Yujin Yun

Bio: Yujin Yun is an academic researcher from Yonsei University. The author has contributed to research in topics: Interpolation & Stairstep interpolation. The author has an hindex of 4, co-authored 6 publications receiving 33 citations.

Multidirectional edge-directed interpolation with region division for natural images

Abstract: Yujin Yun, Jonghyun Bae, and Jaeseok KimYonsei University, Department of Electrical and ElectronicEngineering, 50 Yonsei-ro, Seodaemun-gu, Seoul,Republic of KoreaE-mail: yujin.yun@yonsei.ac.krAbstract. A multidirectional edge-directed interpolation algo-rithm that features a region division method is proposed. Inthe proposed method, an interpolation pixel is newly modeledas a weighted sum of 12 neighboring pixels representing 12different directions. Each weight is estimated by Wiener filtertheory using geometric duality. The proposed method fordividing the interpolation region reduces the heavy computa-tional complexity of the proposed model. Analyzing edgecontinuities, the model divides an image into three regions,and only strong edge regions are interpolated. Simulationresults show that several directional edges are restoredclearly in a subjective test, with fair performance in an objec-tive test.

Adaptive multidirectional edge directed interpolation for selected edge regions

Abstract: This paper proposes an adaptive edge-directed interpolation algorithm using multidirectional neighbor pixels. In order to restore multidirectional edges, a missing pixel is estimated as a weighted sum of 12 neighbor pixels. Based on the geometric duality between a low resolution image and a high resolution image, interpolation coefficients are predicted using Wiener filter theory. In order to reduce the computational complexity, interpolation region selection method is also proposed. An edge map for a low resolution image is obtained by canny edge detector. By analyzing edge continuities, only long edge regions are interpolated using 12 neighbor pixels. Short edge regions are interpolated by new edge-directed interpolation, and even regions are interpolated by a linear interpolation. Simulation results show that a proposed method restores major edges with several directions better than other methods in subjective tests while showing fair performance in objective tests.

A new edge directed interpolation algorithm using accurate estimation of edge directional covariance

Abstract: This paper proposes an edge-directed interpolation algorithm to enhance the quality of natural images which are captured by low-resolution camera installed on car or CCTV. Based on the accurate estimation of edge directional covariance between low-resolution and high-resolution image, local covariance coefficients extracted from the low-resolution image has been adapted for the interpolation to obtain the high-resolution image. DCT (Discrete Cosine Transform) kernel function is used in order to reflect the multi-directional edge accurately without increasing of complexity. Simulation result shows that our new interpolation algorithm significantly improves the subjective quality of the interpolated images compared with conventional linear interpolation and NEDI one. It also demonstrates the improvements of objective metrics such as PSNR, SSIM(structural similarity index measurement) and WEA (Wiener filter coefficients Estimation Accuracy) which are used for the accuracy estimation of directionality.

Adaptive tone-mapping operator for HDR images based on image statistics

Abstract: In this paper, we present a novel segmentation method for displaying high dynamic range image based on K-means clustering. The new segmentation method uses statistical features of an image in a logarithmic luminance domain. Each divided region is applied to different global tone mapping operators respectively. The global tone mapping operator is a logarithmic tone mapping with a different user parameters. The parameters for applying to each region are calculated using a centroid which is obtained from K-means clustering. According to results of many HDR image experiments, we demonstrate that our method is faster than other local tone mapping operators and improves an image rendering performance in terms of dark area details and contrast enhancement.

Apparatus and method for interpolating image, and apparatus for processing image using the same

Abstract: An image interpolation apparatus is provided which includes an edge area distinguishing part configured to distinguish an edge area including an edge from an image; an edge area classifying part configured to classify the edge area into a plurality of regions; and an interpolation part configured to perform interpolation the regions in different manners.

Multidirectional Weighted Interpolation and Refinement Method for Bayer Pattern CFA Demosaicking

Abstract: This paper presents a novel multidirectional weighted interpolation algorithm for color filter array interpolation. Our proposed method has two contributions to demosaicking. First, different from conventional interpolation methods based on two directions or four directions, the proposed method exploits to greater degree correlations among neighboring pixels along eight directions to improve the interpolation performance. Second, we propose an efficient postprocessing method to reduce interpolation artifacts based on the color difference planes. Compared with conventional state-of-the-art demosaicking algorithms, our experimental results show the proposed algorithm provides superior performance in both objective and subjective image quality. Furthermore, this implementation has moderate computational complexity.

Multidirectional Weighted Interpolation and Refinement Method for Bayer Pattern

Abstract: This paper presents a novel multidirectional weighted interpolation algorithm for color filter array inter- polation. Our proposed method has two contributions to demosaicking. First, different from conventional interpolation methods based on two directions or four directions, the proposed method exploits to greater degree correlations among neighboring pixels along eight directions to improve the interpolation perfor- mance. Second, we propose an efficient postprocessing method to reduce interpolation artifacts based on the color difference planes. Compared with conventional state-of-the-art demosaick- ing algorithms, our experimental results show the proposed algorithm provides superior performance in both objective and subjective image quality. Furthermore, this implementation has moderate computational complexity.

Bayer Pattern CFA Demosaicking Based on Multi-Directional Weighted Interpolation and Guided Filter

Abstract: In this letter, we proposed a new framework for color image demosaicking by using different strategies on green (G) and red/blue (R/B) components. Firstly, for G component, the missing samples are estimated by eight-direction weighted interpolation via exploiting spatial and spectral correlations of neighboring pixels. The G plane can be well reconstructed by considering the joint contribution of pre-estimations along eight interpolation directions with different weighting factors. Secondly, we estimate R/B components using guided filter with the reconstructed G plane as guidance image. Simulation results verify that, the proposed framework performs better than state-of-the-art demosaicking methods in term of color peak signal-to-noise ratio (CPSNR) and feature similarity index measure (FSIM), as well as higher visual quality.

Encoding perceptually-quantized video content in multi-layer vdr coding

Abstract: Input VDR images are received. A candidate set of function parameter values for a mapping function is selected from multiple candidate sets. A set of image blocks of non-zero standard deviations in VDR code words in at least one input VDR image is constructed. Mapped code values are generated by applying the mapping function with the candidate set of function parameter values to VDR code words in the set of image blocks in the at least one input VDR image. Based on the mapped code values, a subset of image blocks of standard deviations below a threshold value in mapped code words is determined as a subset of the set of image blocks. Based at least in part on the subset of image blocks, it is determined whether the candidate set of function parameter values is optimal for the mapping function to map the at least one input VDR image.

Methods and apparatus to capture photographs using mobile devices

Abstract: Methods and apparatus to capture photographs using mobile devices are disclosed. An example method includes receiving sensor data from a sensor in a mobile device. The example method further includes presenting visual feedback to a user, via a display of the mobile device, to guide the user in capturing a photograph with a camera of the mobile device. The visual feedback based on the sensor data.