strong.
6) and the noise in background, the fingerprint image enhanced are removed
As shown in Fig. 4 (c), for the effect picture of the noise in removal background after texture enhancing, wherein it is in rectangle frame
Position in the unsharp position of finger print information and corresponding enhancing result, by comparative result figure it can be found that one in fingerprint image
It is visually not easy the texture information observed a bit, which may be implemented effectively to enhance.
Calculating process are as follows:
Wherein, x, y are the coordinate in image, and out (x, y) is the fingerprint image of output, and input (x, y) is the finger of input
Image after the enhancing of line texture information, original (x, y) are target fingerprint image, and max [] is to obtain maximum value, the i.e. operation
Purpose is by the position in fingerprint target image lower than the pixel of maximum gradation value 5% in the enhanced image knot of fingerprint texture
Gray value in fruit is set as 0, can be obtained final fingerprint enhancing figure.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all in essence of the invention
Made any modifications, equivalent replacements, and improvements etc., should all be included in the protection scope of the present invention within mind and principle.
Claims (6)
1. a kind of enhancement method of fingerprint image based on phase stretching conversion, which comprises the steps of:
Step 1: the target area in fingerprint image being obtained using adaptive threshold, that is, includes the image of finger print information part；
Step 2: overall contrast is carried out using limitation contrast histogram equalization method to the target fingerprint image got
Enhancing processing；
Step 3: enhanced fingerprint image enhancing the texture information of fingerprint using phase stretching conversion method, and goes
Except the noise in background.
2. the enhancement method of fingerprint image according to claim 1 based on phase stretching conversion, which is characterized in that the step
Rapid 1 specifically comprises the following steps:
Step 1-1 carries out adaptive thresholding to fingerprint image, obtains the binary map of fingerprint image；
Step 1-2, using morphology opening operation eliminate bianry image in fingerprint texture and the noise of background area, first to image into
The operation of row morphological erosion carries out morphological dilations again, eliminates the interference noise region of fingerprint texture and background area, most Dalian
Logical region is the juncture area of fingerprint and background, finally obtains the boundary rectangle in largest connected region, and intercepts fingerprint image
In the image of the rectangle frame position can be obtained target fingerprint image.
3. the enhancement method of fingerprint image according to claim 1 or 2 based on phase stretching conversion, it is characterised in that: institute
When stating step 2 limitation contrast histogram equalization, the image enhanced will be needed to be divided into multiple square sub blocks, respectively to every
A sub-block carries out histogram equalization processing.
4. the enhancement method of fingerprint image according to claim 3 based on phase stretching conversion, it is characterised in that:
The size of the sub-block and the ratio of target fingerprint picture traverse are set as 1/16.
5. the enhancement method of fingerprint image according to claim 3 based on phase stretching conversion, which is characterized in that the step
Phase stretching conversion method in rapid 3 specifically comprises the following steps:
Enhanced fingerprint image is transformed into frequency domain by Fourier transformation by 3-1；
3-2, calculate frequency domain in each pixel angle value, by the angle value of each pixel be multiplied by non-linear frequency correlation because
Son calculates result figure；
3-3, the above results figure, which is transformed into time domain by inverse Fourier transform, can be obtained enhanced fingerprint texture information.
6. the enhancement method of fingerprint image according to claim 5 based on phase stretching conversion, it is characterised in that: the step
The noise in removal background in rapid 3 will be lower than the position of the pixel of maximum gradation value 5% in fingerprint in fingerprint target image
Gray value in the enhanced image result of texture is set as 0.
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Cited By (7)
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| CN110348425A (en) * | 2019-07-19 | 2019-10-18 | 北京迈格威科技有限公司 | Go the method, apparatus, equipment and computer readable storage medium of shading |
| CN110443307A (en) * | 2019-08-06 | 2019-11-12 | 平顶山学院 | It is a kind of that the theoretical image interfusion method with HSI transformation is stretched based on phase |
| CN110728201A (en) * | 2019-09-20 | 2020-01-24 | 南京元初科技有限公司 | Image processing method and device for fingerprint identification |
| CN111898512A (en) * | 2020-07-23 | 2020-11-06 | 杭州萤石软件有限公司 | Fingerprint identification method and device |
| CN112241935A (en) * | 2019-07-18 | 2021-01-19 | 杭州海康威视数字技术股份有限公司 | Image processing method, device and equipment and storage medium |
| CN112329497A (en) * | 2019-07-18 | 2021-02-05 | 杭州海康威视数字技术股份有限公司 | Target identification method, device and equipment |
| CN112861649A (en) * | 2021-01-19 | 2021-05-28 | 平安科技（深圳）有限公司 | Fingerprint signature generation method and device, electronic equipment and computer storage medium |
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| CN112241935A (en) * | 2019-07-18 | 2021-01-19 | 杭州海康威视数字技术股份有限公司 | Image processing method, device and equipment and storage medium |
| CN112329497A (en) * | 2019-07-18 | 2021-02-05 | 杭州海康威视数字技术股份有限公司 | Target identification method, device and equipment |
| CN112241935B (en) * | 2019-07-18 | 2023-05-26 | 杭州海康威视数字技术股份有限公司 | Image processing method, device and equipment and storage medium |
| CN110348425A (en) * | 2019-07-19 | 2019-10-18 | 北京迈格威科技有限公司 | Go the method, apparatus, equipment and computer readable storage medium of shading |
| CN110443307A (en) * | 2019-08-06 | 2019-11-12 | 平顶山学院 | It is a kind of that the theoretical image interfusion method with HSI transformation is stretched based on phase |
| CN110443307B (en) * | 2019-08-06 | 2024-01-12 | 平顶山学院 | Image fusion method based on phase stretching theory and HSI transformation |
| CN110728201A (en) * | 2019-09-20 | 2020-01-24 | 南京元初科技有限公司 | Image processing method and device for fingerprint identification |
| CN110728201B (en) * | 2019-09-20 | 2023-04-07 | 南京元初科技有限公司 | Image processing method and device for fingerprint identification |
| CN111898512A (en) * | 2020-07-23 | 2020-11-06 | 杭州萤石软件有限公司 | Fingerprint identification method and device |
| CN112861649A (en) * | 2021-01-19 | 2021-05-28 | 平安科技（深圳）有限公司 | Fingerprint signature generation method and device, electronic equipment and computer storage medium |
| CN112861649B (en) * | 2021-01-19 | 2024-05-10 | 平安科技（深圳）有限公司 | Fingerprint signature generation method and device, electronic equipment and computer storage medium |
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