A fractal image coding scheme using classified range regions is proposed. Two classes of range regions. shade and nonshade, are defined here, A shade range region is encoded by the average gray level, while a nonshade...
详细信息
A fractal image coding scheme using classified range regions is proposed. Two classes of range regions. shade and nonshade, are defined here, A shade range region is encoded by the average gray level, while a nonshade range region is encoded by IFS parameters. To obtain classified range regions, the two-stage block merging scheme is proposed. Each range region is produced by merging primitive square blocks. Shade range regions are obtained at the first stage, and from the rest of primitive blocks nonshade range regions are obtained at the second stage. Furthermore, for increasing the variety of region shape, the 8-directional block merging scheme is defined by extension of the 4-directional scheme. Also, two similar schemes for encoding region shapes, each corresponding to the 4-directional block merging scheme and the 8-directional block merging scheme, are proposed. From the results of simulation by using a test image, it was demonstrated that the variety of region shape allows large shade range regions to be extracted efficiently, and these large shade range regions are more effective in reduction of total amount of codebits with less increase of degradation of reconstructed image quality than large nonshade range regions. The 8-directional merging and coding scheme and the 4-directional scheme reveal almost the same coding performance, which is improved than that of the quad-tree partitioning scheme. Also, these two schemes achieve almost the same reconstructed image quality.
In this paper, a fractalimage compression system based on adaptive variable shape block transform is proposed. The procedure can be divided into approximately two basic phases: the classification phase and the adapti...
详细信息
In this paper, a fractalimage compression system based on adaptive variable shape block transform is proposed. The procedure can be divided into approximately two basic phases: the classification phase and the adaptive shape block phase. In the classification phase, a testing image block is assigned to its own class according to its direction attribute. The direction of the block is estimated by employing the technique of projection/backprojection which is a tomographic image reconstruction skill. Due to computational complexity, only four projection directions are resolved to construct the projection classification algorithm (PCA). Computer simulations show that the proposed classification method outperforms the gradient classification algorithm. In the adaptive shape block phase, PCA and the algorithm of split/merge are incorporated to form the variable shape block transformation. For the range blocks and domain blocks, we define fifteen merging patterns and ten shape components in the searching algorithm. Under this fractalcoding approach, a better trade-off between the decoded image quality and transmitting bit rate is performed. Several examples are presented to show the effectiveness of this coding system.
In traditional fractal image coding schemes, domain blocks are constrained to be twice as large as range blocks in order to ensure the convergence of the iterative decoding stage. However, this constraint has limited ...
详细信息
ISBN:
(纸本)0819442798
In traditional fractal image coding schemes, domain blocks are constrained to be twice as large as range blocks in order to ensure the convergence of the iterative decoding stage. However, this constraint has limited the fractal encoder to exploit the self-similarity of the original image. In order to overcome the shortcoming, a novel scheme using same sized range and domain blocks is proposed in the letter. Experimental results show the remarkable improvement in compression ratio and image quality.
Since Jacquin proposed original fractalimage compression technique in 1990, fractalcoding method has been developed into various schemes. Traditionally, fractalcoding uses mean square error (MSE) to evaluate simila...
详细信息
ISBN:
(纸本)9781457713033
Since Jacquin proposed original fractalimage compression technique in 1990, fractalcoding method has been developed into various schemes. Traditionally, fractalcoding uses mean square error (MSE) to evaluate similarity of image blocks, but the similarity evaluated by MSE usually differs from human visual system (HVS). Compared with MSE, structural similarity (SSIM) is an image measure index which is more appropriate for the HVS. This paper proposes a new fractalcoding scheme which uses structural similarity to measure the similarity between image blocks and compute these blocks' coefficients. The experiment results show that the proposed method generates higher quality images for the HVS than MSE scheme.
A chaos-based cryptosystem for fractal image coding is proposed. The Renyi chaotic map is employed to determine the order of processing the range blocks and to generate the keystream for masking the encoded sequence. ...
详细信息
A chaos-based cryptosystem for fractal image coding is proposed. The Renyi chaotic map is employed to determine the order of processing the range blocks and to generate the keystream for masking the encoded sequence. Compared with the standard approach of fraetal imagecoding followed by the Advanced Encryption Standard, our scheme offers a higher sensitivity to both plaintext and ciphertext at a comparable operating efficiency. The keystream generated by the Renyi chaotic map passes the randomness tests set by the United States National Institute of Standards and Technology, and so the proposed scheme is sensitive to the key.
作者：
Chen, XZhu, GXZhu, YTHuazhong Univ Sci & Technol
Inst Pattern Recognit & Artificial Intelligence Elect & Informat Engn Dept State Educ Commiss Lab Image Proc & Intelligent C Wuhan 430074 Peoples R China
Though it promised a high compression ratio and high decompression quality, the low fractal image coding speed blocked its way to practical application. The main problem of the low coding speed is due to the long sear...
详细信息
ISBN:
(纸本)0819430064
Though it promised a high compression ratio and high decompression quality, the low fractal image coding speed blocked its way to practical application. The main problem of the low coding speed is due to the long searching time of matching between domain blocks and range blocks. Genetic algorithms (GAs) are well known as a search and optimization technique based loosely on the principles of natural selection. In order to decrease the coding time, here a method is proposed that employs Genetic algorithms to solve the matching problem of fractal image coding. Experimental results indicate that the introduction of GAs to fractal image coding is a good way to increase the speed of fractal image coding without decreaseing the image quality obviously.
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 ...
详细信息
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.
image annotation is a process of assigning metadata to digital images in the form of captions or keywords, and has been regarded as image management and one of the most crucial processes of image retrieval. And many a...
详细信息
image annotation is a process of assigning metadata to digital images in the form of captions or keywords, and has been regarded as image management and one of the most crucial processes of image retrieval. And many automatic methods have been proposed. However, these methods still have some problems respectively. fractals are fragmented geometries and can be considered separate parts;each part is similar to the contracted overall shape. fractal features provide geometric information of an image that is irrelevant to the shape and size of an object in the image;therefore, fractal features are more robust than color and texture features. Therefore, this study proposed a fractal-driven image annotation (FIA) schema that extracts fractal features through fractal image coding and integrates color and texture as new visual features to conduct image-based annotation. Experimental results indicate that the effect of thresholds on annotating accuracy is insignificant. This finding supports the application of FIA on complex practical environments, reduces the time for identifying the optimal thresholds, and improves the practicality of using FIA in real environments. (c) 2012 Elsevier Ltd. All rights reserved.
In this paper a fast and efficient no-search fractal image coding method based on a modified gray-level transform which uses a fitting plane is presented. The improved gray-level transform can reduce the minimum match...
详细信息
In this paper a fast and efficient no-search fractal image coding method based on a modified gray-level transform which uses a fitting plane is presented. The improved gray-level transform can reduce the minimum matching error between a given range block and its corresponding domain block, and thus, it can enhance the possibility of successful domain-range matching. In comparison with our previous scheme which uses an adaptive plane, the improved scheme results in a considerable acceleration of the encoding process, decreases the compression ratio and improves the quality of the reconstructed images in the meanwhile. Comparing with Furao's no-search scheme, our improved scheme can get higher PSNR at higher bpp and almost the same PSNR at lower bpp. Although it uses more transform coefficients, such a fitting plane method can speed up the encoding process with the quality of the reconstructed images improved. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
This paper proposes an analysis method of the roundoff error due to finite-wordlength decoding in fractal image coding. The proposed method can be applied to large images such as 256 x 256 or 512 x 512 images because ...
详细信息
This paper proposes an analysis method of the roundoff error due to finite-wordlength decoding in fractal image coding. The proposed method can be applied to large images such as 256 x 256 or 512 x 512 images because it needs no complex matrix computation. The simplified model used here ignores the effect of decimation ratio on the roundoff error because it is negligible. As an analysis result, the proposed method gives the output error variance which consists of grey-tone scaling coefficients and an iteration number. This method is tested on various types of 12 standard images which have 256 x 256 size or 512 x 512 size with 256 grey levels. Comparisons of simulation results with analysis results are given. The results show that our analysis method is valid for the fractal image coding.
暂无评论