It is very important to control the bit-rate for video communication under a limited capacity of communication channel like wireless communication system because of large amout of data. In this paper, we propose a new adaptive pre-filter to improve the bit-rate in video compression, which preserves visually significant portion of the original image and smooth only insignificant portion actively. We focus on the differential signals between the original image and its filtered one and control the degree of smoothing by considering the power of local differential signals to produce various kinds of intermediate images betwwen both images. We conducted some computer simulations to check the performance of our scheme for the standard MPEG-4 video compression algorithm. Consequently, we could achieve further improvement of compression ratio while improving visual image quality than a conventional scheme.
In this work, we propose a new digital watermarking scheme for extremely high-resolution printing images applicable to On-Demand Publishing (ODP) system. We designed our scheme by considering the following requirements: (i) high image quality, (ii) high security, and (iii) watermark immunity (robustness). In order to attain these requirements we employ the idea of Spread Spectrum (SS) watermarking technique in our scheme and modify it to be applicable to color (CMYK) binary printing images. Simulation results verified that we could embed a watermark spreading over the entire output image as a weak energy and still keep high image quality. Also the watermark could be robustly decoded by controlling some parameters even after some possible attacks by a third party.
In this work, we extend arithmetic coding and present a data encryption scheme that achieves data compression and data security at the same time. This scheme is based on a chaotic dynamics, which makes use of the fact that the decoding process of arithmetic coding scheme can be considered as the repetition of Bernoulli shift map. Data encryption is achieved by controlling the piecewise linear maps by a secret key in three kinds of approach: (i) perturbation method, (ii) switching method, and (iii) source extension method. Experimental results show that the obtained arithmetic codes for a message are randomly distributed on the mapping domain [0,1) by using different keys without seriously deteriorating the compression ratio, and the transition of the orbits in the domain [0,1) is similar to the chaotic dynamics.
In this work we focus on the indexed triangle strips that is an extended representation of triangle strips to improve the efficiency for geometrical transformation of vertices, and present a method to construct optimum indexed triangle strips using Genetic Algorithm (GA) for real-time visualization. The main objective of this work is how to optimally construct indexed triangle strips by improving the ratio that reuses the data stored in the cash memory and simultaneously reducing the total index numbers with GA. Simulation results verify that the average index numbers and cache miss ratio per polygon cold be small, and consequently the total visualization time required for the optimum solution obtained by this scheme could be remarkably reduced.
This paper presents a new truncated Baker transformation with a finite precision and extends it to an efficient image encryption scheme. The truncated Baker transformation uses the quantization error as a secret key, which is always produced by contraction mechanism in the mapping process. The original dynamics by Baker transformation is globally preserved but a random level rotation operator is incorporated between two neighbor elements in the mapping domain in order to keep the same precision. Such perturbations are local and small in each mapping, however, as the mapping process goes on they will gradually accumulate and affect the whole dynamics. Consequently, generated binary sequences (the dynamics of elements) have statistically good features on ergodicity, mixing and chaotic properties. The extended image encryption scheme efficiently shuffle the input gray level image making difficult for a third party to decode the ciphered data to the original image without knowing the proper secret key.
Due to the drastic development of Internet, it has recently been a critical problem to secure multimedia contents against illegal use. In order to solve this problem, data hiding has drawn great attention as a promising method that plays a complementary role to conventional cryptographic techniques. The idea of this approach is found in ancient Greek literature as 'Steganography,' which means a 'covered writing' for special secret communication. This paper presents a new method for steganographic image transformation, which is different from conventional data hiding techniques. The transformation is achieved in frequency domain and the concept of Fourier filtering method is used. An input image is transformed into a fractal image, which can be used in Computer Graphic (CG) applications. Unauthorized users will not notice the 'secret' original image behind the fractal image, but even if they know that there is a hidden image it will be difficult for them to estimate the original image from the transformed image. Only authorized users who know the proper keys can regenerate the original image. The proposed method is applicable not only as a security tool for multimedia contents on web pages but also as a steganographic secret communication method through fractal images.
This paper presents a restoration scheme of gray level image which can generated more smooth-dithered and less blurred image. Our scheme embeds local area information on each dithering block into the image to get a high quality image. When a dithered image is sent for facsimile in this scheme, the received image can be output as a normal hardcopy and be displayed on the terminal CRT as more clearly softcopy, using the embedded information.
A secret transmission method of character data is presented in this paper when a series of motion pictures are communicated between two stations. Character data are embedded into the codes of image data to be output from the interframe DPCM encoder, so as to prevent a third party from reading the message; The received data are normally decoded to a picture in higher quality and the message is also decoded at the same time if the receiver knows how to embed it. It results in our experiments that the transmission of character data has little effect on picture quality and the amount of embedded characters will be estimated to be about 20 ~ 30% of bits transmitted in each frame, for
example, when SNR is above 30dB.