Tampering detection methods based on image hashing have been widely studied with continuous advancements. However, most existing models cannot generate object-level tampering localization results, because the forensic hashes attached to the image lack contour information. In this paper, we present a novel tampering detection model that can generate an accurate, object-level tampering localization result. First, an adaptive image segmentation method is proposed to segment the image into closed regions based on strong edges. Then, the color and position features of the closed regions are extracted as a forensic hash. Furthermore, a geometric invariant tampering localization model named image alignment-based multi-region matching (IAMRM) is proposed to establish the region correspondence between the received and forensic images by exploiting their intrinsic structure information. The model estimates the parameters of geometric transformations via a robust image alignment method based on triangle similarity; in addition, it matches multiple regions simultaneously by utilizing manifold ranking based on different graph structures and features. Experimental results demonstrate that the proposed IAMRM is a promising method for object-level tampering detection compared with the state-of-the-art methods.

The block-based analysis for tamper localization is a prevailing mechanism in hash-based forgery detection algorithm. One of the main problems with a block-based analysis is its rough localization stemming from the demand to use relatively large blocks to reduce hash length. While decreasing the block size can improve the localization resolution, the hash length tends to become too long to be practical. In this paper, we propose a binary ranking hashing approach that satisfies both the requirements of compact hash length and small block size, to obtain a binary map combined with spatial information. Meanwhile, we investigate a multiscale difference map fusion approach that fuses multiple candidate difference maps, resulting from the analysis of the subtraction between two binary maps with different sliding windows, to obtain a single, more reliable tampering map with better localization resolution. We use manifold ranking to model this multiscale difference map fusion problem and propose a two-stage scheme, namely, ranking with tampering queries and nontampering queries. Our results indicate that the proposed tamper detection method can improve the tamper localization resolution compared with state-of-the-art methods.

Image-hashing-based tampering detection methods have been widely studied with continuous advancements. However, most of existing models are designed for a specific tampering. In this paper, we propose a novel quaternion-based image hashing to detect almost all types of tampering, including color changing, copy move, splicing, and so on. First, the quaternion Fourier-Mellin transform is used to calculate the geometric hash to eliminate the influence of geometric distortions. Then, a new quaternion image construction method, which combines advantages of both color and structural features, is proposed to implement the quaternion Fourier transform to calculate the image feature hash to locate the tampered regions. The objective is to provide a reasonably short image hashing with good performance, i.e., being perceptually robust against various content-preserving attacks while capable of detecting and locating almost all types of tampering. Furthermore, an adaptive tampering localization algorithm is proposed based on clustering analysis to improve the detection accuracy. The experimental results show that the proposed tampering detection model outperforms the existing state-of-the-art models and is very robust against various content-preserving attacks.