CN100337244C - Method of oblique wavelet image fingerprint extraction and authentication - Google Patents

Abstract

The present invention relates to a method of an oblique wavelet image fingerprint extraction and identifying method which discloses an image fingerprint extracting method and an image fingerprint identifying method. An oblique wavelet algorithm has excellent compressing performance and reducing performance for images, and thus, the oblique wavelet algorithm is particularly suitable for the extraction of image fingerprints. The defects of the poor robustness of the transformation of visual invariability and the poor robustness of geometric transformation in the prior art are overcome. The prevent invention has the following procedures: an image is transformed into a plurality of grey square image blocks. A wave filter is used for filtering the image blocks in rows and lines according to a convolution equation. Grey result values after the filtration of the image blocks in a triangle area positioned in the left upper part in a result value matrix are read and are arranged into a sequence. Positive values in the sequence correspond to bit 1, negative values in the sequence correspond to bit 0, and thus, the image fingerprint of the entire image is formed. The identifying method of the image fingerprint is that the xor operation is provided for the binary number on the position corresponding to two image fingerprints. The sameness is determined according to the reference quantity of 1 value.

Description

The extraction of oblique wavelet image fingerprint and verification method

Technical field:

The present invention relates to a kind of extracting method of finger image, the invention still further relates to the verification method of finger image.

Background technology:

In recent years, along with network technology and rapid development of multimedia, people can utilize digital device making, processing and memory image easily and utilize the internet transmission image.Yet digital image information very easily is copied, distorts and propagates privately, has caused the safety problem of digital picture thus.In addition; when digital picture is browsed and is chosen by client as commodity; the user need find own interested commodity fast by certain approach; the image publisher also needs these commercial digital pictures are effectively managed; make it can satisfy browsing, search for and classifying of image, can monitor effectively and protect again oneself product in case by pirate, distort.People expect, if can make every width of cloth image have unique sign, this sign both can make a distinction self and other image effectively, the content characteristic that can reflect image self again, make operation to picture material (as browse, search for, classify, checking, anti-tamper detection etc.) become possibility, make digital picture obtain a sign of getting up, as the fingerprint that carries out human identity identification with himself content association.The finger image technology obtains the characteristic information of piece image by certain feature extraction algorithm, because the finger image technology links together the characteristic information of the exclusive content of each width of cloth image and its acquisition, the different images information that takes on a different character, this is corresponding with the fingerprint of oneself as everyone.This emerging technology just is called as the finger image technology, and the characteristic information that image is obtained through this technical finesse calls " fingerprint " of image visually.Finger image need satisfy two kinds of performances: 1, robustness; Finger image should have unchangeability to the image transformation of maintenance vision unchangeability such as lossy compression method, or the change that takes place must limit in allowed limits; 2, the property distinguished; For content tampering or the different image of two width of cloth, should be able to detect and distinguish difference according to the finger image that extracts.Image fingerprint extracting method was proposed by Schneider and Chang first in 1996, they utilize the intensity histogram of variable-sized image block, with the histogram average as finger image, this method depends on image intensity, when image carried out low-pass filtering or image saved as the JPEG compressed file of low-quality coefficient, this method had just lost practicality.After this various image fingerprint extracting method of Ti Chuing, though be improved to a certain extent, but under the prerequisite that keeps susceptibility, these methods can't be to all vision invariant mappings, as diminish compression, low-pass filtering, sharpening and geometric transformation such as convergent-divergent, shearing etc. and keep robustnesss, particularly geometric transformation, the fingerprint of these methods to extracting through the image after the geometric transformation, its robustness reduces greatly.

General oblique wavelet transformation (slantlet transform) method is proposed in 1998 first by Selesnick, I.W.Selesnick, The slantlet transform, Proceedings Of the IEEE-SP Int.Symp.on Time-Frequency and Time-Scale Analysis, pp.53-56, Pittsburgh, October 6-9,1998. (IEEE signal Processing forum, about the 53rd to 56 page of the paper of time frequency analysis, on October 6th to 9,1998, Pittsburgh) and in 1999 oblique wavelet transformation has been done the more elaboration of system.I.W.Selesnick, The slantlet transform, IEEE Trans on SignalProcessing, vol 47, no 5, pp.1304-1313, May 1999. (IEEE signal Processing periodical, May in 1999 the 47th volume fifth phase 1304-1313 page or leaf) this wavelet transformation demonstrates in being applied to data compression than traditional discrete cosine transform and the better compression performance of other wavelet transformations, can be referring to following article.G.Panda，P.K.Dash，A.K.Pradhan，and?S.K.Meher，″Data?compression?of?powerquality?events?using?the?slantlet?transform，″IEEE?Trans.Power?Delivery，vol.17，no.2，pp.662-667，April?2002.。(use the data compression of the power events of wavelet transformation, IEEE signal Processing periodical, April in 2002 the 17th volume 662-667 page or leaf) the finger image algorithm can utilize the powerful compression performance of oblique wavelet transformation to extract more brief finger image from image, guarantee enhanced robust simultaneously, and keep hypersensitivity.But, also occur at present oblique method of wavelet is applied to the technical scheme of going in the finger image treatment technology.

Summary of the invention:

The extracting method that the purpose of this invention is to provide a kind of oblique wavelet image fingerprint is to overcome the defective of existing image fingerprint extracting method to the poor robustness of vision invariant mapping and geometric transformation.The present invention realizes by following steps: one, the image with fingerprint to be extracted is converted into length and the equal gray level image of width; Two, gray level image is divided into from left to right, from top to bottom the foursquare image block of several same size, total number of image block is m * m, and m is necessary for 2 power; Three, ask for the wave filter that is used for oblique wavelet transformation, the coefficient of this wave filter selects eight, is respectively g (0), g (1), g (2), g (3), g (4), g (5), g (6) and g (7), and the coefficient of wave filter is obtained as follows: ${\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="C20051001027400091.png"\; state="\{\{state\}\}">s</figure-callout>}}_1=6*\sqrt{m/((m^2-1)*(4*m^2-1))};$ ${\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="C20051001027400091.png"\; state="\{\{state\}\}">t</figure-callout>}}_1=2*\sqrt{3/(m*(m^2-1))};$ s ₀=(1) * s ₁* (m-1)/2; t ₀=((m+1) * s ₁/ 3-m*t ₁) * (m-1)/(2*m); G (0)=(s ₀+ t ₀)/2; G (1)=(s ₀-t ₀)/2; G (2)=(s ₁+ t ₁)/2; G (3)=(s ₁-t ₁)/2; G (4)=g (1)+g (3) * (m-1); G (5)=(1) * g (3); G (6)=g (0)+g (2) * (m-1); G (7)=(1) * g (2); Four, use the wave filter try to achieve on gray level image earlier by row to each image block by the filtering of convolution formula, and then by being listed as each image block by the filtering of convolution formula, gray scale end value after a filtering is obtained in the position of each image block, the gray scale end value is formed an end value matrix after all filtering; Be like this operation to each image block by the filtering of convolution formula in this step: the gray-scale value of this image block multiply by respectively ask behind g (0), g (1), g (2), g (3), g (4), g (5), g (6) and the g (7) all products and, just obtain end value after the filtering of this image block except that m again.Five, gray scale end value after the filtering of each image block that is arranged in the upper left half part Delta Region of end value matrix diagonal line is read be arranged into a sequence in order; Six, with the positive corresponding bit " 1 " in the gray scale end value after the filtering that reads out, negative value corresponding bit " 0 " forms the two-value fingerprint sequence that only has " 0 " and " 1 ", has just formed the finger image of entire image.Method of the present invention is implemented the purpose of oblique wavelet transformation, the signal low frequency part to be focused on the signal front portion exactly, and the signal HFS is focused on the rear portion, in fact most of energy of signal all concentrates on the low frequency part of signal, therefore through only extracting the purpose that the signal low frequency part just can reach compression and extract finger image behind the oblique wavelet transformation.Digital picture belongs to 2D signal, through twice oblique wavelet transformation of row and column, the low frequency part of picture signal focuses on the upper left corner of image, and HFS focuses on the lower right corner of image, and the extraction work of finger image has just been finished in the conversion of extracting the signal of low frequency part and finishing the bi-level digital sequence.Because tiltedly wavelet algorithm has good compression performance and reducing property to image, the utmost point is applicable to the extraction of finger image, exactly because its compression performance is good, also helps it and in lossy compression method, low-pass filtering, sharpening and geometric transformation such as processes such as convergent-divergent, shearing, keep robustness and susceptibility.Reasonable in design, the reliable operation of method of the present invention has bigger promotional value.

The present invention also provides the verification method of oblique wavelet image fingerprint, and it is realized by following step: A, extract the finger image of original image and the finger image of image to be verified respectively; B, the bi-level digital of two finger image correspondence positions is done exclusive-OR operation, export the as a result sequence identical with finger image length; C, the number of " 1 " value has just drawn the difference degree β of two finger images divided by the length of sequence as a result in the sequence as a result; D, judge whether that β is less than pre-set threshold θ; E, result judge then that for not two width of cloth picture materials there are differences; G, result are for being to judge that then two width of cloth picture materials are identical.After method of the present invention is asked for the difference degree of two finger images,, represent that then two width of cloth picture materials are identical if this difference is 0; If this difference is 1, represent that then two width of cloth picture materials are different fully.In actual applications, this difference often between 0 and 1, then preestablishes a threshold value θ, when difference greater than θ, think that there is significant difference in two width of cloth picture materials; Otherwise think that two width of cloth picture materials are basic identical.

Oblique wavelet image fingerprint extraction and verification method are based on the characteristics of finger image technology, promptly need not image is changed, this is the basic difference with the digital figure watermark technology, it can be applied to the demanding occasion of picture quality, typical occasion such as medical image, military map, mapping, these images are not allow a bit to revise, also just can't embed digital watermark.Such as medical image, may cause the offset of histoorgan to a bit trickle change of picture material, cause diagnosis and treatment to make a mistake; And for the military and civilian map, the slight change of picture material can cause measured deviation on map, and this is unallowed.

Description of drawings:

Fig. 1 is the step synoptic diagram of embodiment of the present invention one, and Fig. 2 is the step synoptic diagram of embodiment two; Fig. 3 is the synoptic diagram that embodiment three carries out the scanning of " it " font, and Fig. 4 to Fig. 7 is the schematic diagram of image comparison in the embodiment two.

Embodiment:

Embodiment one: specify present embodiment below in conjunction with Fig. 1.Present embodiment is realized by following steps: one, the image with fingerprint to be extracted is converted into length and the equal gray level image of width; Two, gray level image is divided into from left to right, from top to bottom the foursquare image block of several same size, total number of image block is m * m, and m is necessary for 2 power; Three, ask for the wave filter that is used for oblique wavelet transformation, the coefficient of this wave filter selects eight, is respectively g (0), g (1), g (2), g (3), g (4), g (5), g (6) and g (7), and the coefficient of wave filter is obtained as follows: ${\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="C20051001027400091.png"\; state="\{\{state\}\}">s</figure-callout>}}_1=6*\sqrt{m/((m^2-1)*(4*m^2-1))};$ ${\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="C20051001027400091.png"\; state="\{\{state\}\}">t</figure-callout>}}_1=2*\sqrt{3/(m*(m^2-1))};$ s ₀=(1) * s ₁* (m-1)/2; t ₀=((m+1) * s ₁/ 3-m*t ₁) * (m-1)/(2*m); G (0)=(s ₀+ t ₀)/2; G (1)=(s ₀-t ₀)/2; G (2)=(s ₁+ t ₁)/2; G (3)=(s ₁-t ₁)/2; G (4)=g (1)+g (3) * (m-1); G (5)=(1) * g (3); G (6)=g (0)+g (2) * (m-1); G (7)=(1) * g (2); Four, use the wave filter try to achieve on gray level image earlier by row to each image block by the filtering of convolution formula, handle lastrow and handle next line again, and then by being listed as each image block by the filtering of convolution formula, handle the first from left row and handle right row again, gray scale end value after a filtering is obtained in the position of each image block, the gray scale end value is formed an end value matrix after all filtering; Five, gray scale end value after the filtering of each image block that is arranged in the upper left half part Delta Region of end value matrix diagonal line is read be arranged into a sequence in order; Six, with the positive corresponding bit " 1 " in the gray scale end value after the filtering that reads out, negative value corresponding bit " 0 " forms the two-value fingerprint sequence that only has " 0 " and " 1 ", has just formed the finger image of entire image.In step 4, is like this operation to each image block by the filtering of convolution formula: the gray-scale value of image block multiply by respectively ask behind g (0), g (1), g (2), g (3), g (4), g (5), g (6) and the g (7) all products and, just obtain end value after the filtering of this image block except that m again.

Embodiment two: specify present embodiment below in conjunction with Fig. 2.Present embodiment is realized by following steps: A, extract the finger image of original image and the finger image of image to be verified respectively; B, the bi-level digital of two finger image correspondence positions is done exclusive-OR operation, export the as a result sequence identical with finger image length; C, the number of " 1 " value has just drawn the difference degree β of two finger images divided by the length of sequence as a result in the sequence as a result; D, judge whether that β is less than pre-set threshold θ; E, result judge then that for not two width of cloth picture materials there are differences; F, result are for being to judge that then two width of cloth picture materials are identical.Be the finger image demonstration example of oblique wavelet transformation below, Fig. 4 is a width of cloth original image, and Fig. 5 is the image after Fig. 4 process JPEG lossy compression method, is essentially identical on this two width of cloth image vision obviously.After this two width of cloth image passed through oblique wavelet image fingerprint extraction respectively, it was 0.0020 that two fingerprint comparisons are obtained fingerprint difference, approaches 0, showed this two width of cloth picture material much at one.Fig. 6 and Fig. 7 are the visually diverse images of two width of cloth, pass through oblique wavelet image fingerprint extraction respectively after, fingerprint comparison difference is 0.5254, approaches 1, shows that this two width of cloth picture material is different.Threshold value θ can be chosen near two mid points between the distance, and for example 0.3.

Embodiment three: specify present embodiment below in conjunction with Fig. 3.The difference of present embodiment and embodiment one is: in the following order gray scale end value after the filtering of image block is read in step 5 and be arranged into a sequence: spiral from the upper left corner " it " font of end value matrix and tortuously read the gray scale end value to the lower right.Because the low frequency part of gray image signals concentrates on the left and the top of end value matrix, and frequency increases gradually to the lower right, reads numerical frequency according to present embodiment and changes gently, and compression performance is better.Digital number among Fig. 3 is exactly a scanning sequency, and corresponding affiliated frequency range preferably selects 0 to 33 low frequency part as picture signal to read into a sequence in the present embodiment.Other step is identical with embodiment one.

Embodiment four: the difference of present embodiment and embodiment one is: increase following steps between step 1 and step 2: gray level image is done scale handle, the result that scale is handled obtains long and the wide image that is respectively former gray level image 1/2.Other step is identical with embodiment one.So operation, because image has dwindled, the scanning errors that image might occur when the equipment of this method is used in input is reduced by corresponding, and the influence of subsequent processing steps is also become very small.Other step is identical with embodiment one.

Embodiment five: the difference of present embodiment and embodiment one is: increase following steps between step 1 and step 2: gray level image is done wavelet transform process, wavelet transform process is that gray level image is made a sub-band division, gets the low frequency sub-band image as result.Can use any one small echo in the wavelet transform process, before tiltedly small echo is handled, earlier image be carried out a filtering, can further improve the compressibility and the robustness of signal.Other step is identical with embodiment one.

Claims (5)

1, the extracting method of oblique wavelet image fingerprint is characterized in that it realizes by following steps: one, the image of fingerprint to be extracted is converted into the gray level image that length and width equate; Two, gray level image is divided into from left to right, from top to bottom the foursquare image block of several same size, total number of image block is m * m, and m is necessary for 2 power; Three, ask for the wave filter that is used for oblique wavelet transformation, the coefficient of this wave filter selects eight, is respectively g (0), g (1), g (2), g (3), g (4), g (5), g (6) and g (7), and the coefficient of wave filter is obtained as follows: $s_1=6*\sqrt{m/((m^2-1)*(4*m^2-1))};$

$t_1=2*\sqrt{3/(m*(m^2-1))};$ s ₀=(1) * s ₁* (m-1)/2; t ₀=((m+1) * s ₁/ 3-m*t ₁) * (m-1)/(2*m); G (0)=(s ₀+ t ₀)/2; G (1)=(s ₀-t ₀)/2; G (2)=(s ₁+ t ₁)/2; G (3)=(s ₁-t ₁)/2; G (4)=g (1)+g (3) * (m-1); G (5)=(1) * g (3); G (6)=g (0)+g (2) * (m-1); G (7)=(1) * g (2); Four, use the wave filter try to achieve on gray level image earlier by row to each image block by the filtering of convolution formula, and then by being listed as each image block by the filtering of convolution formula, gray scale end value after a filtering is obtained in the position of each image block, the gray scale end value is formed an end value matrix after all filtering; Be like this operation to each image block by the filtering of convolution formula in this step: the gray-scale value of this image block multiply by respectively ask behind g (0), g (1), g (2), g (3), g (4), g (5), g (6) and the g (7) all products and, just obtain end value after the filtering of this image block except that m again; Five, gray scale end value after the filtering of each image block that is arranged in the upper left half part Delta Region of end value matrix diagonal line is read be arranged into a sequence in order; Six, with the positive corresponding bit " 1 " in the gray scale end value after the filtering that reads out, negative value corresponding bit " 0 " forms the two-value fingerprint sequence that only has " 0 " and " 1 ", has just formed the finger image of entire image.

2, the extracting method of oblique wavelet image fingerprint according to claim 1 is characterized in that in the following order gray scale end value after the filtering of image block being read in step 5 and is arranged into a sequence: spiral from the upper left corner " it " font of end value matrix and tortuously read the gray scale end value to the lower right.

3, the extracting method of oblique wavelet image fingerprint according to claim 1, it is characterized in that increasing between step 1 and step 2 following steps: gray level image is done scale handle, the result that scale is handled obtains long and the wide image that is respectively former gray level image 1/2.

4, the extracting method of oblique wavelet image fingerprint according to claim 1, it is characterized in that between step 1 and step 2, increasing following steps: gray level image is done wavelet transform process, wavelet transform process is that gray level image is made a sub-band division, gets the low frequency sub-band image as result.

5, a kind of verification method of oblique wavelet image fingerprint of the extracting method that has adopted the described oblique wavelet image fingerprint of claim 1 is characterized in that it is realized by following steps: A, extract the finger image of original image and the finger image of image to be verified respectively; B, the bi-level digital of two finger image correspondence positions is done exclusive-OR operation, export the as a result sequence identical with finger image length; C, the number of " 1 " value has just drawn the difference degree β of two finger images divided by the length of sequence as a result in the sequence as a result; D, judge whether that β is less than pre-set threshold θ; E, result judge then that for not two width of cloth picture materials there are differences; F, result are for being to judge that then two width of cloth picture materials are identical.

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