Copy-move forgery detection using multiresolution local binary patterns

https://doi.org/10.1016/j.forsciint.2013.04.023Get rights and content

Abstract

Copy-move forgery is one of the most popular tampering artifacts in digital images. In this paper, we present an efficient method for copy-move forgery detection using Multiresolution Local Binary Patterns (MLBP). The proposed method is robust to geometric distortions and illumination variations of duplicated regions. Furthermore, the proposed block-based method recovers parameters of the geometric transformations. First, the image is divided into overlapping blocks and feature vectors for each block are extracted using LBP operators. The feature vectors are sorted based on lexicographical order. Duplicated image blocks are determined in the block matching step using k-d tree for more time reduction. Finally, in order to both determine the parameters of geometric transformations and remove the possible false matches, RANSAC (RANdom SAmple Consensus) algorithm is used. Experimental results show that the proposed approach is able to precisely detect duplicated regions even after distortions such as rotation, scaling, JPEG compression, blurring and noise adding.

Introduction

Digital images play an important role in our daily lives due to their flexibility. But they are susceptible to malicious activities. According to Ref. [1], even in 1989, almost 10% of all color photographs published in United States has been altered and forged. This is mainly due to advent of low-cost hardware and sophisticated photo-editing software which alleviate digital images manipulation. Professional forgers with advanced technology often leave no trail on forged images. This trend decreases credibility of digital images which are presented in scientific journals, news items, medical record, and financial documents. Therefore, it is necessary to create new tools and techniques to discover the authenticity and integrity of digital images.

Several methods have recently been proposed to detect image forgeries: watermarking-based schemes [2], [3], perceptual hash-based schemes [4], and digital image forensic-based schemes [5], [6]. In the first group, the watermark information and ownership identification is embedded imperceptibly into the digital image. With the assumption that tampering will alter a watermark, an image can be authenticated by verifying the extracted watermark. However, this method has some significant limitations: (1) the watermark must be inserted at the time of recording where is often unavailable in practical applications, (2) this method can only be used for watermarked images and (3) the information embedding operation degrades image quality. In the second method, the perceptual hash function generates a hash value from the original image and it is stored by the authenticator. In the authentication process, a new hash value is computed from a suspected image and compared with the stored one to detect a forgery. Unlike watermarking methods, the hash-based schemes do not change the image quality but generation hash value during taking a photo is not always possible in practical applications. In contrast to the first two groups, digital image forensics techniques work in the absence of any digital watermark or signature. In the third category, the intrinsic features focusing on inconsistency and similarities in the image are extracted. Core of these techniques is appropriate features extraction which depends on the type of image forgery.

Copy-move forgery is one of the most popular tampering artifacts where a part of an image is copied and pasted to another part of the same image, with the aim of adding or hiding an object. Since duplicated regions come from the same image, they have similar properties like noise, color and texture. On the other hand, a forger can easily modify the geometry of the copied part, add noise, or compress the resulting image. So, a copy-move forgery detection technique should be robust to rotation, scaling, blurring, noise and compression.

In this paper, we propose a copy-move forgery system based on Multiresolution Local Binary Patterns (MLBP). This method is not only able to precisely detect the altered area, but also robust against rotation, scaling, JPEG compression, blurring and noise adding. In this approach, RANSAC (RANdom SAmple Consensus) algorithm is used to remove the false matches and estimate the geometric transformation parameters with high reliability. The rest of the paper is organized as follows. In Section 2, the related works on copy-move forgery detection are introduced. Section 3 briefly introduces LBP and its extensions. In Section 4, the proposed algorithm is presented. In Section 5, several experiments are performed for forensic analysis. Discussion and comparison with other methods are presented in Section 6. Finally, the conclusion is drawn in Section 7.

Section snippets

Related works

Many techniques have been proposed to address the problem of copy-move forgery detection. Block-based matching is one of the main methods for this purpose. First, the image is divided into overlapping blocks and then a feature extraction process is applied to represent the image blocks. In this step, the biggest challenge is to determine the features which yield the same or very similar values for duplicated blocks, even under various modifications. Since the similar regions would have similar

Local binary patterns (LBP) and its extensions

Among the feature descriptors, Local Binary Patterns (LBP) is one of the most famous and powerful ones. It has gained increasing attention in many image analyses applications due to its low computational complexity, invariance to monotonic gray-scale changes and texture description ability [20]. In practice, the LBP operator combines characteristics of statistical and structural texture analysis: it describes the texture with micro-primitives, often called textons, and their statistical

The proposed algorithm

In this section, details of the proposed method for duplicated and distorted region detection are presented. There are three main steps in our algorithm: feature extraction, block matching, and estimation of the geometric transformation parameters and remove the false matches. Fig. 3 shows the block diagram for our copy-move forgery detection scheme.

Experimental results

In this section, we first introduce experimental setup and evaluation metrics. Then, in the next section results of our algorithm are compared with two other methods which are based on SIFT [17] and DCT [8] descriptors. The former method is a feature-based technique, while the later technique is block-based.

Discussion and comparison with other methods

Experiments on the test images undergone post-processing operations such as scaling, JPEG compression, Gaussian blurring and AWGN show that the MLBP features can withstand these operations and allow forgery identification. Although duplicated regions with rotation through limited angles can accurately be detected.

The results in the Table 1 indicate that size of copied region and also type and number of MLBP operators has very small effect on average detection accuracy when no perturbation is

Conclusion

In this paper an efficient forensic method based on Multiresolution Local Binary Patterns (MLBP) for detecting copy-move forgery in digital images was proposed. The method does not need digital watermarks, signatures information or any metadata. The proposed method not only detects duplicated regions but determines the geometric transformations applied to the forged regions. Experimental results demonstrated that the proposed approach could even detect duplicated regions with common

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