AN IMPROVED FRACTAL IMAGE CODING METHOD

This paper presents a fast fractal image coding method based on quadtree division, improved neighbor search and asymptotic strategy. We search the optimal matched domain block of a range block in its five nearest neighbor blocks and make asymptotic moves along the direction of potential optimal solution. If the optimal solution can not be improved, we carry out quadtree division for this range block until it caters to our demand or reaches greatest division level. The experimental results show that the coding speed of the proposed method declined slightly, but it has a better quality of reconstructed image and higher compression ratio in comparisons with no search method.

Download Full-text

Modified No Search Scheme based Domain Blocks Sorting Strategies for Fractal Image Coding

Zeitschrift für Naturforschung A ◽

10.5560/zna.2014-0042 ◽

2014 ◽

Vol 69 (10-11) ◽

pp. 511-520

Author(s):

Xing-Yuan Wang ◽

Dou-Dou Zhang ◽

Na Wei

Keyword(s):

Mean Square Error ◽

Image Coding ◽

The Other ◽

Mean Square ◽

Minimum Value ◽

Fractal Image ◽

Fractal Image Coding ◽

Domain Block ◽

Partition Method

AbstractA novel fractal image coding algorithm based on domain blocks sorting strategies and modified no search scheme is proposed in this paper. On one hand, in order to improve the encoding time, a modified no search (MNS) scheme is adopted. Firstly, the image is divided into blocks of different size utilizing an adaptive quadtree partition method. Secondly, one finds the location of the best matching domain block using the MNS scheme for the range blocks, whose sizes are larger than the preset minimum value. Thirdly, the types of the range block and domain block are computed employing the proposed approach, and then the corresponding computation of mean square error (MSE) is determined. The computation of the MSE is reduced and the encoding phase speeds up. On the other hand, the range blocks with the minimal sizes are encoded applying the proposed domain blocks sorting (DBS) method. Contrast experiment results show that the proposed algorithm can obtain good quality of the reconstructed images and shorten the encoding time significantly.

Download Full-text

Improvement of Fractal Image Compression Coding Based on Quadtree

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.532-533.1157 ◽

2012 ◽

Vol 532-533 ◽

pp. 1157-1161

Author(s):

Hong Tao Hu ◽

Qi Fei Liu

Keyword(s):

Image Compression ◽

Image Coding ◽

Original Image ◽

Fractal Image Compression ◽

Fractal Image ◽

Fractal Image Coding ◽

Global Matching ◽

Domain Block ◽

Compression Coding

The goal of image compression is to represent an image with as few number of bits as possible while keeping the quality of the original image. With the characteristics of higher compression ratio, fractal image coding has received much attention recently. However, conventional fractal compression approach needs more time to code the original image. In order to overcome the time-consuming issue, a Quadtree-based partitioning and matching scheme is proposed. During the partitioning phase, an image frame is partitioned into tree-structural segments. And during a matching phase, a rang block only searches its corresponding domain block around previous matched domain block. Such local matching procedures will not stop until a predefined matching threshold is obtained. The preliminary experimental results show that such sub-matching rather than a global matching scheme dramatically decreases the matching complexity, while preserving the quality of an approximate image to the original after decoding process. In particular, the proposed scheme improves the coding process up to 2 times against the conventional fractal image coding approach.

Download Full-text

Fast Fractal Image Coding Method Based on RMSE and DCT Classification

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.241-244.3034 ◽

2012 ◽

Vol 241-244 ◽

pp. 3034-3039

Author(s):

Xian Qiang Lv ◽

Song Yang ◽

Xin Zhang ◽

Ying Wang ◽

Yun Feng Shi ◽

...

Keyword(s):

Image Coding ◽

Nearest Neighbor ◽

Search Space ◽

Image Block ◽

Fractal Image ◽

Coding Method ◽

Long Time ◽

Dct Coefficients ◽

Fractal Encoding ◽

Domain Block

To solve the problem of long time consuming in the fractal encoding process, a fast fractal encoding algorithm based on RMSE (Root mean square error) and DCT (Discrete Cosine Transform) classification is proposed. During the encoding process, firstly, the image is divided into range blocks and domain blocks by quadtree partition according to RMSE, then, according to DCT coefficients of image block, three classes of image blocks are defined, which are smooth class, horizontal/vertical edge class, diagonal/sub-diagonal class. At last, every range block is limited to search the best matched block in the corresponding domain block class, and the fractal coding are recorded until the process is completed. When searching the best matched block, the nearest neighbor block will be found in the sense of RMSE in the ordered codebook, and the best matched block will be further found in the vicinity of the nearest neighbor block. The experimental results show that the proposed algorithm can efficiently reduce the search space and shorten the encoding time, while achieving the same reconstructed image quality as that of the full search method.

Download Full-text

An accelerated method to predict the quality of decoded images in fractal image coding

2015 8th International Congress on Image and Signal Processing (CISP) ◽

10.1109/cisp.2015.7407873 ◽

2015 ◽

Author(s):

Qiang Wang ◽

Sheng Bi ◽

Guohua Jin

Keyword(s):

Image Coding ◽

Fractal Image ◽

Fractal Image Coding

Download Full-text

CRYPTANALYSIS ON SECURE FRACTAL IMAGE CODING BASED ON FRACTAL PARAMETER ENCRYPTION

Fractals ◽

10.1142/s0218348x12500041 ◽

2012 ◽

Vol 20 (01) ◽

pp. 41-51 ◽

Cited By ~ 5

Author(s):

CHING-HUNG YUEN ◽

KWOK-WO WONG

Keyword(s):

Image Coding ◽

Standard Test ◽

Scaling Factor ◽

Depth Information ◽

Selective Encryption ◽

Fractal Parameter ◽

Fractal Image ◽

Fractal Image Coding ◽

Plain Image ◽

Domain Block

The vulnerabilities of the selective encryption scheme for fractal image coding proposed by Lian et al.1 are identified. By comparing multiple cipher-images of the same plain-image encrypted with different keys, the positions of unencrypted parameters in each encoded block are located. This allows the adversary to recover the encrypted depth of the quadtree by observing the length of each matched domain block. With this depth information and the unencrypted parameters, the adversary is able to reconstruct an intelligent image. Experimental results show that some standard test images can be successfully decoded and recognized by replacing the encrypted contrast scaling factor and brightness offset with specific values. Some remedial approaches are suggested to enhance the security of the scheme.

Download Full-text