• 전자공학회논문지B
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• 제32B권12호
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• pp.1614-1623
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• 1995

In this paper we propose a region-adaptive CELP image coder for still images at low bit rates below 0.5 bpp. The proposed method partitions the image into stochastically similar regions by the minimum spanning tree method and finds prediction coefficients for each region using a 2- dimensional linear prediction model. Coding is carried out on 8$\times$8 blocks and when there are several regions included in a block, an image is synthesized using the prediction coefficients of each region. Computer simulation results show that the proposed method allows improved synthesized image over conventional block-adaptive CELP methods, especially at edges. In addition, performance comparison with the JPEG DCT method shows that while the JPEG method shows block distortion and staircase effects (ragged edges) at bit rates below 0.5 bpp, the proposed CELP method shows improved synthesized images with such effects reduced.

• 전자공학회논문지B
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• 제31B권10호
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• pp.99-111
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• 1994

A motion picture compression scheme using subband coding with motion compensation is presneted in this paper. A hierarchical subband decomposition is used to split the image signal into 10 subbands with a 3-layer pyramid structure and motion compensation is used in each band. However, in this case, motion vector information is drastically increased; therefore, initial motion vectors are estimated in the highest pyramid and motion vectors are refined using the reconsructed subband signal in each layer. Simulation results show that the proposed method compares favorably in terms of prediction error energy and side informatio with methods requiring additional information. Images recostructed from the proposed method show good quality compared to those reconstructed using blockwise DCT.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.46-49
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• 2000

An iterative deblocking algorithm for DCT-compressed images using two-dimensional FIR filters adapted for local directionality of each block, is proposed. First, we introduce a set of simple lowpass filters, which are adapted for edges of different angles. In conventional deblocking methods based on lowpass-filtering and convex projections, a single filter is applied to a whole image. In the proposed method, on the other hand, a suitable filter is chosen out of the directional filters designed previously in every subimage (typically $8{\times}8$ block). Experimental results indicate that adaptive filtering improves PSNR at each iteration.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.827-830
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• 2000

In this paper, we propose the method using PCA(principal component analysis) algorithm when proposed algorithm performs multimedia information indexing. After we extract DC coefficients of DCT from MPEG video stream which is an international standard of moving picture compression coding, we apply PCA algorithm to image made of DC coefficients and extract the feature of each DC image. Using extracted features, we generate codebook and perform multimedia information indexing. The proposed algorithm Is very fast when indexing and can generate optimized codebook because of using statistical feature of data

• 한국멀티미디어학회논문지
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• 제22권5호
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• pp.527-534
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• 2019

Recently, Photo editing softwares such as digital cameras, Paintshop Pro, and Photoshop digital can create counterfeit images easily. Various techniques for detection of tamper images or forgery images have been proposed in the literature. A form of digital forgery is copy-move image forgery. Copy-move is one of the forgeries and is used wherever you need to cover a part of the image to add or remove information. Copy-move image forgery refers to copying a specific area of an image itself and pasting it into another area of the same image. The purpose of copy-move image forgery detection is to detect the same or very similar region image within the original image. In this paper, we proposed fast detection of forgery image using four step search based on discrete cosine transform and a four step search algorithm using discrete cosine transform (FSSDCT). The computational complexity of our algorithm reduced 34.23 % than conventional DCT three step search algorithm (DCTTSS).

• 전자공학회논문지B
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• 제33B권11호
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• pp.44-52
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• 1996

This paper proposes a KLT-CVQ scheme using PCNN to improbe the quality of the reconstructed images at a given bit rate. By using the PCNN and classified vector quantization, we exploit the high energy compaction and compelte decorrelation capbilities of the KLT, and the pdf (probability density function) shape and space-filling advantages of the vQ to improve the performance of the proposed hybrid coding technique. In order to preserve the preceptual fetures such as the edge components in the reconstructed images, we classified the input image blocks according to the texture energy measures of the local statistics and vector-coded them adaptively, and thereby reduces the possible edge degradation in the reconstructed images. The results of the computer simulations show that the performance of the proposed KLT-CVQ is higher than that of the KLT-CSQ or the DCT-CVQ in the quality of the reconstructed images at a given bit rate.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1996년도 학술대회
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• pp.159-163
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• 1996

In this paper, a new image compression technique, which uses lifting scheme and pyramid vector quantization, is proposed. Lifting scheme is a new technique to generate wavelets and to perform wavelet transform, and pyramid vector quantization is a kind of vector quantization which dose not have codebook neither codebook generation algorithm. For the purpose of realizing more compression rate, an arithmetic entropy coder is used. Proposed algorithm is compared with other wavelet based image coder and with JPEG which uses DCT and adaptive Huffman entropy coder. Simulation results showed that the performance of proposed algorithm is much better than that of others in point of PSNR and bpp.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.175-177
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• 2004

The current JPEG-2000 standard is a wavelet based scheme because wavelet transform have some advantages compare to DCT transform. In compressed images, there are some image degradation factors like contrast distortion by Quantization process. This factor is very important to HVS (Human Visual System). Therefore, In this paper, we propose a new algorithm for contrast enhancement using the properties of wavelet coefficients. This algorithm is processed in the wavelet domain and so it can be applied efficiently to JPEG-2000.

• 한국정밀공학회지
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• 제22권9호
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• pp.99-106
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• 2005

In recent years, vision sensors are widely used to mobile robot for navigation or exploration. The analog signal transmission of visual data being used in this area, however, has some disadvantages including noise weakness in view of the data storage. A large amount of data also makes it difficult to use this method for a mobile robot. In this paper, a digital data compressing technology based on MPEG4 which substitutes for analog technology is proposed to overcome the disadvantages by using DWT(Discreate Wavelet Transform) instead of DCT(Discreate Cosine Transform). The TI Company's DSP chip, TMS320C6711, is used for the image encoder, and the performance of the proposed method is evaluated by PSNR(Peake Signal to Noise Rates), QP(Quantization Parameter) and bitrate.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권7호
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• pp.302-307
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• 2002

Digital watermarking is the technique, which embeds an invisible signal including signal including owner identification and copy control information into multimedia data such as audio, video, and images for copyright protection. A new MPEG watermark embedding algorithm using complex block effect based on the Human Visual System(HVS) is introduced in this paper. In this algorithm, $8{\times}8$ dark blocks are selected, and the watermark is embedded in the DC component of the discrete cosine transform(DCT) by using quantization and modulus calculation. This algorithm uses a blind watermark retrieval technique, which detects the embedded watermark without using the original image. The experimental results show that the proposed watermark technique is robust against MPEG coding, bitrate changes, and various GOP(Group of Picture) changes.