• Journal of Korea Multimedia Society
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• v.1 no.2
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• pp.183-193
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• 1998

Color inverse halftoning is the transformation of a color-halftone image to a continuous-tone color image that is more natural in human vision. In this paper, we propose a new smoothing mask that can remove halftone patterns in channel effectively and we apply it to color inverse halftoning. The proposed smoothing mask can make channel images more smooth and natural in human vision than traditional ones. Its characteristic can be adapted automatically according to the various color halftone images. We analyze the result images in various aspects through experiments. Experimental results show that the mask is useful for color inverse halftoning. It can be applied to field of multimedia application, such as desktop publishing, color facsimile and digital library construction.

• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.221-228
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• 2005

The paper proposes the improved error diffusion halftoning system to enhance the edges using the spatial perceptual characteristics of the human visual system. The proposed method computes a spatial variation(SV), which is the difference between a pixel luminance and the average of its $3{\times}3$ neighborhood pixels' luminances weighted according to the spatial positioning. Information of edge enhancement(IEE) Is computed using the SV and the local average luminance. The IEE is added to the quantizer's input pixel and feeds into the halftoning quantizer. The quantizer produces the halftone image having the enhanced edge. The performance of the proposed method is compared with conventional methods by measuring the edge correlation. The halftone images by using the proposed method show better quality due to the enhanced edge. And the detailed edge is preserved in the halftone images by using the proposed method.

• 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 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.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.851-854
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• 2000

Digital halftoning is a technique to make an equivalent binary image from scanned photo or graphic images. Low pass filtering characteristic of human visual system can be applied to get the effect of spatial averaging of local area consisted of black and white pixels for gray image. The overlapping of black dot decreases brightness and black dot is very sensitive to human visual system in the bright region. In this paper, for gray-level expression, only bright gray region in the color image is considered for blue noise mask (BNM) approach. To solve this problem, BNM with CMY dot is used for the bright region instead of black dot. Dot-on-dot model with single mask causes the problem making much black dot overlap, color distortion. Therefore approach with three masks for C, M and Y each is proposed to decrease pixel overlap and color distortion.

• Journal of the Korean Graphic Arts Communication Society
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• v.15 no.2
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• pp.15-24
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• 1997

In DTP systems, satisfactory matching the appearance of displayed image on CRT and that of a reproduced binary image is very important. Most halftoning techniques assume that the printed color dots are square. However, most printers produce roughly circular dots. Thus, there is overlap between adjacent dots, and dots accupy adjcent space that should be empty space. These results are because the significant image distortion on the reproduced images. In this paper, we proposed a new tone correction digital halftoning method based on equi-visual perception characteristic.

• Proceedings of the Korea Multimedia Society Conference
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• 1998.04a
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• pp.148-153
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• 1998

칼라 역 해프토닝(Color inverse halftoning)은 해프토닝 칼라 영상을 시각적으로 보다 자연스러운 연속계조 칼라영상으로 변환해 주는 방법이다. 본 논문에서는, 분리된 각 칼라 채널 영상에서 나타나는 해프톤 셀 패턴을 효과적으로 제거할 수 있는 새로운 평활화 마스크를 제안하고, 이를 칼라역 해프토닝에 활용하였다. 제안한 평활화 마스크는 기존의 평활화 마스크가 잘 제거하지 못했던 해프톤, 셀 패턴을 시각적으로 보다 자연스럽게 평활해 줄 수 있으며, 마스크의 특성을 평활화하고자 하는 채널 영상에 적합하게 조정할 수 있도록 설계하였다. 실험을 통해, 평활화된 채널 영상과 그 스펙트럼을 비교 분석함으로써 제안한 방법의 유용성을 확인하였다. 이 방법은 전자 출판, 칼라 팩스, 해프톤 영상의 압축 등의 분야에 활용될 수 있다.

• Proceedings of the Korea Multimedia Society Conference
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• 1998.10a
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• pp.260-265
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• 1998

칼라 역 헤프토닝(Color inverse halftoning)은 헤프토닝된 칼라 영상을 시각적으로 보다 자연스러운 연속계조 영상으로 변환해 주는 방법이다. 본 논문에서는, 칼라 채널 영상에서 나타나는 모아레 페턴을 효과적으로 제거하면서 경계를 보존할 수 있는 적응적 평활화(adaptive smoothin) 방법을 제안하였다. 적응적 평활화 방법은 해프톤 영상을 블록으로 나눈 후, 각 블록에서의 모아레 패턴이 존재하는 정도를 나타내는 모아레 가중치 값을 계산하고, 이 값에 다라 평활화 정도를 조절한다. 실험을 통해 제안한 방법이 경계를 효과적으로 보존하면서도 모아레 패턴을 효과적으로 제거할 수 있음을 확인하였다. 제안한 방법은 전자 출판, 칼라 팩스, 해프톤 영상의 압축, 디지털 도서관 구축 등과 간은 멀티미디어 응용 분야에서 유용하게 활용할 수 있다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.208-217
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• 2001

Model-based color image halftoning method using dot-pattern database is proposed for low-resolution color image printing. Dot-pattern database used in the proposed method is based on Blue-Noise Mask. The database consists of dot-patterns constructed by circular dot-overlap model according to each color value. In halftoning procedure, input color value is reproduced as the dot-pattern selected to minimize the difference between the color values of the original image and those of the printed image. Also, the contrast sensitivity function as a human visual model is used to improve the perceived quality of the printed image in dot-pattern selection. Thus, the proposed method can substantially reproduce the color values of the pixels in original image and obtain better image quality. In the experiment, the proposed method has less ΔΕ/Sub ab/ between the original image in monitor and the printed one than that of ED and BNM halftoning. This result approves that the proposed method reproduces better image quality.