• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.2
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• pp.106-113
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• 1998

Quantizer with bit rate control performs lossy compressionin moving image coding. Efficient quantizer can improve subjective quality of reconstructed image at the same bit rate because most of errors are occured at this stage. Although quantization matix of current compression stantards reflects human visual system, the performance of their quantization matrixes is not always optimal because they are not considering each image characteristics. We proposed a new adaptive optimal quantization matrix obtained by considering complexity of each image subblocks. It resulted in improvments of image quality about 0.05-0.82 dB and good subject quality at edge regions when we simulated the quantization method in various coding statndards.

• ETRI Journal
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• v.40 no.5
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• pp.677-686
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• 2018

A novel data hiding technique based on modified histogram shifting that incorporates multi-bit secret data hiding is proposed. The proposed technique divides the image pixel values into embeddable and nonembeddable pixel values. Embeddable pixel values are those that are within a specified limit interval surrounding the peak value of an image. The limit interval is calculated from the number of secret bits to be embedded into each embeddable pixel value. The embedded secret bits can be perfectly extracted from the stego image at the receiver side without any overhead bits. From the simulation, it is found that the proposed technique produces a better quality stego image compared to other data hiding techniques, for the same embedding rate. Since the proposed technique only embeds the secret bits in a limited number of pixel values, the change in the visual quality of the stego image is negligible when compared to other data hiding techniques.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.4
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• pp.198-205
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• 2002

In this paper, we proposed a wavelet image coder based on the portable embedded microprocessor. The proposed coder stores the bit level information of the wavelet coefficient in the 2D significance array. Using this information, the coder make the significance check for coefficient and bit level scanning at the same pass. The proposed method has the advantage that we can reduce the scan iteratively and the memory usage for the coding process. Experimental results show that the proposed method outperforms popular image coders such as JPEG, EZW and SPIHT in based on the portable embedded system environment.

• Journal of Information Processing Systems
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• v.13 no.1
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• pp.114-127
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• 2017

This paper proposes a color image coding algorithm based on shape-adaptive all phase biorthogonal transform (SA-APBT). This algorithm is implemented through four procedures: color space conversion, image segmentation, shape coding, and texture coding. Region-of-interest (ROI) and background area are obtained by image segmentation. Shape coding uses chain code. The texture coding of the ROI is prior to the background area. SA-APBT and uniform quantization are adopted in texture coding. Compared with the color image coding algorithm based on shape-adaptive discrete cosine transform (SA-DCT) at the same bit rates, experimental results on test color images reveal that the objective quality and subjective effects of the reconstructed images using the proposed algorithm are better, especially at low bit rates. Moreover, the complexity of the proposed algorithm is reduced because of uniform quantization.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.06a
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• pp.231-234
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• 2016

본 논문에서는 전송하고자 하는 원영상 대신에 전혀 다른 영상을 전송하여 원영상 정보를 보호하는 스테가노그래피(steganography) 기법을 제안한다. 전송할 영상의 자연스러움을 잃어버리지 않으면서 원영상을 복구할 수 있는 차영상 정보를 LSB(Least Significant Bit)에 담고, 픽셀간의 위치 관계를 무작위로 섞어 줌으로써, 원영상을 보호하는 기법을 제안한다. 본 논문에서는 우선 원영상과 전송할 영상 (cover image)의 차영상을 생성하고, 각 픽셀의 차이값을 큰 범위로 양자화하여 차영상의 데이터 크기를 줄인다. 그리고, 각 픽셀의 차이값을 전송할 영상의 4 픽셀에 걸쳐서 하위 2bit 에 나누어 담는다. 8bit 영상에서 하위 2 bit 를 다루기 때문에, 각 채널 밝기값의 최대 차이값은 3 으로 설정되어 자연스럽게 영상을 생성할 수 있다. 끝으로 신호의 보호를 위하여 차영상의 픽셀과 전송할 영상의 픽셀간의 대응위치를 무작위 순열로 변환하여 외부에서 쉽게 복원할 수 없도록 한다. 이러한 스테가노그래피 제안 기법을 통하여 원영상 대신에 커버 영상을 전송함으로써, 자연스러운 정보전송이 가능하며, 외부의 감시와 복원에 안전한 정보보호 기능이 강화될 수 있다. 여러 영상에 대한 실험을 통한 제안 기법에 의하면, 전송되는 커버 영상이 자연스럽기 때문에 외부에서 정보가 숨겨진 사실을 느끼지 못하며, 송수신 장치에 내장된 무작위 순열을 통하여 외부에서는 원영상 정보를 복구하는 것도 매우 어렵게 되어 있음을 확인하였다. 본 제안 기법은 군사통신이나 중요한 정보를 다루는 기관에서의 정보 전달 및 정보보호 시스템에서 사용될 수 있다.

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.579-587
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• 2008

Typically, the file sizes of JPEG compressed images with various complexity differ from images regardless of same image size. So, it is not easy to estimate the remaining image counts that should be stored in the limited storage equipped with the digital camera. To solve the problem, the bit rate control employs the modification of quantization table. The previous work assumed that there is linear relation between image activity and modification factor of quantization table, but in this paper, more accurate functional relations based on statistics are employed to improve the bit rate control accuracy. Computer simulations reveals that the standard deviation of the bit rate error of the proposed scheme is 50% less than that of the conventional method.

• Journal of IKEEE
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• v.24 no.2
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• pp.507-513
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• 2020

The median filter that is used in various fields requiring image processing converts to a median value of pixels belonging to a radius r for all pixels in the image of n×m size. For 8-bit depth images, an O(nm) time algorithm exists but for over 16-bit depth images, there is an O(nmlog²r) time algorithm of Gil and Werman. In this paper, we propose an efficient median filter algorithm that works for more than 16-bit depth images. The time complexity of our algorithm is the same as that of Gil and Werman, but theoretical analysis and experimental results show that ours is efficient than above two times.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.111-119
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• 1994

In this paper we propose a reversible image coding methods with progressive build-up function by bit-plane of multi-lavel image. Firstly, the differencial conversion is applied to reduce the entropy of source images. Then the bit-plane sequences of converted images are coded by means of the newly designed VFRL(Variable to Fixed Run-Llength) code and the RDHC(Run-length Dynamic Huffman Coding). We aim to the simple construction to reduce the complexity. The computer simulated results show that the proposed methods are very effective to the multi-level digital images. For "GIRL" and "COUPLE" of 1EEE monochromatic standard images, the compressibility are superior to the results obtained by the well-known universal codes.own universal codes.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2629-2639
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• 1997

The video coding for very low bit-rate has recently received considerable attention, but the conventional coding schemes with block based transform suffer from the blocky effect for the constraints of limited bit-rate. In this paper, we present a video coding system based on wavelet transform and multiresolution motion estimation/compensation for very low bit-rate video. The proposed scheme uses the wavelet transform which is flexible to represent non-stationary image signals and adaptable to the human visual characteristics. The wavelet transformed coefficients are coded by various coding modes in accordance with the sum of absolute error after motion estimation/compensation in wavelet decomposed domain. And simple buffer control technique is applied to handle constant image quality. It is shown that the presented scheme has more acceptable image quality without blocky effects than conventional block based transform video coding.

• Journal of Digital Contents Society
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• v.17 no.6
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• pp.593-601
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• 2016

This paper is related to the Region-based Spectral Correlation Estimation(RSCE) coding method that makes it possible to achieve the high-compression ratio by estimating color component images from luminance image. The proposed method is composed of three steps. First, Y/C bit-plane summation image is defined using normalized chrominance summation image and luminance image, and then the Y/C bit-plane summation image is segmented for extracting the shape information of the regions. Secondly, the scale factor and the offset factor minimizing the approximation square errors between luminance image and R, B images by the each region are calculated. Finally, the scale factor and the offset factor for the each region are encoded into bit stream. Referring to the results of computer simulation, the proposed method provides more than two or three times higher compression ratio than JPEG/Baseline or JPEG2000/EBCOT algorithm in terms of bpp needed for encoding two color component images with the same PSNR.