• ETRI Journal
• /
• 제39권1호
• /
• pp.76-86
• /
• 2017

In this study, we propose an automatic contrast enhancement method based on transfer function modification (TFM) by histogram equalization. Previous histogram-based global contrast enhancement techniques employ histogram modification, whereas we propose a direct TFM technique that considers the mean brightness of an image during contrast enhancement. The mean point shifting method using a transfer function is proposed to preserve the mean brightness of an image. In addition, the linearization of transfer function technique, which has a histogram flattening effect, is designed to reduce visual artifacts. An attenuation factor is automatically determined using the maximum value of the probability density function in an image to control its rate of contrast. A new quantitative measurement method called sparsity of a histogram is proposed to obtain a better objective comparison relative to previous global contrast enhancement methods. According to our experimental results, we demonstrated the performance of our proposed method based on generalized measures and the newly proposed measurement.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권7호
• /
• pp.3401-3420
• /
• 2018

Pixel expansion and contrast are two major performance parameters for visual cryptography scheme (VCS), which is a type of secret image sharing. Random Grid (RG) is an alternative approach to solve the pixel expansion problem. Chen and Tsao proposed the first (k, n) RG-based VCS, and then Guo et al., Wu et al., Shyu, and Yan et al. significantly improved the contrast in recent years. However, the investigations on improving the contrast of threshold RG-based VCS are not sufficient. In this paper, we develop a contrast-improved algorithm for (k, n) RG-based VCS. Theoretical analysis and experimental results demonstrate that the proposed algorithm outperformers the previous threshold algorithms with better visual quality and a higher accuracy of contrast.

• IEIE Transactions on Smart Processing and Computing
• /
• 제3권6호
• /
• pp.358-365
• /
• 2014

This paper proposes a method that reduces the flickering effect caused by A-GLG (Adaptive Gray-Level Grouping) during video contrast enhancement. Of the GLG series, A-GLG shows the best contrast enhancement performance. The GLG series is based on histogram grouping. Histogram grouping is calculated differently between the continuous frames with a similar histogram and causes a subtle change in the transformation function. This is the reason for flickering effect when the video contrast is enhanced by A-GLG. To reduce the flickering effect caused by A-GLG, the proposed method calculates a modified transformation function. The modified transformation function is calculated using a previous and current transformation function applied with a weight separately. The proposed method was compared with A-GLG for flickering effect reduction and video contrast enhancement. Through the experimental results, the proposed method showed not only a reduced flickering effect, but also video contrast enhancement.

• 감성과학
• /
• 제2권1호
• /
• pp.113-119
• /
• 1999

brightness와 contrast의 적절한 조절은 자연색 재현 및 다양한 분위기 창출이 가능하여 디스플레이의 질을 향상시킬 수 있다. 디스플레이 사용자들은 OSD(On-Screen-Display)를 통해 brightness와 contrast상태를 임의로 조절할 수 있으나, 조절에 따른 영상의 변화를 예측하지 못하므로 이를 잘 활용하지 못하고 있다. 본 연구에서는 brightness와 contrast가 각각 영상에 미치는 영향을 분석하여 자연색 재현이 가능한 최적상태와 4가지의 감성적 분위기를 나타낼 수 있는 조절상태를 정의하였다. 5가지 조절상태를 OSD에 제시함으로써 사용자가 쉽게 영상의 이미지에 적합한 brightness와 contrast상태로 조절할 수 있어 제품에 대한 만족감을 높일 수 있는 brightness/contrast 통함 조절방법을 제안하였다.

• 복식
• /
• 제60권1호
• /
• pp.28-42
• /
• 2010

A purpose of this study is to 6nd out how the casual and formal style clothes of stripe pattern giving variety by pattern direction, pattern width, and contrast coloration have an effect on image of wearers. For this, 192 stimuli were made and 1200 testee evaluated them using semantic differential scale. As a result, five image dimensions were drawn as a factor of attractiveness, gracefulness, activeness, visibility, and tenderness. Unlike the value contrast previously researched, it showed that chroma contrast coloration which was interacted with a color tone contrast coloration had an effect on all the 5 image dimensions. This result was recognized as significant clothes dues in evaluating the image of stripe wearers. Besides, clothing style, stripe pattern, and contrast coloration were made clear as an efficient parameter in image presentation of clothing wearers.

• Journal of Magnetics
• /
• 제21권2호
• /
• pp.281-285
• /
• 2016

The purpose of study was to evaluate SNR and CNR with different contrast agent contents (1.0 mmol/mL gadobutrol and 0.5 mmol/mL gadoterate meglumine) for spin echo (SE) and 3-dimension contrast-enhanced fast field echo (3D CE-FFE) pulse sequences. In this study, we compared the SNR and the CNR between 0.5 mmol/mL gadoterate meglumine and 1.0 mmol/mL gadobutrol according to the concentration of contrast agent in brain MRI. When we compared between SE and 3D CE-FFE pulse sequences, the higher SNR and CNR using 3D CE-FFE pulse sequence can be acquire regardless of contrast agent contents. Also, a statistically significant difference was found for SNR and CNR between all protocols. In conclusion, our results demonstrated that the SNR and CNR have not risen proportionately with contrast agent contents. We hope that these results presented in this paper will contribute to decide contrast agent contents for brain MRI.

• Journal of the Optical Society of Korea
• /
• 제12권4호
• /
• pp.319-325
• /
• 2008

We propose a phase contrast filter using photopolymer, for the phase contrast projection display. The photopolymer has high photosensitivity such that its optically induced refractive index change has a linear dependency on the illuminating light intensity. We implemented a phase contrast projection display using photopolymer as a phase contrast filter. By controlling the refractive index change of the photopolymer, we successfully convert an input phase image into a high contrast intensity image. We also investigated the effect of the photopolymer illumination condition on the quality of the displayed intensity image. As a projector, we achieved 82% phase to intensity conversion efficiency, which implies that the proposed method can potentially have much higher light efficiency than conventional projection display.

• Investigative Magnetic Resonance Imaging
• /
• 제23권1호
• /
• pp.17-25
• /
• 2019

We discuss recent advances in Gd-based $T_1$-weighted MR contrast agents for the mapping of cellular pH. The pH plays a critical role in various biological processes. During the past two decades, several MR contrast agents of strategic importance for pH-mapping have been developed. Some of these agents shed light on the pH fluctuation in the tumor microenvironment. A pH-responsive self-assembled contrast agent facilitates the visualization of tumor size as small as $3mm^3$. Optimization of various parameters is crucial for the development of pH-responsive contrast agents. In due course, the new contrast agents may provide significant insight into pH fluctuations in the human body.

• Clinical Pain
• /
• 제20권2호
• /
• pp.86-92
• /
• 2021

Ultrasound imaging in clinical practice is one of the widely used diagnostic methods because there is no radiation risk, more cost- effective compared to MRI or CT, and possible to perform an intervention through fast real-time imaging. In order to increase the diagnostic value, the studies of contrast-enhanced ultrasound (CEUS) using an ultrasound contrast agent have been actively conducted since about 50 years ago and are being used clinically in vascularity and microcirculation of internal organs. Although ultrasound is actively used for the diagnosis and treatment of various diseases in musculoskeletal disorders, there are some limitations in diagnosing mild or small lesions, inflammatory reactions, or abnormalities at the molecular level. In this review, the principles, types, and research, and clinical applications of ultrasound contrast agents have been summarized and introduced. If we understand the characteristics of the ultrasound contrast agents and anatomical knowledge, as well as molecular changes, the ultrasound contrast agents are widely applied in musculoskeletal disorders and have tremendous potential for diagnosis and treatment.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
• /
• pp.1139-1142
• /
• 2007

In this paper, an image enhancement method by saturation and contrast improvement is proposed. Histogram equalization with color difference makes higher contrast. By generating saturation amplification ratio with color difference, the saturation improves effectively. The experimental results show that the proposed algorithm has higher contrast and more natural - look than the conventional methods.