Megumi Takezawa

A genetic-algorithm based quantization method for fractal image coding

This paper proposes a high-accuracy quantization method for IFS parameters in fractal image coding by using a genetic algorithm (GA). The development of IFS-parameter quantization techniques is significant for the image coding because its errors make more serious problems in the iteration procedures than the other quantization topics. Even if the errors are small, high-quality reconstructed images are not necessarily obtained. Therefore, the high-accuracy quantization methods are required for the parameters. The proposed method provides higher quality reconstructed images than a conventional method which merely minimizes the errors.

An image restoration method using IFS

This paper proposes a new image restoration method based on the iterated function system (IFS). The proposed method can restore images contaminated by impulsive noise according to self-similarity represented by the IFS parameters. Since the IFS is usually used for image coding, it has never been applied to image restoration; and it cannot be utilized for image restoration as it is. In order to adapt the IFS for image restoration, this paper reforms the conventional criterion for the computation of the IFS parameters to suit for image restoration, and as preprocessing we apply an /spl epsiv/-filter in which a median filter is embedded to contaminated images prior to computing the IFS parameters. Some simulation results are presented to demonstrate the effectiveness of this method.

Quality improvement technique for JPEG images with fractal image coding

This paper proposes a quality improvement technique for JPEG images by using fractal image coding. JPEG coding is a commonly used standard method of compressing images. However, in its decoded images, quantization noise is sometimes visible in high frequency regions, such as the edges of objects. Hence, in order for the JPEG coding to become a more powerful image-coding method, the JPEG image quality must be improved. Therefore, our method solves this problem by adding the obtained codes by the fractal image coding to improve the image quality. Some simulation results verify that the proposed method achieved higher coding-performance than the traditional JPEG coding.

Transmission-line filter synthesis using genetic algorithms

Summary form only given. We present a new method for designing transmission-line filters with shunt-connected open circuit stubs. This method is based on a genetic algorithm and can effectively be applied to various filter design problems without increasing the computational complexity. Conventional methods of designing and implementing transmission-line filters begin with lumped-element prototype filters. As a result, transmission-line filters must be created using transmission-line sections of the same electrical length. If this limitation could be avoided, however, it might be possible to design transmission-line filters with better characteristics than those of conventional filters. To evaluate the proposed method, several different types of filters were synthesized according to the proposed method.

Quality Improvement of JPEG Images Based on Fractal Image Coding

We proposed high accuracy JPEG coding by including fractal image coding. JPEG coding is a commonly used standard method of accurately compressing images. However, in its decoded images, quantization errors occur especially in the region of high frequencies, such as object edges. Our method solved this problem by adding the obtained codes by fractal image coding to improve image quality in high frequency regions. Thus, our method achieved higher coding-performance than the traditional JPEG coding.

A GA and SA-Based Fractal Image Coding

This paper proposes a fast search technique using a genetic algorithm (GA) including a simulated annealing (SA) algorithm for the optimal parameters of the iterated function system (IFS) utilized in fractal image coding. The heavy computational costs of the previous methods to find the optimal IFS parameters are a serious problem, and in order to overcome it, we have already proposed a GA-based technique to find them in short time. However, its reduction is not enough for the practical use. Therefore, the proposed method achieves further reduction by including an SA search in the GA search. Some simulation results show that the proposed method achieves more reduction in the computational costs than the only GA-based method does.

Ultra low bit-rate image coding algorithm based on fractal image coding

This paper proposes a low bit-rate fractal image coding algorithm for wireless communication. The fractal image coding is well known for its high compression performance. This performance is useful for future wireless communications with narrow-band. However, in order to become a powerful image coding technique for wireless communications, its reconstructed image quality must be improved. Therefore, to achieve further quality improvement, a novel fractal image coding algorithm is proposed. Some simulation results verify that the proposed method can reconstruct images with 1.4 dB higher quality than JPEG at low bit-rates below 0.12 bits pixel and also higher quality than JPEG2000 at very low bit-rates below 0.035-0.05 bits pixel.

An IFS-based image restoration method for impulsive noise contamination

This paper proposes an Iterated Function System (IFS) based image-restoration method. The proposed method can restore images corrupted by impulsive noise according to self-similarity represented by the IFS. Since the IFS is usually used for image coding, it has never been applied to image restoration; and it cannot be utilized for the image restoration as it is. In order to adapt the IFS for image restoration, this paper reforms the conventional criterion for the computation of the IFS parameters to suit for image restoration, and as preprocessing we apply a median filter to the contaminated images prior to computing the IFS parameters. Some simulation results are presented to demonstrate the effectiveness of this method.