Very fast watermarking by reversible contrast mapping

Reversible contrast mapping (RCM) is a simple integer transform that applies to pairs of pixels. For some pairs of pixels, RCM is invertible, even if the least significant bits (LSBs) of the transformed pixels are lost. The data space occupied by the LSBs is suitable for data hiding. The embedded information bit-rates of the proposed spatial domain reversible watermarking scheme are close to the highest bit-rates reported so far. The scheme does not need additional data compression, and, in terms of mathematical complexity, it appears to be the lowest complexity one proposed up to now. A very fast lookup table implementation is proposed. Robustness against cropping can be ensured as well

On the Use of Normalized Compression Distances for Image Similarity Detection

his paper investigates the usefulness of the normalized compression distance (NCD) for image similarity detection. Instead of the direct NCD between images, the paper considers the correlation between NCD based feature vectors extracted for each image. The vectors are derived by computing the NCD between the original image and sequences of translated (rotated) versions. Feature vectors for simple transforms (circular translations on horizontal, vertical, diagonal directions and rotations around image center) and several standard compressors are generated and tested in a very simple experiment of similarity detection between the original image and two filtered versions (median and moving average). The promising vector configurations (geometric transform, lossless compressor) are further tested for similarity detection on the 24 images of the Kodak set subject to some common image processing. While the direct computation of NCD fails to detect image similarity even in the case of simple median and moving average filtering in 3 × 3 windows, for certain transforms and compressors, the proposed approach appears to provide robustness at similarity detection against smoothing, lossy compression, contrast enhancement, noise addition and some robustness against geometrical transforms (scaling, cropping and rotation

Stéganographie d'images basées sur le théorème chinois des restes

- Dans ce papier nous nous intéressons au problème de cacher dans une image, moyennant une seule opération, de multiple messages provenant de multiples utilisateurs. L'idée est d'utiliser le théorème chinois des restes. Sur le plan théorique, il est établi qu'un nombre illimité de messages peuvent être insérée dans l'image elle-même. Une des limites de l'approche vient du fait que ces multiples messages ne doivent être ni détectables, ni visibles. Par construction, la première condition est naturellement satisfaite, par contre toute la difficulté consiste à satisfaire la seconde condition. Un atout de cette approche est que chaque utilisateur peut disposer d'une clé différente pour détecter une des marques superposée à l'image

High Capacity Reversible Watermarking

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Distortion Control Reversible Watermarking

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Mapping Based Reversible Watermarking

International audienceThe set of pairs of pixels is partitioned into disjoint groups of equal number of pairs. Furthermore, a subset of pairs of pixels is selected and each pair is uniquely associated with a group of the partition. If the size of the groups is m, log2m bits of data can be embedded into an image pair by replacing it by the pairs of a group. As long as at detection one can find if a pair was replaced or not, the transform is reversible. Hence a reversible watermarking scheme is obtained by embedding together with the watermark the information needed to locate the transformed pairs. The paper discusses how to select the subset of pixel pairs and the partition in order to obtain high capacity watermarking schemes. It is also shown that a recently proposed reversible scheme is based on this principle. Due to its flexibility, the general scheme is expected to introduce less distortion. The experimental results obtained so far are promising

Morphological Residual Representations of Signals

. A general approach for residual representation of 1D and 2D signals is defined. Signals are reconstructed as a sum of components that are recursively determined by using a constructive transform. Several morphological constructive transforms are proposed and their corresponding representations are discussed. The use of residual representations in signal and image compression is investigated with promising results. 1 Introduction A problem of considerable concern in signal/image processing and analysis is the representation of the data in terms of meaningful geometrical patterns that are characterized by shape and size. The shape-size relation is reflected by the scale concept. The nonlinear approach (based on mathematical morphology) for multiscale representation is strongly advocated in [1]; scale is defined as the smallest size of a shape pattern (generated by a prototype pattern of unit size) that can "fit" inside the signal. This paper proposes a general framework for 1D and 2D ..

Distortion-free robust watermarking: a case study

International audienceThis paper investigates the distortion-free robust watermarking by multiple marking. Robust watermarking is first performed. Then, by reversible watermarking, the information needed to invert both the robust and the reversible watermarking is embedded. In case of no attacks, the robust watermark is detected and the authorized party exactly recovers the original. In case of attacks, one can suppose that the robust watermark can still be detected, but the reversibility is lost. The approach relies on the embedded capacity of the reversible watermarking. The overall scheme inherits the robustness of the ?rst marking stage. The selection of the robust and of the reversible watermarking schemes is discussed. In order to improve the robustness of the first marking stage against the second one a joint marking procedure is proposed. A case study of reversible watermarking providing very good robustness against JPEG compression is presented

Simple Reversible Watermarking Schemes: Further Results

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