• 대한전자공학회논문지SP
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• 제41권6호
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• pp.195-208
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• 2004

히스토그램은 여러 가지 응용적인 측면에서 매우 유용한 방법이며, 단순한 계산법과 편리성이 강조되면서, 오늘날 디지털 이미지 프로세싱에서는 기본적인 방법이 되었다. 하지만 히스토그램을 사용하는 방법의 근본적인 한계점은 영상에서 픽셀의 공간적인 위치 정보를 없애 버린다는 것이다. 본 논문은 공간적인 위치정보를 포함한 히스토그램(공간 히스토그램)을 제시하여 영상을 재해석한다. 또한 그 결과를 이용하여 레벨 순서별 Recursive 메디안 필터를 구현 하였다. 제안한 Recursive 메디안 필터는 기존의 Recursive 메디안 필터와 비교 했을 때, 에지 보존 측면에서 상당 부분 개선된 결과를 보였다.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2019년도 제59차 동계학술대회논문집 27권1호
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• pp.83-86
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• 2019

Histogram equalization is extensively used for image contrast enhancement in various applications due to its effectiveness and its modest functions. In image research, image enhancement is one of the most significant and arduous technique. The image enhancement aim is to improve the visual appearance of an image. Different kinds of images such as satellite images, medical images, aerial images are affected from noise and poor contrast. So it is important to remove the noise and improve the contrast of the image. Therefore, for this purpose, we apply a median filter on MR image as the median filter remove the noise and preserve the edges effectively. After applying median filter on MR image we have used intensity transformation function on the filtered image to increase the contrast of the image. Than applied the histogram equalization (HE) technique on the filtered image. The simple histogram equalization technique over enhances the brightness of the image due to which the important information can be lost. Therefore, adaptive histogram equalization (AHE) and contrast limited histogram equalization (CLAHE) techniques are used to enhance the image without losing any information.

• 한국멀티미디어학회논문지
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• 제18권6호
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• pp.691-700
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• 2015

Here, we present a new framework for histogram equalization in which both local and global contrasts are enhanced using neighborhood metrics. When checking neighborhood information, filters can simultaneously improve image quality. Filters are chosen depending on image properties, such as noise removal and smoothing. Our experimental results confirmed that this does not increase the computational cost because the filtering process is done by our proposed arrangement of making the histogram while checking neighborhood metrics simultaneously. If the two methods, i.e., histogram equalization and filtering, are performed sequentially, the first method uses the original image data and next method uses the data altered by the first. With combined histogram equalization and filtering, the original data can be used for both methods. The proposed method is fully automated and any spatial neighborhood filter type and size can be used. Our experiments confirmed that the proposed method is more effective than other similar techniques reported previously.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.835-836
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• 2008

This paper presents a new method of segmenting characters in a car licence plate which is less influenced by illumination variation. It uses an anisotropic filter to reduce the lighting noise and a histogram specification scheme to obtain the binary image. Anisotropic smoothing filter process the input images, which are acquired under different lighting conditions, so that they may have similar image quality. The enhanced performance of the proposed algorithm has been proved by the experiment.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.531-534
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• 2008

Image Hash specifies as a descriptor that can be used to measure similarity in images. Among all image Hash methods, histogram based image Hash has robustness to common noise-like operation and various geometric except histogram _equalization. In this_paper an improved histogram based Image Hash that is using "Imadjust" filter I together is proposed. This paper has achieved a satisfactory performance level on histogram equalization as well as geometric deformation.

• Journal of information and communication convergence engineering
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• 제8권1호
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• pp.112-115
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• 2010

The heart rate is the most important vital sign in diagnosing heart status. The simple method to measure the heart rate in the mobile healthcare device is using the PPG signal. In developing the mobile healthcare device using the PPG signal, the most important issue is the inaccuracy of the measured heart rate because the PPG signal is distorted from the user's motions. To improve the problem, this study proposed the new method that is to estimate the heart rate without an additional sensor in real life. The proposed method in this study is using the histogram filter. In order to evaluate the performance of the proposed method, the study compares its results with the moving average method in motion environment. According to the experimental results, the performance of the proposed method was more than 40% better than the performances of the MAF.

• 한국컴퓨터정보학회논문지
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• 제21권11호
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• pp.23-30
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• 2016

In this paper, we propose an adaptive histogram projection technique for dynamic range compression and an efficient detail enhancement method which is enhancing strong edge while reducing noise. First, The high dynamic range image is divided into low-pass component and high-pass component by applying 'guided image filtering'. After applying 'guided filter' to high dynamic range image, second, the low-pass component of the image is compressed into 8-bit with the adaptive histogram projection technique which is using global standard deviation value of whole image. Third, the high-pass component of the image adaptively reduces noise and intensifies the strong edges using standard deviation value in local path of the guided filter. Lastly, the monitor display image is summed up with the compressed low-pass component and the edge-intensified high-pass component. At the end of this paper, the experimental result show that the suggested technique can be applied properly to the IR images of various scenes.

• 반도체디스플레이기술학회지
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• 제16권2호
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• pp.106-109
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• 2017

Recently, ancient documents are actively studied and discussed. However, ancient documents has a few problems on interpretation. The antique documents are too fragile to hand over. So, some studies have been carried out using terahertz to read ancient documents without damaging them. Three techniques are necessary to read letters using terahertz. First, PPEX algorithm, which distinguishes pages. Second, TGSI technique, which distinguishes text from paper on a page. Third, CCSC algorithm, which transforms signals to letters. In this paper, we will describe the preprocessing process to facilitate the recognition of letters before applying the post processing as we mentioned above. Histogram equalization, Histogram stretching and the Sobel filter were applied to the preprocessing.

• 한국멀티미디어학회논문지
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• 제22권9호
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• pp.983-991
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• 2019

Histogram equalization method is a popular contrast enhancement technique. However, there are some drawbacks, namely, over-enhancement, under-enhancement, structure information loss, and noise amplification. In this paper, we propose an edge-enhancing histogram equalization algorithm while suppressing over-enhancement simultaneously. Firstly, over-enhancement is suppressed by clipping a transfer function, then, edge enhancement is achieved by using guided image filter. Experiments are carried out to evaluate the performance of the various HE algorithms. As a result, both qualitative and quantitative assessment showed that the proposed algorithm successfully suppressed over-enhancement while enhancing edges.

• Journal of information and communication convergence engineering
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• 제13권4호
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• pp.264-269
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• 2015

The chest X-ray image cannot be focused in the same manner that optical lenses are and the resultant image generally tends to be slightly blurred. Therefore, the methods to improve the quality of chest X-ray image have been studied. In this paper, the inherent noises of the input images are suppressed by adding the Laplacian image to the original. First, the chest X-ray image using an Gaussian high pass filter and an optimal high frequency emphasis filter has shown improvements in the edges and contrast of flat areas. Second, using fuzzy logic_histogram equalization, each pixel of the chest X-ray image shows the normal distribution of intensities that are not overexposed. As a result, the proposed method has shown the enhanced edge and contrast of the images with the noise canceling effect.