This paper presents an efficient quadtree based fractal image coding scheme in wavelet transform domain based on the wavelet based theory of fractalimage compression introduced by Davis. In the scheme, zerotrees of...
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This paper presents an efficient quadtree based fractal image coding scheme in wavelet transform domain based on the wavelet based theory of fractalimage compression introduced by Davis. In the scheme, zerotrees of wavelet coefficients are used to reduce the number of domain blocks, which leads to lower bit cost required to represent the location information of fractalcoding, and overall entropy constrained optimization is performed for the decision trees as well as for the sets of scalar quantizers and self quantizers of wavelet subtrees. Experiment results show that at the low bit rates, the proposed scheme gives about 1 dB improvement in PSNR over the reported results.
Traditionally, fractalimage compression suffers from lengthy encoding time in measure ofhours. In this paper, combined with characteristlcs of human visual system, a flexible classification technique is proposed. Thi...
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Traditionally, fractalimage compression suffers from lengthy encoding time in measure ofhours. In this paper, combined with characteristlcs of human visual system, a flexible classification technique is proposed. This yields a corresponding adaptive algorithm which can cut down the encoding timeinto second's magnitude. Experiment results suggest that the algorithm can balance the overall encodingperformance efficiently, that is, with a higher speed and a better PSNR gain.
fractal image coding based on Iterated Function System (IFS) has been attracting much interest because of the possibilities of drastic data compression It performs compression by using the self-similarity included in ...
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ISBN:
(纸本)0819427497
fractal image coding based on Iterated Function System (IFS) has been attracting much interest because of the possibilities of drastic data compression It performs compression by using the self-similarity included in an image. III the conventional schemes, under the assumption of the self-similarity in the image, each block (range block) is mapped from that larger block (domain block) which is considered as the most suitable block to approximate the range block. However, even if the exact self-similarity of an image is found at the encoder, it hardly holds at the decoder because a, domain pool of the encoder is different from that of the decoder. In this paper, we propose a fractal image coding scheme by using domain pools replaced with decoded or transformed values to reduce the difference between the domain pools af the encoder and that of the decoder. The proposed scheme performs two-state encoding. The domain pool is replaced with decoded non-contractive blocks first and then with transformed values far contractive blocks. It is expected that the proposed scheme reduces errors of contractive blocks in the reconstructed image while those of non-contractive blocks are kept unchanged. The experimental results show the effectiveness of the proposed scheme.
This paper proposes an analysis method of scaling-factor-quantization error in fractal image coding using a state-space approach with the statistical analysis method. It is shown that the statistical analysis method i...
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This paper proposes an analysis method of scaling-factor-quantization error in fractal image coding using a state-space approach with the statistical analysis method. It is shown that the statistical analysis method is appropriate and leads to a simple result, whereas the deterministic analysis method is not appropriate and leads to a complex result for the analysis of fractal image coding. We derive the output error variance matrix for the measure of error and define the output error variance by scalar quantity as the mean of diagonal elements of the output error variance matrix. Examples are given to show that the scaling-factor-quantization error due to iterative computation with finite-wordlength scaling factors degrades the quality of decoded images. A quantitative comparison uf experimental scaling-factor-quantization error with analytical result is made for the output error variance. The result shows that our analysis method is valid for the fractal image coding.
Roundoff error due to iterative computation with finite wordlength degrades the quality of decoded images in fractal image coding that employs a deterministic iterated function system. This paper presents a state-spac...
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Roundoff error due to iterative computation with finite wordlength degrades the quality of decoded images in fractal image coding that employs a deterministic iterated function system. This paper presents a state-space approach to round-off error analysis of fractal image coding for grey-scale images. The output noise variance matrix and the noise matrix are derived for the measures of error and the output noise variance is newly defined as the pixel mean of diagonal elements of the output noise matrix. A quantitative comparison of experimental roundoff error with analytical result is made for the output noise variance. The result shows that our analysis method is valid for the fractal image coding. Our analysis method is useful to design a real-time and low-cost decoding hardware with finite wordlength for fractal image coding.
We present an object-based fractalcoding scheme based on the partitioned iterative function system (PIFS) that is similar to the standard fractal image coding schemes. The partitioned blocks in our object-based fract...
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We present an object-based fractalcoding scheme based on the partitioned iterative function system (PIFS) that is similar to the standard fractal image coding schemes. The partitioned blocks in our object-based fractalcoding scheme are classified as boundary blocks and internal blocks according to their shapes. The boundary blocks are located in the boundary region of an object and their shapes are arbitrary, whereas the internal blocks are located in the internal region of an object and their shapes are square. As the internal blocks do not affect the blocks to appear in the process of the ordinary fractalcoding except that the domain pool is not an image but an object, encoding for the internal blocks follows the ordinary fractalcoding schemes as they are. However, the boundary blocks should be carefully handled, as they have properties that make them different from the internal blocks, i.e., they have arbitrary shapes and their domain pool is composed of the internal blocks not the boundary blocks. Considering these properties, we propose three methods to encode the boundary blocks by making an alteration to the shapes of range blocks and domain blocks, and a method to encode them using the predecoded internal blocks. The methods are mathematically analyzed and their performance is experimentally evaluated. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)01412-9].
A new fast fractal encoding algorithm based on the variances of image blocks is proposed. With the domain blocks sorted according to their variances, and the best matched domain block to a given range block is searche...
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A new fast fractal encoding algorithm based on the variances of image blocks is proposed. With the domain blocks sorted according to their variances, and the best matched domain block to a given range block is searched in the order that the variance-distance is closer. A great number of domain blocks could be safely rejected by the prior comparison of the current minimum distortion and variance difference between the candidate domain block and the range block during the search process. It was proved that our algorithm produces completely identical fractal codes with that of the conventional full search in reduced time. The simulation results confirmed the effectiveness of the proposed algorithm.
In this paper, we propose and evaluate a method for fractal image coding in the subband domain. The subband decomposition scheme acts as a classifier, which can efficiently reduce encoding time. The proposed fractal i...
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In this paper, we propose and evaluate a method for fractal image coding in the subband domain. The subband decomposition scheme acts as a classifier, which can efficiently reduce encoding time. The proposed fractal image coding scheme is an adaptive one. The adapt ability is based on the variance of each subband. At each subband, the scheme adaptively sets the map block size that should be encoded. In addition, the domain blocks are adaptively restricted to the neighborhood of their respective range block. Simulation results show that good picture quality of the coded image is obtained at 0.370 bpp. It also indicates that such an adaptive scheme makes a better trade-off between the required bit rate and picture quality than a fixed size one. Moreover, the adaptive scheme can save a large amount of time.
The fractal image coding technique has attracted a degree of interest for its low bit rate. But the reconstructed image is of medium quality. This problem has prevented the fractal technique from being practically use...
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The fractal image coding technique has attracted a degree of interest for its low bit rate. But the reconstructed image is of medium quality. This problem has prevented the fractal technique from being practically used. In order to improve the compression fidelity, a new affine transformation is proposed in this paper. Meanwhile, its contractivity requirement is analyzed, and the optimal parameters are derived using the least square method. The new affine transformation has been practically used in imagecoding. Experiments show that the PSNR can reach 28.7dB at a compression ratio (CR) of 16.4 for the 256 x 256 x 8 "Lena" image. Comparison with other fractalcoding schemes shows that the new affine transformation can improve the reconstructed image quality efficiently.
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