Multiresolution multiresource progressive image transmission

This paper presents a new progressive image transmission (PIT) design algorithm in which the resolution and resources (rate or distortion and storage size) at each transmission stage are allowed to be prespecified. This algorithm uses the wavelet transform and tree-structured vector quantizer (TSVQ) techniques. The wavelet transform is used to obtain a pyramid structure representation of an image. The vector quantizer technique is used to design a TSVQ for each subimage so that all the subimages that constitute the image at the current stage can be successively refined according to the resources available at that stage. The resources assigned to each subimage for the successive refinement is determined to optimize the performance at the current stage under the resource constraints. Normally, the resource constraints at each stage are determined by the specification of the transmission time or distortion for image data and the storage complexity of the TSVQ. The resolution at each stage is determined/specified according to the application or as part of the design process to optimize the visual effect.     

Reversible data-hiding for progressive image transmission

This research presents a multi-resolution reversible data-hiding algorithm to enable multi-scale marked images that are transmitted progressively to be exactly recovered at the receiver side once hidden data has been extracted. Based on the spatially hierarchical multi-layer structures of progressive-image transmission, the proposed algorithm first decimates the incoming image pixels into a pre-specified number of hierarchical layers of pixels. Then, it modifies pixel values in each hierarchical layer by shifting the interpolated-difference-values histogram between two neighboring layers of pixels to embed secret information into the corresponding hierarchical layer images. The proposed algorithm offers a reversible data-hiding ability for applications that use progressive image transmission to render progressive-image authentication, information-tagging, covert communications, etc. With progressive-reversible data-hiding, users of progressive image transmission can receive each original progressive image and complete hidden messages related to the received progressive image. This allows users to make real-time definite decisions according to an application's requirements. In contrast to other reversible data-hiding schemes, the algorithm proposed in this study features reversible data-hiding in progressive-image transmission based on a hierarchical decimation and interpolation technique. The interpolating process is used to reduce the difference values between the target pixel values in one progressive layer and their interpolated ones. This increases the hiding capacity of interpolation-differences histogram shifting. The experimental results demonstrate that the proposed method provides a greater embedding capacity and maintains marked images at a higher quality. Moreover, the proposed method has a low computational complexity as it requires only simple arithmetic computations.     

Human visual weighted quantization : a unified approach for subband and pyramidal image coders

In the field of the coding of digital video signals, the concept of hierarchical coding is of real interest. Decorrelation operators fulfilling that hierarchical requirement are subband operators and pyramidal systems. The aim of this paper is show that the same methodology can be used to solve the quantization problem in subband and pyramidal coders. The criterion considered here takes into account the eye sensitivity to spatial frequencies. An analytical approach is presented in that paper for the cases of fixed bit allocation and quantizer followed by an entropy coder.     

Entropy criterion for progressive Laplacian pyramid-based image transmission

Progressive image transmission under interactive user control is quite effective for low-bit-rate channels. The efficiency increases when significant details are transmitted first. A new criterion to extract them is presented, based on an entropy function which takes into account the features at different levels of a Laplacian pyramid. Results are compared with those given by existing algorithms.<>     

Real-time unequal error protection algorithms for progressive image transmission

We consider unequal error protection strategies for the efficient progressive transmission of embedded image codes over noisy channels. In progressive transmission, the reconstruction quality is important not only at the target transmission rate but also at the intermediate rates. An adequate error protection strategy may, thus, consist of optimizing the average performance over the set of intermediate rates. The performance can be the expected number of correctly decoded source bits or the expected distortion. For the rate-based performance, we prove some interesting properties of an optimal solution and give an optimal linear-time algorithm to compute it. For the distortion-based performance, we propose an efficient linear-time local search algorithm. For a binary symmetric channel, two state-of-the-art source coders (SPIHT and JPEG2000), we compare the progressive ability of our proposed solutions to that of the strategies that optimize the end-to-end performance of the system. Experimental results showed that the proposed solutions had a slightly worse performance at the target transmission rate and a better performance at most of the intermediate rates, especially at the lowest ones.     

基于视觉特性和小波分解的数字水印隐藏方法

本文提出了一种隐藏数字水印的新方法,该方法所隐藏的不是传统的序列码或比特流,而是将水印作为一幅二值图像来处理;并结合人眼视觉模型（ＨＶＳ）和图像的ＤＷＴ多尺度分解来隐藏水印。实验表明这种新方法在降低原始图像变换后视觉失真和提取的被隐藏水印图像失真两方面都达到较好的效果,鲁棒性也较好,这是一种很有发展前景的数字水印隐藏新方法。     

A weighted full-reference image quality assessment based on visual saliency

In full reference image quality assessment (IQA), the images without distortion are usually employed as reference, while the structures in both reference images and distorted images are ignored and all pixels are equally treated. In addition, the role of human visual system (HVS) is not taken account into subjective IQA metric. In this paper, a weighted full-reference image quality metric is proposed, where a weight imposed on each pixel indicates its importance in IQA. Furthermore, the weights can be estimated via visual saliency computation, which can approximate the subjective IQA via exploiting the HVS. In the experiments, the proposed metric is compared with several objective IQA metrics on LIVE release 2 and TID 2008 database. The results demonstrate that SROCC and PLCC of the proposed metric are 0.9647 and 0.9721, respectively,which are higher than other methods and it only takes 427.5 s, which is lower than that of most other methods.     

On the unequal error protection for progressive image transmission.

In this paper, we consider the unequal error protection (UEP) for progressive image transmission when the coded packet size is fixed. First, we prove that, for the source code with convex rate-distortion (R-D) function and practically used channel codes, the channel code rate for each packet in the optimal rate allocation is nondecreasing indeed. Then, we give an upper bound for the channel code rate of the last packet so that the number of rate allocations in the exhaustive search can be predicted. Further, we propose a heuristic optimization method which has low complexity and obtains performance approaching to the optimal solutions for various channel conditions and transmission rates.     

Reversible decorrelation method for progressive transmission of 3-Dmedical image

In this paper, the authors present a new reversible decorrelation method of three-dimensional (3-D) medical images for progressive transmission. Progressive transmission of an image permits gradual improvement of image quality while being displayed. When the amount of image data is very large, as a 3-D medical image, the progressive transmission plays an important role in viewing or browsing the image. The data structure presented in this paper takes account of interframe correlation as well as intraframe correlation of the 3-D image. This type of data structure has been termed the 3-D hierarchy embedded differential image (3-D-HEDI) as was derived from the earlier HEDI structure (Kim et al., 1995). Experiments were conducted to verify the performance of 3-D HEDI in terms of the decorrelation efficiency as well as the progressive transmission efficiency. It is compared with those of conventional hierarchy interpolation (HINT), two-dimensional (2-D) HEDI and differential pulse code modulation (DPCM). Experimental results indicate that 3-D HEDI outperforms HINT, 2-D HEDI and DPCM in both decorrelation efficiency as well as the progressive transmission efficiency on 3-D medical images     

A novel method for progressive image transmission using blocked wavelets

The techniques of progressive image transmission (PIT) divide image delivery into several phases. PIT's main objective is to efficiently and effectively provide an approximate reconstruction of the original image in each phase. Therefore, this study proposes the blocked wavelet progressive image transmission (BWPIT) method based on the wavelet transformation and the spatial similarity of pixels, to reduce the bit-rate and increase the image quality in an early phase of PIT. Experimental results show that the transmission bit-rate and the image quality of BWPIT are significantly better than those of bit-plane method (BPM), improved bit-plane method (IBPM), and wavelet-based progressive image transmission (WbPIT) method in each early phase.     

Error protection for progressive image transmission over memorylessand fading channels

Product channel codes are proposed to protect progressively compressed and packetized images for noisy channels. Within packets, the product code uses the concatenation of a rate-compatible punctured convolutional code and an error detecting parity check code. Across packets, Reed-Solomon codes are used. Benefits include flexible choice of delay, adaptability of error protection level (i.e., unequal error protection), and scalable decoding complexity. The system outperforms the best known image coders for memoryless channels and performs well on fading channels     

Penalized weighted least-squares image reconstruction for dual energy X-ray transmission tomography

We present a dual-energy (DE) transmission computed tomography (CT) reconstruction method. It is statistically motivated and features nonnegativity constraints in the density domain. A penalized weighted least squares (PWLS) objective function has been chosen to handle the non-Poisson noise added by amorphous silicon (aSi:H) detectors. A Gauss-Seidel algorithm has been used to minimize the objective function. The behavior of the method in terms of bias/standard deviation tradeoff has been compared to that of a DE method that is based on filtered back projection (FBP). The advantages of the DE PWLS method are largest for high noise and/or low flux cases. Qualitative results suggest this as well. Also, the reconstructed images of an object with opaque regions are presented. Possible applications of the method are: attenuation correction for positron emission tomography (PET) images, various quantitative computed tomography (QCT) methods such as bone mineral densitometry (BMD), and the removal of metal streak artifacts.     

基于人眼视觉特性的ROI渐进编码算法

一般基于感兴趣区域(ROI)的图像编码算法都没有充分考虑人眼视觉特性,在分析了JPEG2000中感兴趣区域编码的优缺点后,利用小波变换的特点并结合人眼视觉的掩蔽效应,提出了一种改进的ROI图像编码算法。首先将图像小波域中的所有低频系数进行移位处理,而对于小波域中的高频系数,仅对其属于ROI区域的系数进行移位处理,再利用等级树集合分割(SPIHT)算法进行编码传输。仿真实验证明了该算法比原有算法的图像主观质量更好。     

基于OFDM的改进的小波包图像传输

首先提出了一种新的基于OFDM改进的小波包图像传输方案,对比了平坦和非平坦多径衰落信道下WP-OFDM系统的误码性能.同时,提出了一种联合信源信道编码和自适应配置方案,得到了非均衡误差保护下的各种重要的SPHIT比特流.最后,仿真验证了文章所提出的图像传输方案的有效性.     

A progressive transmission image coder using linear phase uniformfilterbanks as block transforms

This paper presents a novel image coding scheme using M-channel linear phase perfect reconstruction filterbanks (LPPRFBs) in the embedded zerotree wavelet (EZW) framework introduced by Shapiro (1993). The innovation here is to replace the EZWs dyadic wavelet transform by M-channel uniform-band maximally decimated LPPRFBs, which offer finer frequency spectrum partitioning and higher energy compaction. The transform stage can now be implemented as a block transform which supports parallel processing and facilitates region-of-interest coding/decoding. For hardware implementation, the transform boasts efficient lattice structures, which employ a minimal number of delay elements and are robust under the quantization of lattice coefficients. The resulting compression algorithm also retains all the attractive properties of the EZW coder and its variations such as progressive image transmission, embedded quantization, exact bit rate control, and idempotency. Despite its simplicity, our new coder outperforms some of the best image coders published previously in the literature, for almost all test images (especially natural, hard-to-code ones) at almost all bit rates.     

基于人工视觉对比度掩模的鲁棒图像融合系统

现有的图像融合算法,不能有效区分噪声和视觉上有意义的特征,往往在输入含有噪声时性能变差。人类视觉系统对图像特征提取有特殊的机制。本文利用人类视觉系统对比度掩模过程对噪声和边缘信息的识别机制,在视觉域进行图像融合,达到自适应抑制噪声,增强图像特征的目的。对各方案性能的主、客观比较,充分验证了本文方案的优越性。     

A fast progressive image transmission scheme using block truncation coding by pattern fitting

In this paper, we have proposed a novel progressive image transmission scheme. In the present method, the concept of the BTC-PF is used for faster decoding. Here, images are decomposed into a number of blocks based on smoothness criterion. The smooth blocks are encoded by block means and the others are by BTC-PF method. To encode a block by BTC-PF method, the codebook is organized like a full search progressive transmission tree which helps greatly in efficient progressive transmission. The present method provides good image quality at low bit-rate and faster decoding compared to other spatial domain progressive transmission methods. We extend this method for color images also. In color image coding, each color plane is encoded separately and then the encoded information of the planes are transmitted in interleaving manner to obtain color images right from the early stages.     

Determination of optimal distortion-based protection in progressive image transmission: a heuristic approach

In this paper, we describe a method for fast determination of distortion-based optimal unequal error protection (UEP) of bitstreams generated by embedded image coders and transmitted over memoryless noisy channels. The UEP problem is reduced to the more general problem of finding a path in a graph, where each path of the graph represents a possible protection policy, with the objective of selecting the best path being that one inducing minimal distortion. The problem is combinatorially complex and excludes a brute force approach. The solution is provided by applying heuristic information from the problem domain to reduce search complexity. In particular, we use graph search procedure A suggested by Hart , well known in the field of artificial intelligence, to avoid exhaustive search. Numerical results show that this technique outperforms the method presented by Hamzaoui , in terms of Mean Square Error (MSE) distortion and computational complexity. After testing our solution using analytical models of the operational distortion curves proposed by Charfi , we implement a transmission architecture that, using the actual distortion values generated by a real embedded coder, computes the optimal protection policy for the considered image, protects the packets, and transmits them over a channel.     

Human visual weighted quantization for transform/subband imagecoding revisited for interlaced pictures

This article addresses the problem of human visual weighted quantization for transform/subband coding of interlaced pictures. Merged field coding is assumed. The criterion proposed for the optimization of the quantizer is the distortion measured on the deinterlaced and decoded image. This criterion and the associated weighting factors are shown to be dependent on the motion between two successive fields.