• The Journal of the Korea Contents Association
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• v.15 no.11
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• pp.18-26
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• 2015

Geometric distortion and shadow effect due to capturing angle could be included in document copy images that are captured by a camera in stead of a scanner. In this paper, a clean black and white document image generation algorithm by distortion correction and shadow elimination based on a camera, is proposed. In order to correct geometric distortion such as straightening un-straight boundary lines occurred by camera lens radial distortion and eliminating outlying area included by camera direction, second derivative filter based document boundary detection method is developed. Black and white images have been generated by adaptive binarization method by eliminating shadow effect. Experimental results of the black and white document image generation algorithm by recovering geometrical distortion and eliminating shadow effect for the document images captured by smart phone camera, shows very good processing results.

• Journal of the Korea Society of Computer and Information
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• v.10 no.3 s.35
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• pp.143-150
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• 2005

Camera image is very sensitive to illumination that result in difficulties for recognizing character. Also Camera captured document images have not only skew but also vignetting effect and geometric distortion. Vignetting effect make it difficult to separate characters from the document images. Geometric distortion, occurred by the mismatch of angle and center position between the document image and the camera, make the shape of characters to be distorted, so that the character recognition is more difficult than the case of using scanner. In this paper, we propose a method that can increase the performance of character recognition by correcting the geometric distortion of document images using a linear approximation which changes the quadrilateral region to the rectangle one. The proposed method also determine the quadrilateral transform region automatically, using the alignment of character lines and the skewed angles of characters located in the edges of each character line. Proposed method, therefore, can correct the geometric distortion without getting positional information from camera.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.680-686
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• 2006

Document images captured by scanners have only skewing distortion. But camera captured document images have not only skew but also vignetting effect and geometric distortion. Vignetting effect, which makes the border areas to be darker than the center of the image, make it difficult to separate characters from the document images. But this effect has being decreased, as the lens manufacturing skill is developed. Geometric distortion, occurred by the mismatch of angle and center position between the document image and the camera, make the shape of characters to be distorted, so that the character recognition is more difficult than the case of using scanner. In this paper, we propose a method that can increase the performance of character recognition by correcting the geometric distortion of document images using a linear approximation which changes the quadrilateral region to the rectangle one. The proposed method also determine the quadrilateral transform region automatically, using the alignment of character lines and the skewed angles of characters located in the edges of each character line. Proposed method, therefore, can correct the geometric distortion without getting positional information from camera.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1541-1544
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• 2015

최근 스마트폰으로 워터마크가 인쇄된 문서를 촬영하여 유출을 하는 범죄가 일어나고 있으며, 특별한 감시 방안이 없다. 이를 위해 정부 및 기업에서는 문서의 외부 유출을 막기 위해 복사기 및 팩스 장치에 워터마크 패턴 보호 기법을 탑재하여 광학적으로 불법 복제를 방지한다. 특히 기업에 출입시 스마트폰에 보안 앱들을 설치하고, 스마트폰으로 문서를 촬영할 경우 앱이 보안 문서를 인식하여 경고를 시스템에 알린다. 그러나 스마트폰으로 촬영된 영상은 카메라의 위치와 각도에 따라 왜곡 현상이 발생되어 워터마크가 훼손된다. 이렇게 훼손된 영상은 기존 워터마크 패턴 인식 방법으로는 정상적으로 인식 되지 않는 문제가 있다. 본 논문에서는 실험을 통하여 훼손된 워터마크를 보정하고 인식하는 알고리즘을 이용하여 인식률과 처리속도를 높인다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.556-563
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• 2006

We should extract lines and data which consist of the table in order to classify the table region and analyze its structure in document image. But it is difficult to extract lines and data exactly because the lines are cut and their lengths are changed, or characters or noises are merged to the table lines. These problems result from the error of image input device or image reduction. In this paper, we propose the better method of extracting lines and data for table region classification and structure analysis than the previous ones including commercial softwares. The prposed method extracts horizontal and vertical lines which consist of the table by the use of one dimensional median filter. This filter not only eliminates the noises which attach to the line and the lines which are orthogonal to the filtering direction, but also connects the cut line of which the gap is shorter than the length of the filter tap in the process of extracting lines to the filtering direction. Furthermore, texts attached to the line are separated in the process of extracting vertical lines. This is an example of ABSTRACT format.