Measurement of camouflage performance is of fundamental importance for military stealth applications. The goal of camouflage assessment algorithms is to automatically assess the effectiveness of camouflage in agreement with human detection responses. We propose a new method for computational evaluation of camouflage effectiveness. We evaluate the performance of the new method and other existing algorithms in a comparative setting which utilised an extensive human visual experiment. The results show that the new method is correlated with the human target searching results with higher correlations than the existing algorithms.

In this paper, a new image authentication scheme based on quadtree segmentation is presented. In this scheme, partial digital signature encryption is employed to ascertain the origin of the image. Furthermore, the quadtree structure is imposed on the design of the authentication code. The authentication code consists of the quadtree list and the mean values of the quadtree leaf nodes. The size of the authentication code is adaptively determined according to the image characteristics. In the experiments, JPEG and JPEG20()0 lossy compression and malicious manipulations are employed to evaluate the validity of the proposed scheme. The experimental results show that this scheme permits some acceptable operations and can detect malicious manipulations. Furthermore, when a malicious manipulation is detected, the mean values of the quadtree leaf nodes can be applied to recover the manipulated areas.

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The article presents a novel fragile watermarking scheme based on the concept of pixel differencing for the integrity verification of digital images. The scheme uses the human visual system to embed the authentication data into the difference between the input pixel and the average of its neighbouring pixels. The new scheme is capable of outperforming others because it not only provides a securer, more efficient detecting procedure, but also offers better resultant image quality. To demonstrate how well the new scheme can work in detection ability and security, some experiments and security analyses are also included.