Ahmad Mahmoudi-Aznaveh

Bio: Ahmad Mahmoudi-Aznaveh is an academic researcher from Shahid Beheshti University. The author has contributed to research in topics: Image quality & Feature (machine learning). The author has an hindex of 6, co-authored 21 publications receiving 289 citations.

Iterative Copy-Move Forgery Detection Based on a New Interest Point Detector

Abstract: In this paper, we propose a novel copy-move forgery detection scheme that can accurately localize duplicated regions with a reasonable computational cost. To this end, a new interest point detector is proposed utilizing the advantages of both block-based and traditional keypoint-based methods. The detected keypoints adaptively cover the entire image, even low contrast regions, based on a uniqueness metric. Moreover, a new filtering algorithm is employed, which can effectively prune the falsely matched regions. Considering the new interest point detector, an iterative improvement strategy is proposed. The whole procedure is iterated along with adjusting the keypoints density based on the achieved information. The experimental results demonstrate that the proposed scheme outperforms the state-of-the-art methods using two public benchmark databases.

Adaptive matching for copy-move Forgery detection

Abstract: The objective of copy-move forgery detection methods are to find copied regions within the same image. There are two main approaches to detect copy-move forgery: keypoint-based and block-based methods. Although the former is superior in terms of computational complexity, these methods neglect the smooth regions since they confine their search to salient points. On the other hand, while block-based methods consider smooth areas, they introduce a huge number of false matches. In this paper, it is proposed to employ an adaptive threshold in the matching phase in order to overcome this problem. The experimental results demonstrate that the proposed method can greatly reduce the number of false matches which results in improving both performance and computational cost.

Image quality measurement besides distortion type classifying

Abstract: To identify the distortion type and quantify the quality of images, a new method is presented based on a comparison among the structural properties as well as consideration of the luminance characteristics of the two compared images. To fulfill this aim, the mathematical concept of the singular value decomposition (SVD) theorem has been applied. The difference vector of the reflection coefficients of the disturbed and the original image on the right singular vector matrix of the original image are considered. Many tests were conducted to evaluate the performance, using a widespread subjective study involving 779 images from the Live Image Quality Assessment Database, Release 2005. The results showed a greatly improved performance along with the ability to distinguish distortion type of images.

A correlation based feature representation for first-person activity recognition

Abstract: In this paper, a simple yet efficient activity recognition method for first-person video is introduced. The proposed method is appropriate for the representation of high-dimensional features such as those extracted from convolutional neural networks (CNNs). The per-frame (per-segment) extracted features are considered as a set of time series, and inter and intra-time series relations are employed to represent the video descriptors. To find the inter-time relations, the series are grouped and the linear correlation between each pair of groups is calculated. The relations between them can represent the scene dynamics and local motions. The introduced grouping strategy helps to considerably reduce the computational cost. Furthermore, we split the series in the temporal direction in order to preserve long term motions and better focus on each local time window. In order to extract the cyclic motion patterns, which can be considered as primary components of various activities, intra-time series correlations are exploited. The representation method results in highly discriminative features which can be linearly classified. The experiments confirm that our method outperforms the state-of-the-art methods in recognizing first-person activities on the three challenging first-person datasets.

A bibliography of pixel-based blind image forgery detection techniques

Abstract: With the advent of powerful image editing tools, manipulating images and changing their content is becoming a trivial task. Now, you can add, change or delete significant information from an image, without leaving any visible signs of such tampering. With more than several millions pictures uploaded daily to the net, the move towards paperless workplaces, and the introduction of e-Government services everywhere, it is becoming important to develop robust detection methods to identify image tampering operations and validate the credibility of digital images. This led to major research efforts in image forensics for security applications with focus on image forgery detection and authentication. The study of such detection techniques is the main focus of this paper. In particular, we provide a comprehensive survey of different forgery detection techniques, complementing the limitations of existing reviews in the literature. The survey covers image copy-move forgery, splicing, forgery due to resampling, and the newly introduced class of algorithms, namely image retouching. We particularly discuss in detail the class of pixel-based techniques which are the most commonly used approaches, as these do not require any a priori information about the type of tampering. The paper can be seen as a major attempt to provide an up-to-date overview of the research work carried in this all-important field of multimedia. HighlightsA new comprehensive survey of pixel-based forgery detection methods is presented.A framework for grouping different forgery detection algorithms is described.We outline the strengths and weaknesses of research efforts in forgery detection.Numerous tables and figures, analyzing existing algorithms, are discussed.An extensive list of references covering the work of the last decade is provided.

SVD-Based Quality Metric for Image and Video Using Machine Learning

Abstract: We study the use of machine learning for visual quality evaluation with comprehensive singular value decomposition (SVD)-based visual features. In this paper, the two-stage process and the relevant work in the existing visual quality metrics are first introduced followed by an in-depth analysis of SVD for visual quality assessment. Singular values and vectors form the selected features for visual quality assessment. Machine learning is then used for the feature pooling process and demonstrated to be effective. This is to address the limitations of the existing pooling techniques, like simple summation, averaging, Minkowski summation, etc., which tend to be ad hoc. We advocate machine learning for feature pooling because it is more systematic and data driven. The experiments show that the proposed method outperforms the eight existing relevant schemes. Extensive analysis and cross validation are performed with ten publicly available databases (eight for images with a total of 4042 test images and two for video with a total of 228 videos). We use all publicly accessible software and databases in this study, as well as making our own software public, to facilitate comparison in future research.

Fast and Effective Image Copy-Move Forgery Detection via Hierarchical Feature Point Matching

Abstract: Copy-move forgery is one of the most commonly used manipulations for tampering digital images. Keypoint-based detection methods have been reported to be very effective in revealing copy-move evidence due to their robustness against various attacks, such as large-scale geometric transformations. However, these methods fail to handle the cases when copy-move forgeries only involve small or smooth regions, where the number of keypoints is very limited. To tackle this challenge, we propose a fast and effective copy-move forgery detection algorithm through hierarchical feature point matching. We first show that it is possible to generate a sufficient number of keypoints that exist even in small or smooth regions by lowering the contrast threshold and rescaling the input image. We then develop a novel hierarchical matching strategy to solve the keypoint matching problems over a massive number of keypoints. To reduce the false alarm rate and accurately localize the tampered regions, we further propose a novel iterative localization technique by exploiting the robustness properties (including the dominant orientation and the scale information) and the color information of each keypoint. Extensive experimental results are provided to demonstrate the superior performance of our proposed scheme in terms of both efficiency and accuracy.