Shape Adaptive Discrete Wavelet Research Articles

No reference image quality assessment with shape adaptive discrete wavelet features using neuro-wavelet model

No reference image quality assessment with shape adaptive discrete wavelet features using neuro-wavelet model

ROI-Based Compression Strategy of 3D MRI Brain Datasets for Wireless Communications

ObjectivesBecause of the large amount of medical imaging data, the transmission process becomes complicated in telemedicine applications. Thus, in order to adapt the data bit streams to the constraints related to the limitation of the bandwidths a reduction of the size of the data by compression of the images is essential. Despite the improvements in the field of compression, the transmission itself can also introduce errors. For this reason, it is important to develop an adequate strategy which will help reduce this volume of data without having to introduce some distortion and resist the errors introduced by the channel noise during transmission. Thus, in this paper, we propose a ROI-based coding strategy and unequal bit stream protection to meet this dual constraint. Material and methodsThe proposed ROI-based compression strategy with unequal bit stream protection is composed of three parts: the first one allows the extraction of the ROI region, the second one consists of a ROI-based coding and the third one allows an unequal protection of the ROI bit stream.First, the Regions Of Interest (ROI) are extracted by hierarchical segmentation of these regions according to a segmentation method based on the technique of Marker-based-watershed combined with the technique of active contours by level set. The resulting regions are selectively encoded by a 3D coder based on a shape adaptive discrete wavelet transform 3D-BISK, where the compression ratio of each region depends on its relevance in diagnosis. These obtained regions of interest are protected with an error-correcting code of Reed-Solomon type with a code rate that varies according to the relevance of the region by an unequal protection strategy (UEP). ResultsThe performance of the proposed compression scheme is evaluated in several ways. First, tests are performed to study the impact of errors on the different bit streams. In the first place, these tests are carried out in order to study the effect of the variation of the compression rates on the different bit streams. Secondly, different Reed Solomon error-correcting codes of different code rates are tested at different compression rates on a BSC channel. Finally, the performances of this coding strategy are compared with those of SPIHT 3D in the case of transmission on a BSC channel. ConclusionThe obtained results show that the proposed method is quite efficient in transmission time reduction. Therefore, our proposed scheme will reduce the volume of data without having to introduce some distortion and resist the errors introduced by the channel noise in the case of telemedicine.

A New Approach to Region Based Image Retrieval using Shape Adaptive Discrete Wavelet Transform

In this paper, we present an efficient region-based image retrieval method, which uses multi-features color, texture and edge descriptors. In contrast to recent image retrieval methods, which use discrete wavelet transform (DWT), we propose using shape adaptive discrete wavelet transform (SA-DWT). The advantage of this method is that the number of coefficients after transformation is identical to the number of pixels in the original region. Since image data is often stored in compressed formats: JPEG 2000, MPEG 4…; constructing image histograms directly in the compressed domain, allows accelerating the retrieval operation time, and reducing computing complexities. Moreover, SA-DWT represents the best way to exploit the coefficients characteristics, and properties such as the correlation. Characterizing image regions without any conversion or modification is first addressed. Using edge descriptor to complement image region characterizing is then introduced. Experimental results show that the proposed method outperforms content based image retrieval methods and recent region based image retrieval methods

SAR IMAGE DESPECKLING BASED ON ADAPTIVE WINDOW AND SHAPE ADAPTIVE-DISCRETE WAVELET TRANSFORM

By considering the prior knowledge of SAR image in spatial domain and the property of coefficients in wavelet domain,a novel algorithm of SAR image despeckling was presented.An adaptive window was constructed and a uniform region for every pixel of SAR image was found by using local polynomial approximation-intersection of confidence intervals(LPA-ICI).Hard-threshold shrinkage despeckling was implemented with fast shape adaptive discrete wavelet transform proposed in this paper.At last,many despeckled samples were fused into a final despeckled SAR image according to the sparsity of regions.Experiments show that the algorithm proposed here has advanced despecking performance.Especially,reconstructed image has no unpleasant ringing artifacts,and it efficiently reserves point targets of original SAR image.

Shape adaptive wavelet transform for magnetic resonance images coding

Region-based coding is an important feature in today's image coding techniques as it follows different regions of the image that will be encoded at different bit rates and hence at different qualities rather than encoding the entire image with a single quality constraints. This article proposes an algorithm for the region-based coding of the brain magnetic resonance images in which the brain part will be encoded with more number of bits than the background. This method employs Shape Adaptive Discrete Wavelet Transform, which can transform the regions of interest and the background on the images independently and the coefficients can be encoded by using the SPIHT coding at different levels. This algorithm was compared with the existing wavelet-based coding techniques and a better PSNR was achieved for the same bit rate by reconstructing the region of interest with high quality than the background.

Performance Evaluation of Magnetic Resonance Images Coding Using Shape Adaptive Discrete Wavelet Transform

Region based coding is an important feature in today's image coding techniques as it follows different regions of the image will be encoded at different bit rates and hence at different qualities rather than encoding the entire image with a single quality constraints. This paper evaluates the features of using Shape Adaptive Wavelet Transform for the region based coding of the brain magnetic resonance images, in which the brain part will be encoded with more importance than the background. Shape Adaptive Discrete Wavelet Transform (SA-DWT) can transform the regions of interest and the background on the images independently and the coefficients can be encoded by using the SPIHT coding at different levels. This algorithm was compared with the existing wavelet based coding techniques and a better PSNR was achieved for the same bit rate by reconstructin g the region of interest with high quality than the background. lossless schemes and also maintain the quality of the image. Volumetric medical data are image sequences of any organ for the three dimensional view. These images are correlated both within and across slices to eliminate the redundancy. Some of the existing 3D compression techniques used motion compensation and encoded the image by the mesh formation. The deformation across the slices of the sequence is modeled as motion and the motion compensation algorithm is used to exploit the correlation between the slices (1). This method can provide a lossless compression of the sequence but with increased expense of complexity. Region based compression methods based on wavelet transforms can perform better with relatively less complexity. In JPEG 2000 part - 1 (2), max-shift ROI coding is used which exploits intra band dependency and adopts EBCOT (3) algorithm for coding the bit planes of wavelet coefficients. In this, it is not necessary to send the shape information as side information for decoding but the coefficients will blend with the pixels at the boundary between the ROI and the background. In JPEG 2000 part- 2 (4), scaling based ROI coding is adopted whereby the coefficients associated with the ROI are scaled up by a certain number of bitshift and then the bit planes of the coefficients are encoded plane by plane.

Formal photograph compression algorithm based on object segmentation

Small storage space for photographs in formal documents is increasingly necessary in todays needs for huge amounts of data communication and storage. Traditional compression algorithms do not sufficiently utilize the distinctness of formal photographs. That is, the object is an image of the human head, and the background is in unicolor. Therefore, the compression is of low efficiency and the image after compression is still space-consuming. This paper presents an image compression algorithm based on object segmentation for practical high-efficiency applications. To achieve high coding efficiency, shape-adaptive discrete wavelet transforms are used to transformation arbitrarily shaped objects. The areas of the human head and its background are compressed separately to reduce the coding redundancy of the background. Two methods, lossless image contour coding based on differential chain, and modified set partitioning in hierarchical trees (SPIHT) algorithm of arbitrary shape, are discussed in detail. The results of experiments show that when bit per pixel (bpp)is equal to 0.078, peak signal-to-noise ratio (PSNR) of reconstructed photograph will exceed the standard of SPIHT by nearly 4dB.

Optimal Bit Allocation for Joint Texture-Aware Contour-Based Shape Coding and Shape-Adaptive Texture Coding

In this paper, an operationally optimal joint shape and texture coding algorithm is proposed that uses shape-adaptive texture coding as well as texture-aware shape coding. The solution is optimal in the operational rate distortion sense, i.e, given the coding setup, the solution will guarantee the smallest possible distortion for a given rate. The shape is approximated using polygons or higher order curves. We also consider biasing the cost function to favor horizontal and vertical edges for the case of polygon approximation (biased polygon approximation). The texture is encoded using shape-adaptive discrete cosine transform or shape-adaptive discrete wavelet transform of the MPEG-4 video codec. A comparison is drawn between the two techniques. Both a fixed-width and a variable-width tolerance band for shape coding are considered. The variable width of the tolerance band is a function of the texture profile, i.e, the width is inversely proportional to the magnitude of the image gradient. Experimental results are presented and conclusions are drawn.

3-D Object-Based Scalable Wavelet Video Coding With Boundary Effect Suppression

This paper extends the lifting-based motion threading (MTh) technique from the frame-based coding to the object-based coding, attracted by the unique advantages of the object-based coding that do not exist in other coding schemes. The boundary effects, which exist in spatial and temporal wavelet transforms due to the manner of object-based coding, are well suppressed by 3-D shape-adaptive discrete wavelet transform (3D SA-DWT) via the lifting implementation in a unified framework. Based on the proposed object-based MTh technique, a 3-D object-based scalable wavelet video coder is developed. Experimental results show that the proposed coder achieves good performance compared with the existing object-based coders and provides the scalability functionality at the same time

SPIHT-Based Coding of the Shape and Texture of Arbitrarily Shaped Visual Objects

A new scheme for coding both the shape and texture of arbitrarily shaped visual objects is presented. Based on set partitioning on hierarchical trees (SPIHT), the proposed Shape and Texture SPIHT (ST-SPIHT) employs a novel implementation of the shape-adaptive discrete wavelet transform (SA-DWT) using in-place lifting, along with parallel coding of texture coefficients and shape mask pixels to create a single embedded code that allows for fine-grained rate-distortion scalability. The single output code simplifies the logistics of object storage and transmission compared to previously published schemes. An input parameter provides control over the relative progression between shape and texture coding in the embedded code, allowing for adjustment of the emphasis of shape versus texture quality in low bit rate reconstructions. The combination of features provided by ST-SPIHT, namely, explicit and progressive shape coding in parallel with wavelet-based embedded coding of the object texture, is unique compared to previously published schemes. Computational complexity is minimized since the shape coding takes advantage of the decomposition and spatial orientation trees used for texture coding. Objective and subjective simulation results show that the proposed ST-SPIHT scheme has rate-distortion performance comparable or superior to MPEG-4 Visual Texture Coding for most bit rates

Embedded wavelet packet object-based image coding based on context classification and quadtree ordering

In this paper, an object-based embedded image coding algorithm based on context classification and quadtree ordering in wavelet packet domain (OB-CCAQO) is proposed. To match up well with the quadtree-based embedded coder, a new cost function for the best basis selection is adopted in SA-DWPT (shape adaptive discrete wavelet packet transform). The significance probability of wavelet coefficient is estimated by convoluting a 9 × 9 FIR filter matrix kernel with the significance states of neighboring coefficients, and then a context classifier based on Lloyd–Max algorithm is used to categorize the wavelet coefficients with the same or similar significance probability into several contexts. The significance state of wavelet coefficient with respect to a given threshold is encoded using adaptive arithmetic coder based on the classified context. In addition, combined with the structure of the best wavelet packet basis, a complete quadtree representation of wavelet packet coefficients is established to explore the ordering procedure of embedded object-based image coding. Experimental results show that the proposed object-based embedded image coder offers coding performance superior to the popular object-based coders and is also comparable to or better than the state-of-art embedded image coder when applied in the framed-based image coding.

VLSI Architecture for Lifting-Based Shape-Adaptive Discrete Wavelet Transform with Odd-Symmetric Filters

In this paper, a VLSI architecture for lifting-based shape-adaptive discrete wavelet transform (SA-DWT) with odd-symmetric filters is proposed. The proposed architecture is comprised of a stage-based boundary extension strategy and the shape-adaptive boundary handling units. The former could reduce the complexity of multiplexers that are introduced to solve the shape-adaptive boundary extension. The latter consists of two multiplexers and can solve the shape-adaptive boundary extension locally without any additional register. Two case studies are presented, including the JPEG 2000 default (9, 7) filter and MPEG-4 default (9, 3) filter. According to comparison results with previous architectures, the efficiency of the proposed architectures is proven.

A low memory zerotree coding for arbitrarily shaped objects

The set partitioning in hierarchical trees (SPIHT) algorithm is a computationally simple and efficient zerotree coding technique for image compression. However, the high working memory requirement is its main drawback for hardware realization. We present a low memory zerotree coder (LMZC), which requires much less working memory than SPIHT. The LMZC coding algorithm abandons the use of lists, defines a different tree structure, and merges the sorting pass and the refinement pass together. The main techniques of LMZC are the recursive programming and a top-bit scheme (TBS). In TBS, the top bits of transformed coefficients are used to store the coding status of coefficients instead of the lists used in SPIHT. In order to achieve high coding efficiency, shape-adaptive discrete wavelet transforms are used to transformation arbitrarily shaped objects. A compact emplacement of the transformed coefficients is also proposed to further reduce working memory. The LMZC carefully treats "don't care" nodes in the wavelet tree and does not use bits to code such nodes. Comparison of LMZC with SPIHT shows that for coding a 768 /spl times/ 512 color image, LMZC saves at least 5.3 MBytes of memory but only increases a little execution time and reduces minor peak signal-to noise ratio (PSNR) values, thereby making it highly promising for some memory limited applications.

Shape-adaptive discrete wavelet transforms for arbitrarily shaped visual object coding

This paper presents a shape-adaptive wavelet coding technique for coding arbitrarily shaped still texture. This technique includes shape-adaptive discrete wavelet transforms (SA-DWTs) and extensions of zerotree entropy (ZTE) coding and embedded zerotree wavelet (EZW) coding. Shape-adaptive wavelet coding is needed for efficiently coding arbitrarily shaped visual objects, which is essential for object-oriented multimedia applications. The challenge is to achieve high coding efficiency while satisfying the functionality of representing arbitrarily shaped visual texture. One of the features of the SA-DWTs is that the number of coefficients after SA-DWTs is identical to the number of pixels in the original arbitrarily shaped visual object. Another feature of the SA-DWT is that the spatial correlation, locality properties of wavelet transforms, and self-similarity across subbands are well preserved in the SA-DWT. Also, for a rectangular region, the SA-DWT becomes identical to the conventional wavelet transforms. For the same reason, the extentions of ZTE and EZW to coding arbitrarily shaped visual objects carefully treat "don't care" nodes in the wavelet trees. Comparison of shape-adaptive wavelet coding with other coding schemes for arbitrarily shaped visual objects shows that shape-adaptive wavelet coding always achieves better coding efficiency than other schemes. One implementation of the shape-adaptive wavelet coding technique has been included in the new multimedia coding standard MPEG-4 for coding arbitrarily shaped still texture. Software implementation is also available.

Arbitrarily shaped image coding by using translation invariant wavelet transforms

This study presents two sets of translation invariant wavelet transforms for coding an arbitrarily shaped image. Each set can be viewed as a shape-adaptive discrete wavelet transform (SA-DWT) with the property of translation invariance. The proposed transform schemes have the following merits: (1) they are translation invariant, (2) no sharp transition appears at the edges of the image, (3) the number of pixels is maintained constant after transformation, (4) the correlation of pixels is fully exploited, and (5) the property of self-similarity across scales is preserved.