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  • 1. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 5, July 2012 DWT Based Copy-Move Image Forgery Detection Preeti Yadav ,Yogesh Rathore ,Aarti Yadu  II. LITERATURE REVIEW Abstract— In an age with digital media, it is no longer true that seeing is believing.In addition, digital forgeries, can be Since the key characteristics of Copy-Move forgery is indistinguishable from authentic photographs. In a copy-move that the copied part and the pasted part are in the same image, image forgery, a part of an image is copied and then pasted on a one method to detect this forgery is exhaustive search, but it different location within the same image .In this paper an is computationally complex and more time is needed for improved algorithm based on Discrete Wavelet Transform detection. A. C. Popescu and H. Farid proposed a similar (DWT)is used to detect such cloning forgery. In this technique detection method [2], in which the image blocks are reduced DWT (Discrete Wavelet Transform) is applied to the input image to yield a reduced dimensional representation.After that in dimension by using Principal Component Analysis (PCA). compressed image is divided into overlapping blocks. These But the efficiency of detection algorithm was not good, blocks are then sorted and duplicated blocks are identified. Due because, blocks are directly extracted from the original to DWT usage, detection is first carried out on lowest level image, resulting in a large number of blocks. D. Soukal, image representation so this Copy-Move detection process proposes DCT based copy-move forgery detection in a single increases accuracy of detection process. image, In which The image blocks are represented by quantized DCT (Discrete Cosine Transform) coefficients, Keywords- Digital Tempering,DWT Copy-Move forgery. and a lexicographic sort is adopted to detect the duplicated image blocks [3]. B.L.Shivakumar and Dr. S.Santhosh I INTRODUCTION Baboo have proposed copy-move forgery detection method Copy-Move forgery is performed with the intention to based on SURF, which detects duplication region withmake an object ―disappear‖ from the image by covering it with different size. Experimental result shows that the proposeda small block copied from another part of the same image[1]. method can detect copy-move forgery with minimum false match for images with high resolution[4] . To increase theUsually, such an image tampering is done with the aim of speed of operation process many researchers use blockingeither hiding some image details, in which case a background approaches [5]. G.Li, Q.Wu, D.Tu developed a sortedis duplicated, or adding more details. Whichever the case, neighborhood method based on DWT (Discrete Waveletimage integrity is lost.Because the copied segments come Transform) and SVD (Singular Value Decomposition) [6].Infrom the same image, the color palette, noise components, this method the computation of SVD takes lot of time and itdynamic range and the other properties will be compatible is computationally complex.with the rest of the image, thus it is very difficult for a humaneye to detect. Sometimes, even it makes harder for technology III. PROPOSED METHODto detect the forgery, if the image is retouched with the tools In this proposed method an image is scanned from thethat are available. upper left corner to the lower right corner while sliding a B×B block. The DWT transform is calculated For each block, the DWT coefficients are stored as one row in the matrix A. The matrix will have (M+B+1)(N–B+1) rows and B×B columns.The rows of A are lexicographically sorted . The DWT coefficients for each block are now being compared instead of the pixel representation, if two successive rows of the sorted matrix A are found, the algorithm stores the positions of the matching blocks in a separate list B,and increments a shift-vector counter C. For all normalized shift Figure 1. Example of Copy-Move forgery (a) original image vectors, the matching blocks that contributed to that specific (b) tampered image shift vector are colored with the same color and thus identified as segments that might have been copied and moved. The Proposed method of copy-move forgery detection has following main parts. Manuscript received July, 2012 1. Discrete Wavelet Transform Preeti Yadav:, Final year M-Tech CSE, CSVTU Bhilai,RITEE Raipur, 2. Lexicographic Sorting (e-mail:preetiyadu@yahoo.co.in).Raipur, India,Mobile-9827974272 3. Shift Vector Calculation Yogesh Rathore:, :, Department of CSE, CSVTU Bhilai,RITEE Raipur, 4. Neighbor block matching (e-mail:yogeshrathore23@gmail.com).Raipur, India,le-Mobi9301058533. Aarti Yadu, Department of IT, CSVTU Bhilai,RITEE Raipur, (e-mail:artiyadu@gmail.com).Raipur, India. 3.1 Discrete Wavelet Transform 56 All Rights Reserved © 2012 IJARCSEE
  • 2. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 5, July 2012 Wavelet decomposition of the images is used due to its s = (s1, s2) = (x1 – y1, x2 –y2).inherent multiresolution characteristics. The basic idea ofusing Discrete Wavelet Transform is to reduce the size of the Because the shift vectors –s and s correspond to the sameimage at each level, e.g., a square image of size 2j ×2j pixels at shift, the shift vectors s are normalized[9].level L reduces to size 2j/2 × 2j/2 pixels at level L+1. At eachlevel, the image is decomposed into four sub images. The sub The normalized shift vectors s(1),s(2), …, s(K), are thoseimages are labeled LL,LH, HL and HH, The notation LH, HL whose occurrence exceeds a user-specified threshold T:and HH correspond to the vertical, horizontal and diagonal C(s(g)) > T for all g = 1, …, K.components of the image respectively. LL corresponds to thecoarse level coefficients or the approximation image. This 3.4 Neighbor Shift Matchingimage(LL) is used for further decomposition.. These sub For a suspected pair of blocks, the system comparesimages can be combined together to restore the previous features of nearby blocks of both of the blocks of a pair whichimage which was decomposed. are at the same vector distance from the corresponding Below figure shows the image pyramid[7].Level-0 image is block.Neighbor Shift value is calculated by subtracting twoused for matching of blocks and then these matched blocks equivalent feature vectors. Shift vector of the entire suspectedare carried to the next higher level. Final match is performed duplicate region will be same. Two copied and then movedon the original image itself. areas will yield some pair of identical features. The same shift vector will be formed by this. For a particular number of neighbors this shift vector will be checked . Same shift vector will be showing the duplicated region. IV. EXPERIMENTAL RESULT (a) (b) (c) Figure 3. Forgery detection result (16*16)(a) original image(b) tampered image (c) detection result Figure 2. Image pyramid3.2 Lexicographic SortThe lexicographic or lexicographical order, (also known (a) (b) (c)as lexical order, dictionary order, alphabetical order orlexicographic(al) product), is a generalization of the way the Figure 4 Copy-Move Forgery detection result(48*48) (a) original image(b)alphabetical order of words is based on the alphabetical order tampered image (c) detection resultof letters. TABLE I. COMPARISIONWITH DIFFERENT SIZED COPY-MOVE An important property of the lexicographical order is that it IMAGE REGIONpreserves well-orders, that is, if I and J are well-ordered sets, Copy-Move Region Matchedthen the product set I ×J with the lexicographical order is also Image Size Region Accuracywell-ordered[8]. Size No of No of in % Pixels PixelsIn this step lexicographic sorting is performed on the rows of 256×256 16×16 256 256 100%matrix A. if two consecutive rows of the sorted matrix A are 256×256 48×48 2304 2208 96%found, the algorithm stores the positions of the identicalblocks in a separate list B and increments a shift-vectorcounter C. V. CONCLUSION In this paper an algorithm for detecting copy move forgery3.3 Shift Vector Calculation using Discrete Wavelet Transform (DWT) is proposed,.Our algorithm has lower computational complexity, since Let (x1, x2) and (y1, y2) be the positions of the two exhaustive search for identical blocks is performed only onmatching blocks. The shift vector s between the two the image at the lowest resolution. In future , I would like tomatching blocks is calculated as apply Principal Component Analysis, PCA, to the feature 57 All Rights Reserved © 2012 IJARCSEE
  • 3. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 5, July 2012vector to reduce its dimension, so time complexity will bereduced. The algorithm gave best performance for detectionof small size copy move forgery. Ms Arti Yadu has done B.E. in Information REFERENCES Technology from Chhatisgarh Swami Vivekanand University Bhilai,C.G..Her area of Interest is Artificial Intelligence and Network[1] B.L.Shivakumar,Lt. Dr. S.Santhosh Baboo ‖Detecting Copy-ove Forgery Security.in Digital Images: A Survey and Analysis of Current ethods ―Global Journalof Computer Science and Technology Vol. 10 Issue 7 Ver. 1.0 September2010[2] A.C.Popescu and H.Farid, ―Exposing digital forgeries by detectingduplicated image regions,‖ Dartmouth College, Hanover, New Hampshire,USA: TR2004-515, 2004.[3] J. Fridrich, D. Soukal, and J. Lukas, ―Detection of copymove forgery indigital images,‖ Proceedings of the Digital Forensic Research Workshop.Cleveland OH, USA, 2003[4] B.L.Shivakumar and Lt. Dr. S.Santhosh Baboo ―Detection of RegionDuplication Forgery in Digital Images Using SURF‖ IJCSI InternationalJournal of Computer Science Issues, Vol. 8, Issue 4, No 1, July 2011[5]Sarah A. Summers, Sarah C. Wahl ―Multimedia Security and ForensicsAuthentication of Digital images‖http: // cs.uccs.edu /~cs525/ studentproj/proj52006 / sasummer/doc/cs525projsummersWahl.doc[6] G.Li, Q.Wu, D.Tu, and Shaojie Sun, ―A sorted neighborhood approachfor detecting duplicated regions in image forgeries based on DWT andSVD,‖ IEEE International Conference on Multimedia & Expo, 2007. [7] Saiqa khan,Arun kulkarni“Reduced Time Complexity for Detection ofCopy-Move Forgery Using Discrete Wavelet Transform‖InternationalJournal of Computer Applications Volume 6– No.7, September 2010[8] Vivek Kumar Singh and R.C. Tripathi‖ Fast and Efficient RegionDuplication Detection in Digital Images Using Sub-Blocking Method―International Journal of Advanced Science and Technology Vol. 35,October, 2011.[9] Rafael C. Gonzalez, Richard E. Woods, Steven L.Eddins,―Digital ImageProcessing using MATLAB‖,Second Edition, Pearson Publications, 2004.[10] Preeti Yadav,Yogesh Rathore‖Detection of Copy-M ove Forgery ofImages Using DWT‖ International Journal on Computer Science andEngineering (IJCSE) Vol 4 April 2012. AUTHORS PROFILE Mrs Preeti Yadav is Assistant Professor inDepartment of Computer Science and Engineering at MM ollege ofTechnology, Raipur, C.G. ,India.she is Pursuing Masters degree(M-Tech 4thsemester) in Computer Science From Chhattisgarh swami vivekanandUniversity C.G.,India. Currently. Her research interest includes: ImageProcessing and Cryptography,Information Systems Security. Mr. Yogesh Rathore is a Sr. Lecturer in Department ofComputer Science and Engineering, Raipur Institute of Technology, Raipur(c.g.) . He is M-Tech in Computer Science .His area of interest includeDigital image processing & Computer Graphics. 58 All Rights Reserved © 2012 IJARCSEE

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