• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.134-136
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• 2015

영상 역 하프토닝은 입력된 하프톤 영상으로부터 그레이 영상을 복원시키는 것으로, 하프톤 영상으로 처리하지 못하는 다양한 영상처리를 가능하게 해주는 방법이다. 기존의 참조표를 이용한 역 하프토닝 방법은 다양한 하프톤 영상과 원본 그레이 영상으로부터 추출한 정보를 이용해 입력 영상을 복원시키는데, 본 논문에서는 이를 바탕으로 하여 영상의 질을 전반적으로 향상시킬 수 있는 국부적인 이진 패턴 기반 참조표를 이용한 영상 역 하프토닝 방법을 제안한다. 먼저 참조표를 이용한 역하프토닝 방법을 이용해 영상을 복원한 후 각 픽셀에서의 국부 이진패턴을 계산하여 각 픽셀 값을 패턴에 따라 분류한다. 분류된 패턴 정보에 따라 국부 이진 패턴 기반 참조표를 생성하고 이를 통해 입력 하프톤 영상에 대한 역 하프토닝을 수행한다. 실험 결과는 제안하는 알고리즘이 오류 확산법에 의해 변환된 하프톤 이미지를 역 하프토닝 했을 때, 기존의 역 하프토닝 방법에 비해 더 나은 PSNR을 달성하는 것을 보인다.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.648-653
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• 2018

Analysis of a specific wavelength band of a video signal is an old research field. However, studies on the analysis of signals having the characteristics of a specific wavelength band or the generation of samples have been conducted actively in recent years. In this paper, we analyze the signal of digital halftoned image. The interpretation of halftoning in terms of signals was first made by Ulichney. We have come to the view that the signal characteristics between pixels used for half toning are good for blue noise. Lau has developed a halftoning method that uses green-noise characteristics by using output-dependent feedback as an error diffusion method. Jho has developed a method for producing halftoned images using a reaction diffusion model. In this paper, we analyze reaction diffusion halftoning in terms of signal to show green noise and compare it with existing green noise half tone.

• Journal of Digital Convergence
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• v.12 no.1
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• pp.415-421
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• 2014

In this paper, we proposed problem and improvement of halftoning using random space filling curve. Random space filling curve is developed as a solution for shortcoming which space filling curve has self-similarity. It is used to reduce regular pattern can be occurred in constant brightness area in order that randomness apply to scanning path. But there is a problem that some area along scanning path can show too bright result in halftoning using random space filling curve. In this paper, we analyzed cause of problem and proposed single pixel error diffusion as a solution method. This method can avoid over-accumulated error and show better result in halftoning.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.984-990
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• 2009

Halftoning is very important image processing techniques in the digital printing industry which is a process of converting a continuous-tone image to bi-level tone image. In this paper we introduce a new digital halftoning method based on maze generation algorithm as a replacement algorithm of halftoning with space-filling curve. Previous error-diffusion methods based on space-filling curve suffer from regular pattern artifacts from uniform scan pattern. We use maze generation algorithm to remove this undesirable pattern of space-filling curve method.

• Proceedings of the Korea Multimedia Society Conference
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• 2004.05a
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• pp.147-150
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• 2004

워터마킹은 디지털 영상에 저작권 정보를 삽입하여 불법복제를 막는 중요한 기술이다. 지금까지는 주로 온라인 디지털 영상에 대한 워터마크 연구가 주로 이루어져 왔다. 본 논문은 온라인이 아닌 인쇄된 영상에서의 워터마킹 기술을 다룬다. 워터마크 비트에 따라 디더링시 사용하는 임계값 패턴을 다르게 하여 인쇄 영상 안에 워터마크를 삽입한다. 워터마크의 추출은 하프토닝된 인쇄 영상을 역하프토닝하여 원래의 그레이스케일 영상으로 복원한 다음, 워터마크 삽입 때 사용한 여러 개의 디더링 임계값 패턴을 사용하여 디더링한 후, 이 결과를 원래의 하프토닝 영상과 비교하여 가장 많이 일치하는 임계값 패턴을 찾아냄으로써 추출된다. 실험을 통하여 제안된 방법이 기존의 방법보다 워터마크 추출률이 우수하며 스캐너와 프린터의 하드웨어적인 특성을 고려한 공격시에도 더 강인함을 보였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.79-85
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• 2013

In this paper, we discussed the traditional methods of generating digital halftoning image and DCT transform. Then we propose a new and simple halftoning algorithm that is based on DCT transformation. We do the feasibility test to verify the proposed algorithm. So we assessed several images generated by adjusting weights of DCT coefficients. As a result, we got the better result for weights of the ramp function type than for weights of the step function type through experiment. As a simple application, we can apply our algorithm to the MPEG video for generating the halftoning video.

• Journal of KIISE:Software and Applications
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• v.35 no.3
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• pp.162-168
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• 2008

A look-up table based vector adaptive filter is proposed in color inverse halftoning. Inverse halftoning converts halftone image into a continuous-tone image. The templates and training images are required in the process of look-up table based methods, which can be obtained from distributed patterns in the sample halftone images and their original images. Although the look-up table based methods usually are faster and show better performances in PSNR than other methods do, they show wide range of qualities depending on how they treat nonexisting patterns in the look-up table. In this paper, a vector adaptive filter is proposed to compensate for these nonexisting patterns, which achieves better quality owing to the contributed informations about hue, saturation, and intensity of surrounding pixels. The experimental results showed that the proposed method resulted in higher PSNR than that of conventional Best Linear Estimation method. The bigger the size of the template in the look-up table becomes, the more outstanding quality in the proposed method can be obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.72-80
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• 2009

Look-up table based inverse halftoning from the digital color halftone image is proposed in this paper, which uses vector adaptive filter for the nonexisting patterns in the table. Halftone image is obtained from a continuous -tone image, which can be restored into continuous one from the digital binary image by way of inverse halftoning method. Look-up table based method usually processes fast and has even performances over the various halftoning. The numbers of pixels in the pattern of table and the method how to define the table elements for each R, G, B channels can effect largely for its performance. The proposed method uses 16 pixels in the table considering the diversity of the expressions from their patterns and with memory size as well. This also proposed how to combine R, G, B channels into one. Experimental results showed the better performance in the expression of colors, better color restoration and the short processing time compared with the conventional ones.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.4
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• pp.227-236
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• 2003

This paper proposes a modified jointly-blue noise mask (MJBNM) method using the S-CIELAB color measure as digital color halftoning method. Based on an investigation of the relation between the pattern visibility and the chromatic error, of a blue noise pattern, a halftoning method is proposed that reduces the chromatic error, while preserving a high quality blue noise pattern. Accordingly, to reduce the chrominance error, the low-pass filtered error and S-CIELAB chrominance error are both considered during the mask generation procedure and calculated for single and combined patterns. Using the calculated low-pass filtered error, the patterns are then updated by either adding or removing dots from the multiple binary patterns. Finally, the pattern exhibiting the lower S-CIELAB chrominance error is selected. Experimental results demonstrated that the proposed algorithm can produce a visually pleasing half toned image with a lower chrominance error than the JBNM method.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.4
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• pp.20-28
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• 2000

The error diffusion algorithm is good for reproducing continuous image to binary image. However the reproduction of edge characteristic is weak in power spectrum analysts of display error. In this paper, an error diffusion method which include pre-filter algorithm for edge characteristic enhancement is proposed Pre-filter algorithm is organized horizontal and vertical directional differential value and weighting function of pre-filter First, it is obtained the horizontal and vertical differential value from the peripheral pixels in original image using $3{\times}3$ Sobel operator Secondly weighting function of pre-filter is composed by function including absolute value and sign of differential value The improved Error diffusion algorithm using pre-filter, present a good result visually which edge characteristic is enhanced. The difference between orignal image and halftoning image is compared with edge-enhanced error diffusion algorithm by measuring the radially averaged power spectrum density.