• Title/Summary/Keyword: Image Edge

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Estimation of Chlorophyll-a Concentrations in the Nakdong River Using High-Resolution Satellite Image (고해상도 위성영상을 이용한 낙동강 유역의 클로로필-a 농도 추정)

  • Choe, Eun-Young;Lee, Jae-Woon;Lee, Jae-Kwan
    • Korean Journal of Remote Sensing
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    • v.27 no.5
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    • pp.613-623
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    • 2011
  • This study assessed the feasibility to apply Two-band and Three-band reflectance models for chlorophyll-a estimation in turbid productive waters whose scale is smaller and narrower than ocean using a high spatial resolution image. Those band ratio models were successfully applied to analyzing chlorophyll-a concentrations of ocean or coastal water using Moderate Imaging Spectroradiometer(MODIS), Sea-viewing Wide Field-fo-view Sensor(SeaWiFS), Medium Resolution Imaging Spectrometer(MERIS), etc. Two-band and Three-band models based on band ratio such as Red and NIR band were generally used for the Chl-a in turbid waters. Two-band modes using Red and NIR bands of RapidEye image showed no significant results with $R^2$ 0.38. To enhance a band ratio between absorption and reflection peak, We used red-edge band(710 nm) of RapidEye image for Twoband and Three-band models. Red-RE Two-band and Red-RE-NIR Three-band reflectance model (with cubic equation) for the RapidEye image provided significance performances with $R^2$ 0.66 and 0.73, respectively. Their performance showed the 'Approximate Prediction' with RPD, 1.39 and 1.29 and RMSE, 24.8, 22.4, respectively. Another three-band model with quadratic equation showed similar performances to Red-RE two-band model. The findings in this study demonstrated that Two-band and Three-band reflectance models using a red-edge band can approximately estimate chlorophyll-a concentrations in a turbid river water using high-resolution satellite image. In the distribution map of estimated Chl-a concentrations, three-band model with cubic equation showed lower values than twoband model. In the further works, quantification and correction of spectral interferences caused by suspended sediments and colored dissolved organic matters will improve the accuracy of chlorophyll-a estimation in turbid waters.

Image Segmentation Using Morphological Operation and Region Merging (형태학적 연산과 영역 융합을 이용한 영상 분할)

  • 강의성;이태형;고성제
    • Journal of Broadcast Engineering
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    • v.2 no.2
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    • pp.156-169
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    • 1997
  • This paper proposes an image segmentation technique using watershed algorithm followed by region merging method. A gradient image is obtained by applying multiscale gradient algorithm to the image simplified by morphological filters. Since the watershed algorithm produces the oversegmented image. it is necessary to merge small segmented regions as wel]' as region having similar characteristics. For region merging. we utilize the merging criteria based on both the mean value of the pixels of each region and the edge intensities between regions obtained by the contour following process. Experimental results show that the proposed method produces meaningful image segmentation results.

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Recent Developments in Imaging Systems and Processings-3 Dimensional Computerized Tomography (영상 System의 처리의 근황-전산화 3차원 단층 영상처리)

  • 조장희
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.15 no.6
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    • pp.8-22
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    • 1978
  • Recently developed Computed Topography (CT) reconstruction algorithms are reviewed in a more generalized sense and a few reconstruction examples are given for illustration. The construction of an image function from the physically measured projections of some object is Discussed with reference to the least squares optimum filters, originally derived to enhance the signal-to-noise ratio in communications theory. The computerifed image processing associated with topography is generalized so as to include 3 distinct parts: the construction of an image from the projection, the restoration of a blurred, noisy image, degraded by a known space-invariant impulse response, and the further enhancement of the image, e.g. by edge sharpening. In conjunction with given versions of the popular convolution algorithm, n6t 19 be confused with filtering by a 2-diminsional convolution, we consider the conditions under which a concurrent construction, restoration, and enhancement are possible. Extensive bibliographical limits are given in the references.

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A Level Set Method to Image Segmentation Based on Local Direction Gradient

  • Peng, Yanjun;Ma, Yingran
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.4
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    • pp.1760-1778
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    • 2018
  • For image segmentation with intensity inhomogeneity, many region-based level set methods have been proposed. Some of them however can't get the relatively ideal segmentation results under the severe intensity inhomogeneity and weak edges, and without use of the image gradient information. To improve that, we propose a new level set method combined with local direction gradient in this paper. Firstly, based on two assumptions on intensity inhomogeneity to images, the relationships between segmentation objects and image gradients to local minimum and maximum around a pixel are presented, from which a new pixel classification method based on weight of Euclidian distance is introduced. Secondly, to implement the model, variational level set method combined with image spatial neighborhood information is used, which enhances the anti-noise capacity of the proposed gradient information based model. Thirdly, a new diffusion process with an edge indicator function is incorporated into the level set function to classify the pixels in homogeneous regions of the same segmentation object, and also to make the proposed method more insensitive to initial contours and stable numerical implementation. To verify our proposed method, different testing images including synthetic images, magnetic resonance imaging (MRI) and real-world images are introduced. The image segmentation results demonstrate that our method can deal with the relatively severe intensity inhomogeneity and obtain the comparatively ideal segmentation results efficiently.

Suitability of the PKNU 2 System for Generating the Orthophoto Map

  • Lee, Eun-Khung;Lee, Chang-Hun;Choi, Chul-Uong;Kim, Young-Seup
    • Proceedings of the KSRS Conference
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    • 2003.11a
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    • pp.100-102
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    • 2003
  • This system is capable of obtaining quantitative information from images using natural features on the ortho-image maps that correspond with those from topographical maps. However, the qualitative information can also be obtained because because of the excellent visibility of ortho-image maps. There are plenty of promise for the use of ortho-image maps in the next generation topographic technology because of its wider applicability within the field. In keeping with the cutting edge, we produced ortho-image maps by scanning a specified area in narrow sections using the PKNU 2: a multispectral digital aerial photographing system made by ourselves. We evaluated the precision of the ortho-image maps, and performed an evaluation of the PKNU 2 system's capacity to improve the equipment of the PKNU 2. Ortho-image maps were made using Ground Control Points (GCPs) which were obtained from digital maps and aerial photographs of the PKNU 2. Thus, we demonstrated that it was possible to produce the ortho-image maps, which has a good constant level rate of less than 1m. The PKNU 2 system needs to be improving in the sensitivity of level maintenance equipment in the evaluation in terms of performance. It is thus required to survey the GCPs precisely for an accurate study.

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New Medical Image Fusion Approach with Coding Based on SCD in Wireless Sensor Network

  • Zhang, De-gan;Wang, Xiang;Song, Xiao-dong
    • Journal of Electrical Engineering and Technology
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    • v.10 no.6
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    • pp.2384-2392
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    • 2015
  • The technical development and practical applications of big-data for health is one hot topic under the banner of big-data. Big-data medical image fusion is one of key problems. A new fusion approach with coding based on Spherical Coordinate Domain (SCD) in Wireless Sensor Network (WSN) for big-data medical image is proposed in this paper. In this approach, the three high-frequency coefficients in wavelet domain of medical image are pre-processed. This pre-processing strategy can reduce the redundant ratio of big-data medical image. Firstly, the high-frequency coefficients are transformed to the spherical coordinate domain to reduce the correlation in the same scale. Then, a multi-scale model product (MSMP) is used to control the shrinkage function so as to make the small wavelet coefficients and some noise removed. The high-frequency parts in spherical coordinate domain are coded by improved SPIHT algorithm. Finally, based on the multi-scale edge of medical image, it can be fused and reconstructed. Experimental results indicate the novel approach is effective and very useful for transmission of big-data medical image(especially, in the wireless environment).

Medical Image Enhancement Using an Adaptive Weight and Threshold Values (적응적 가중치와 문턱치를 이용한 의료영상의 화질 향상)

  • Kim, Seung-Jong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.12 no.5
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    • pp.205-211
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    • 2012
  • By using an adaptive threshold and weight based on the wavelet transform and Haar transform, a novel image enhancement algorithm is proposed. First, a medical image was decomposed with wavelet transform and all high-frequency sub-images were decomposed with Haar transform. Secondly, noise in the frequency domain was reduced by the proposed soft-threshold method. Thirdly, high-frequency coefficients were enhanced by the proposed weight values in different sub-images. Then, the enhanced image was obtained through the inverse Haar transform and wavelet transform. But the pixel range of the enhanced image is narrower than a normal image. Lastly, the image's histogram was stretched by nonlinear histogram equalization. Experiments showed that the proposed method can be not only enhance an image's details but can also preserve its edge features effectively.

A Pen Drawing Method by Tensor-based Strokes Generation (텐서 기반 스트로크 생성에 의한 펜화기법)

  • Shin, Do-kyung;Ahn, Eun-young
    • Journal of Korea Multimedia Society
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    • v.20 no.4
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    • pp.713-720
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    • 2017
  • We present a non-photo realistic pen-ink drawing method for outlining and shading of the input image. Especially, we focus on the detailed illustration of the image of which stroke's direction is important. The pen-ink renderer is an alternative display models user can generate traditional illustration renderings of their photo realistic image. The previously proposed pen drawing methods produce feasible description in general image but it is difficult to express in detail for the sophisticated images that need to consider the direction of stroke for each image region. In order to overcome the disadvantages of the conventional method, a direction vector is extracted from a tensor field and we determine a stroke's direction in consideration of not only an edge area but also a gradient of a surrounding area in the image. For more detailed description for the sophisticated image, we generate white noises based on the light and shade of the input image and determine the direction and length of the stroke by using the tensor field for each generated white noise. The proposed method works particularly well for traditional architectural images where the direction and detailed description of the pen is important.

Deskewing Document Image using the Gradient of the Spaces Between Sentences. (문장 사이의 공백 기울기를 이용한 문서 이미지 기울기 보정)

  • Heo, Woo-hyung;Gu, Eun-jin;Kim, Cheol-ki;Cha, Eui-young
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2013.05a
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    • pp.379-381
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    • 2013
  • In this paper, we propose a method to detect the gradient of the spaces between sentences and to deskew in the document image. First, gradient is measured by pixels for spaces between sentences that has been done an edge extraction in document image and then skewed image is corrected by using the value of the gradient which has been measured. Since document image is divided into several areas, it shows a robust processing result by handling the margin, images, and multistage form in the document. Because the proposed method does not use pixel of the character region but use the blank area, degraded document image as well as vivid document image is effectively corrected than conventional method.

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Image Deblocking Scheme for JPEG Compressed Images Using an Adaptive-Weighted Bilateral Filter

  • Wang, Liping;Wang, Chengyou;Huang, Wei;Zhou, Xiao
    • Journal of Information Processing Systems
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    • v.12 no.4
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    • pp.631-643
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    • 2016
  • Due to the block-based discrete cosine transform (BDCT), JPEG compressed images usually exhibit blocking artifacts. When the bit rates are very low, blocking artifacts will seriously affect the image's visual quality. A bilateral filter has the features for edge-preserving when it smooths images, so we propose an adaptive-weighted bilateral filter based on the features. In this paper, an image-deblocking scheme using this kind of adaptive-weighted bilateral filter is proposed to remove and reduce blocking artifacts. Two parameters of the proposed adaptive-weighted bilateral filter are adaptive-weighted so that it can avoid over-blurring unsmooth regions while eliminating blocking artifacts in smooth regions. This is achieved in two aspects: by using local entropy to control the level of filtering of each single pixel point within the image, and by using an improved blind image quality assessment (BIQA) to control the strength of filtering different images whose blocking artifacts are different. It is proved by our experimental results that our proposed image-deblocking scheme provides good performance on eliminating blocking artifacts and can avoid the over-blurring of unsmooth regions.