• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.62 no.2
• /
• pp.90-94
• /
• 2013

In this paper, we propose a new algorithm to improve the contrast ratio, to preserve information of bright regions and to maintain the color of backlight image that appears with a great relative contrast. Backlight images of the natural environment have characteristics for difference of local brightness; the overall image contrast improvement is not easy. To improve the contrast of the backlight images, MSR (Multi-Scale Retinex) algorithm using the existing multi-scale Gaussian filter is applied. However, existing multi-scale Gaussian filter involves color distortion and information loss of bright regions due to excessive contrast enhancement and noise because of the brightness improvement of dark regions. Moreover, it also increases computational complexity due to the use of multi-scale Gaussian filter. In order to solve these problems, a linear MSR is performed that reduces the amount of computation from the HSV color space preventing the color distortion and information loss due to excessive contrast enhancement. It can also remove the noise of the dark regions which is occurred due to the improved contrast through edge preserving filter. Through experimental evaluation of the average color difference comparison of CIELAB color space and the visual assessment, we have confirmed excellent performance of the proposed algorithm compared to conventional MSR algorithm.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.12 no.4
• /
• pp.231-238
• /
• 2017

Detecting small infrared targets from the low-SCR images at a long distance is very hard. The previous Local Contrast Method (LCM) algorithm based on the human visual system shows a superior performance of detecting small targets by a background suppression technique through local contrast measure. However, its slow processing speed due to the heavy multi-scale processing overhead is not suitable to a variety of real-time applications. This paper presents a lightweight real-time small target detection algorithm, called by the Improved Selective Local Contrast Method (ISLCM), to reduce the scale-invariant computational overhead. The proposed ISLCM applies the improved local contrast measure to the predicted selective region so that it may have a comparable detection performance as the previous LCM while guaranteeing low scale-invariant computational load by exploiting both adaptive scale estimation and small target feature feasibility. Experimental results show that the proposed algorithm can reduce its computational overhead considerably while maintaining its detection performance compared with the previous LCM.

• Journal of Korea Multimedia Society
• /
• v.21 no.2
• /
• pp.108-116
• /
• 2018

In this paper, we propose an image enhancement method based on Multi-Scale Retinex theory that designs Unsharp Masking Filter (UMF) and emphasizes the contrast ratio adaptively. Unsharp Masking (UM) technique emphasizes image sharpness and improves contrast ratio by adding high frequency component to the original image. The high frequency component is obtained by differentiating between original image and low frequency image. In this paper, we present how to design an UMF kernel and to adaptively apply it to increase the contrast ratio according to multi-scale retinex theory which resembles human visual system. Experimental results show that the proposed method has better quantitative performance indexes such as PSNR, ambe & SSIM and better qualitative feature like halo artifact suppression.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.5
• /
• pp.115-121
• /
• 2007

Phase contrast imaging in atomic force microscopy showed a promise as an effective tool for better understanding of micromechanical properties of surfaces at nano scale. A qualitative estimation model for phase contrast images obtained with a tapping mode AFM was developed. This investigation demonstrated the high efficiency of combined analysis of topography and phase contrast images for characterizing nanosurfaces. Phase contrast images allowed estimation of relative stiffness(elastic modulus) of the sample surface. The phase contrast images revealed a significant inhomogeneity of the nano scale worn surfaces. Phase contrast images are also capable of revealing the formation of tribofilms.

• Journal of the Korean Society of Radiology
• /
• v.18 no.6
• /
• pp.707-713
• /
• 2024

In CT equipments, the contrast scale changes as the equipment ages. In order to maintain a constant contrast scale in clinical practice, users must perform periodic quality control. In this study, the contrast scale for each effective photon energy was determined and analyzed based on CT slice images of the CT number calibration block in the AAPM CT performance phantom. CT slice images of the CT number calibration block were obtained with five scans each at 80, 100, 120, and 140 kVp X-ray beams. In the 5 CT slice images obtained for each tube voltage, the average CT number of the averages was calculated from the average CT numbers measured by setting the region of interest to water and 5 pins. For water and 5 pins, a linear regression analysis was performed on the average CT number of the averages calculated for each tube voltage versus the line attenuation coefficient for each photon energy, and the photon energies with the largest correlation coefficients of 58.5, 65, 71, and 77 keV were found to be effective photon energies. decided. The line attenuation coefficient used to determine this effective photon energy was automatically determined as the effective linear attenuation coefficient. For the effective photon energy, a linear equation was obtained by linear regression analysis of the average CT number of the averages in water and the five pins versus the difference in effective linear attenuation coefficient between the five pins and water. The contrast scale was determined by taking the slope of the obtained linear equation as the reciprocal. The determined contrast scale is 0.000198 to 0.000177 cm^-1 HU^-1 in the effective photon energy range of 58.5 to 77 keV. The contrast scale decreased as the effective photon energy increased.

• Progress in Medical Physics
• /
• v.19 no.3
• /
• pp.150-156
• /
• 2008

An applied technique of contrast enhancement for X-ray image is proposed which is based on combined enhancement of scaling and wavelet coefficients in discrete wavelet transform space. Conventional contrast enhancement methods such as contrast limited adaptive histogram equalization (CLAHE), multi-scale image contrast amplification (MUSICA) and gamma correction were applied on scaling coefficients to enhance the contrast of an original. In order to enhance the detail as well as reduce the blurring caused by up scaling of contrast modified scale coefficients from lower resolution, the sigmoid manipulation function was used to manipulate wavelet coefficients. The contrast detail mammography (CDMAM) phantom was imaged and processed to measure the image line profile of results and contrast to noise ratio (CNR) comparatively. The proposed technique produced better results than direct application of various contrast enhancement methods on image itself. The proposed method can enhance contrast, and also suppress the amplification of noise components in a single process. It could be useful for various applications in medical, industrial and graphical images where contrast and detail are of importance.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.2
• /
• pp.493-497
• /
• 2012

This study was conducted to retrospectively evaluate the pattern of contrast enhancement with SonoVue on gray-scale ultrasonography of hepatic angiomyolipoma (HAML). Imaging features of 33 pathologically proven HAML lesions in 33 patients who underwent baseline ultrasound and contrast-enhanced ultrasonography (CEUS) were assessed retrospectively. All lesions were enhanced in the arterial phase and showed whole-tumor filling in. Thirty-two of 33 (97%) lesions showed early positive enhancement in the arterial phase. Twenty-three of these exhibited isoechoic or hyperechoic features in the portal phase. HAML demonstrate characteristic manifestations with SonoVue-enhanced real-time gray-scale ultrasonography.

• Journal of Korea Multimedia Society
• /
• v.14 no.11
• /
• pp.1365-1372
• /
• 2011

This paper proposes a cognitive contrast enhancement algorithm based on the non-linear masking to advance low cognitive contrast in dark regions of images. In order to improve brightness in dark regions of an image, we propose a new contrast enhancement algorithm based on the non-linear masking using regional adaptive parameters of an image. For performance evaluation of the proposed method, chromaticity and saturation comparison as a quantitative assessment and z-score comparison as a qualitative assessment were executed between test images and their simulated images by SSR, MSR, a conventional non-linear masking and the proposed method, respectively. As a result, the proposed method showed low chromaticity and saturation difference and improved cognitive contrast for the three methods.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.4
• /
• pp.1846-1863
• /
• 2016

High dynamic range (HDR) images can present the perfect real scene and rich color information. A commonly encountered problem in practical applications is how to well visualize HDR images on standard display devices. In this paper, we propose a multi-scale decomposition method using guided filtering for HDR image tone mapping. In our algorithm, HDR images are directly decomposed into three layers：base layer, coarse scale detail layer and fine detail layer. We propose an effective function to compress the base layer and the coarse scale detail layer. An adaptive function is also proposed for detail adjustment. Experimental results show that the proposed algorithm effectively accomplishes dynamic range compression and maintains good global contrast as well as local contrast. It also presents more image details and keeps high color saturation.

• Korean Journal of Radiology
• /
• v.2 no.4
• /
• pp.197-203
• /
• 2001

Objective: To compare the clinical utility of contrast-enhanced color Doppler US in the differentiation of retinal detachment (RD) from vitreous membrane (VM) with that of various conventional US modalities, and to analyze the enhancement patterns in cases showing an enhancement effect. Materials and Methods: In 32 eyes examined over a recent two-year period, RD (n=14) and VM (n=18) were confirmed by surgery (n=28) or clinical follow-up (n=4). In all cases, gray-scale, color Doppler, and power Doppler US were performed prior to contrast injection, and after the intravenous injection of Levovist (Schering, Berlin) by hand for 30 seconds at a dose of 2.5 g and a concentration of 300 mg/mL via an antecubital vein, contrast-enhanced color Doppler US was performed. At Doppler US, the diagnostic criterion for RD and VM was whether or not color signals were visualized in membranous structures. Results: Diagnostic accuracy was 78% at gray-scale US, 81% at color Doppler US, 59% at power Doppler US, and 97% at contrast-enhanced color Doppler US. The sensitivity of color Doppler US to color signals in RD increased from 57% to 93% after contrast enhancement. The enhancement patterns observed were signal accentuation (n=3), signal extension (n=2), signal addition (n=3), and new signal visualization (n=5). Conclusion: Contrast-enhanced color Doppler US was the most accurate US modality for differentiating RD from VM, showing a significantly increased signal detection rate in RD.