• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1434-1440
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• 2014

This paper describes a demosaicking method for hexagonally-structured color filter array. Demosaicking is essential to acquire color images using color filter array (CFA) in single sensor imaging. Thus, CFA patterns have been discussed in order to improve image quality in single sensor imaging after the Bayer pattern are introduced. Advancements in imaging sensor technology recently introduce a hexagonal CFA pattern. The hexagonal CFA can be considered to be a 45-degree rotational version of the Bayer pattern, thus demosaicking can be implemented by an existing method with backward and forward 45-degree rotations. However, this approach requires heavy computing power and memory in image sensing devices because of the image rotations. To overcome this problem, we proposes a demosaicking method for a hexagonal Bayer CFA without rotations. In addition, we introduce a weighting parameter in our demosaicking method to improve image quality and to unifying exiting method with our method. Experimental results indicate that the proposed method is superior to conventional methods in terms of PSNR. In addition, some optimized values for the weighting parameter are provided experimentally.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5C
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• pp.286-294
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• 2011

In most digital cameras, images are obtained by a sensor overlaid by the color filter array (CFA) such as Bayer, demanding a demosaicking procedure to rebuild the full resolution color images. However, due to the nature of sensor, it is necessary to consider denoising step to remove the noise. In this paper, we analyze demosaicking and denoising jointly and show that the proposed method can solve the denoising issue by simple manner, well suppress different level of noises. The proposed algorithm yields comparable performances measured by several image quality assessment (CPSNR, SCIELAB, and FSIM), while the computational cost is low.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.265-279
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• 2010

A color image requires at least three color channels to obtain the full color image. However the image sensor obtains only the intensity of the brightness, that is, three image sensors are required for every pixel to capture the full color image. Since the image sensor is quiet expensive, most of digital still cameras adopt single image sensor array with color filter array (CFA) to reduce the size and the cost. Since the image obtained using single sensor array has only one color component per pixel, we need to reconstruct the missing two color components to obtain the full color image. We call this process as color filter interpolation or demosaicking. In this paper, demosaicking algorithm composed of two large step is proposed. Proposed algorithm is combined with several different algorithms such as Edge-directed demosaicking, Second-order gradients as correction terms, Smooth hue transition Interpolation, etc. The simulation results show that the proposed algorithm performs much better than the state-of-the-art demosaicking algorithms in terms of both subjective and objective qualities.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1276-1282
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• 2013

This paper presents a demosaicking method based on high-order interpolation with parameters. Demosaicking is an essential process in capturing color images through a single sensor-array. Thus, a lot of methods including the Hamilton-Adams(HA) method has been studied in this literature. However, the image quality depends on various factors such as contrast and correlation in color space; existing algorithms depend on test images in use. Consequently, a new test image set was suggested to develop demosaicking algorithms properly. According to previous studies, the HA method shows high performances with the new test data set. In this paper, we improve the HA method using high-order interpolation with parameters. Also, we provide an analysis and formulations for the proposed method. To evaluate our method, we compare our method with the existing methods both objectively and subjectively. The experimental results indicate that the proposed method is superior to the existing methods.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.11a
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• pp.205-207
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• 2009

디지털 카메라를 이용한 영상 취득은 일반적으로 한 픽셀에서 세 가지 색상(적색, 녹색, 청색)의 값을 얻는 것을 목표로 한다. 하지만, 비용의 문제로 한 픽셀에서 한 가지의 색상만을 얻어 나머지 두 색상을 복원하는 방식을 널리 사용한다. 이를 demosaicking이라 하는데, 이 과정에는 1)각 색상 영상 내의 상관관계와 2)세 가지 색상 사이의 상관관계가 동시에 이용된다. 본 논문에서는 이 두 가지 상관관계를 이용하여 각 채널의 고주파 성분과 밝기 성분의 고주파 성분을 반복적으로 향상시키는 방법을 제안하였다. 첫 번째 단계에서는 밝기 성분을 이용하여 각 채널의 고주파 성분을 강화하고, 두 번째 단계에서 관측값을 이용하여 밝기 성분의 고주파 성분을 복원한다. 제안된 방법이 기존 방법과 주관적인 방법과 객관적인 방법으로 비교하여 우수함을 보인다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.4
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• pp.41-48
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• 2010

In this paper, we present an efficient demosaicking method using the difference between color channels in the wavelet domain. In our method, the low frequency wavelet coefficients are obtained by an edge-directive interpolation using the observed high frequency coefficients. The missing high frequency coefficients are obtained by the estimated low frequency coefficients. In order to reduce artifacts in high frequency domain and to improve visual quality, we update the high frequency coefficient using the color difference rule in the wavelet domain. We simulate our demosaicking method in the wavelet domain and compare our algorithm to the existing demosaicking schemes. Experimental results illustrate that the proposed method can generate enhanced demosaicking results.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.3
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• pp.46-54
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• 2008

Most commercial CCD/CMOS image sensors have CFA(Color Filter Array) where each pixel gathers light of a selective color to reduce the sensor size and cost. There are many algorithms proposed to reconstruct the original clolr image by adopting pettern recognition of regularization methods to name a few. However the resulting image still suffer from errors such as flase color, zipper effect. In this paper we propose an adaptive edge weight demosaicking algorithm that is based on POCS(Projection Onto Convex Sets) not only to improve the entire image's PSNR but also to reduce the edge region's errors that affect subjective image quality. As a result, the proposed algorithm reconstruct better quality images especially at the edge region.

• Journal of the Korea Society of Computer and Information
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• v.22 no.11
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• pp.25-30
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• 2017

In this paper, We proposed an effective demosaicking method for single chip RGB-NIR sensors to recover RGB and NIR images. As the method operates in the spatial frequency domain, the frequency domain characteristics of the sampled CFA data are investigated. Using the luminance signal in the frequency domain and the chrominance signals are processed separately with different filters. The simulated images using the real images are compared with other state-of-art methods. As a result, the proposed demosaicking method resulted an effective calculation by a single processing which the existing alternating projection method requires repeated calculation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.344-349
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• 2012

This paper describes experimental results and their analysis on the new test images, called as the McMaster image dataset, to develop demosaicking techniques. The well-known image dataset for demosaicking is so far the Kodak image dataset. However, different results have been reported, as the new image dataset is engaged in developing demosaicking techniques. Thus, we conduct a series of experiments on both the McMaster dataset and the Kodak dataset; we analyze and compare those experimental results; and we provide the peculiar features of the new dataset. Also, the experimental results and their analysis indicate that the McMaster dataset deserves to be a test image dataset for future demosaicking techniques; thus, we expect they can be utilized as basic data for demosaicking.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12C
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• pp.1004-1009
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• 2010

ost digital cameras use single sensor array with color filter array to reduce size and cost. However images taken by single sensor array have only one color component per pixel, to obtain a color image missing two color components need to be reconstructed. This reconstructing process is called as demosaicking. This paper propose a new directional demosaicking method and proposed method achieves better image quality with enhanced weighting function. With comparing objective and subjective performance, we show proposed method achieves better performance than the conventional methods.