Application of wavelet-cosine transform to image compression

International audienceA two-dimensional discrete transform which is a composition of the wavelet and the cosine transform is presented and applied to image compression. The usefulness of the 2-D wavelet and wavelet-cosine transform for the lossy compression is compared. Independently of which transform was used, the nonuniform quantization distinctly increased the efficiency of lossy compression

Lossless and Lossy Minimal Redundancy Pyramidal Decomposition for Scalable Image Compression Technique

International audienceWe present a new scalable compression technique dealing simultaneously with both lossy and lossless image coding. An original DPCM scheme with refined context is introduced through a pyramidal decomposition adapted to the LAR (Locally Adaptive Resolution) method, which becomes by this way fully progressive. An implicit context modeling of the prediction errors, due to the low resolution image representation including variable block size structure, is then exploited to the for lossless compression purpose

Embedding Multilevel Image Encryption in the LAR Codec

International audienceA still image codec should not only to be good from compression point of view, it might also provide services. The LAR interleaved S+P codec allows lossless to lossy coding, presenting both resolution and distortion scalability. The proposed method brings image encryption at no cost in the LAR framework. It exploits the embedded quadtree decomposition of the LAR to provide multilevel protection to the whole bit-stream. Theoretical aspects are considered and experimental results show the effectiveness of the process

Joint Lossless Coding and Reversible Data Embedding in a Multiresolution Still Image Coder

International audienceModern still image codecs furnish more than just good distortion-rate performances. They must also provide some services. Scalability in resolution and quality, error resilience and embedded bitstreams were among the first one to be available. There is still room for enhancement, especially when it comes to security-oriented features. Data embedding is necessary, as for inserting metadata, or to copyright a picture. We present the use of a very simple reversible data embedding method in a multiresolution still image codec framework. Experimental results show the usefulness of such an adequation of techniques from different domain. Moreover, the embedding overhead is evaluated and shows to be very acceptable

Joint Lossless Coding and Reversible Data Embedding in a Multiresolution Still Image Coder

International audienceModern still image codecs furnish more than just good distortion-rate performances. They must also provide some services. Scalability in resolution and quality, error resilience and embedded bitstreams were among the first one to be available. There is still room for enhancement, especially when it comes to security-oriented features. Data embedding is necessary, as for inserting metadata, or to copyright a picture. We present the use of a very simple reversible data embedding method in a multiresolution still image codec framework. Experimental results show the usefulness of such an adequation of techniques from different domain. Moreover, the embedding overhead is evaluated and shows to be very acceptable

Interleaved S+P Pyramidal Decomposition with Refined Prediction Model

International audienceScalability and others functionalities such as the Region of Interest encoding become essential properties of an efficient image coding scheme. Within the framework of lossless compression techniques, S+P and CALIC represent the state-of-the-art. The proposed Interleaved S+P algorithm outperforms these method while providing the desired properties. Based on the LAR (Locally Adaptive Resolution) method, an original pyramidal decomposition combined with a DPCM scheme is elaborated. This solution uses the S-transform in such a manner that a refined prediction context is available for each estimation steps. The image coding is done in two main steps, so that the first one supplies a LAR low-resolution image of good visual quality, and the second one allows a lossless reconstruction. The method exploits an implicit context modelling, intrinsic property of our content-based quad-tree like representation

Lossless and Lossy Minimal Redundancy Pyramidal Decomposition for Scalable Image Compression Technique

International audienceWe present a new scalable compression technique dealing simultaneously with both lossy and lossless image coding. An original DPCM scheme with refined context is introduced through a pyramidal decomposition adapted to the LAR (Locally Adaptive Resolution) method, which becomes by this way fully progressive. An implicit context modeling of the prediction errors, due to the low resolution image representation including variable block size structure, is then exploited to the for lossless compression purpose

La RWHT+P pour un codage multirésolution sans perte avancé

Cet article présente une méthode complète de codage sans perte multirésolution, à forte scalabilité sémantique. En particulier, une forme réversible de la classique Transformée de Walsh Hadamard (RWHT) est tout d'abord introduite comme alternative aux transformées sans perte standard. Une représentation pyramidale et des schémas de décomposition reposant sur cette transformée sont ensuite proposés pour un codage multirésolution réversible. Des améliorations significatives y sont apportées en ajoutant deux concepts supplémentaires : la ``résolution localement adaptative'' à travers une représentation quadtree, et une étape de prédiction. Les résultats expérimentaux montrent en final que la méthode RWHT+P proposée aboutit à d'excellentes performances comparées à celles de l'état de l'art

Fast recursive grayscale morphology operators: from the algorithm to the pipeline architecture

International audienceThis paper presents a new algorithm for an efficient computation of morphological operations for gray images and its specific hardware. The method is based on a new recursive morphological decomposition method of 8-convex structuring elements by only causal two-pixel structuring elements (2PSE). Whatever the element size, erosion or/and dilation can then be performed during a unique raster-like image scan involving a fixed reduced analysis neighborhood. The resulting process offers low computation complexity combined with easy description of the element form. The dedicated hardware is generic and fully regular, built from elementary interconnected stages. It has been synthesized into an FPGA and achieves high frequency performances for any shape and size of structuring element

One-pass Bitrate Control for MPEG-4 Scalable Video Coding using rho-domain

International audienceThis paper presents an attractive rate control scheme for the new MPEG-4 Scalable Video Coding standard. Our scheme enables us to control the bitrate at the output of the encoder on each video layer with great accuracy. Each frame is encoded only once, so that the computational complexity of the whole scheme is very low. The three spatial, temporal and quality scalabilities are handled correctly, as well as inter layer prediction and hierarchical B frames. A linear bitrate model is used to predict the output bitrate for a frame, based on a simple and effective framework called rho-domain. A coding-complexity measure is also introduced to dispatch the available bits among the frames, in order to reach a constant quality throughout the encoded video stream. To attest the performances of our rate control scheme, we present comprehensive results on some representative scalable video set-ups