Image analysis – Image enhancement or restoration – Edge or contour enhancement
Patent
1998-07-15
2000-03-21
Lee, Thomas D.
Image analysis
Image enhancement or restoration
Edge or contour enhancement
382262, 382233, G06K 940, G06K 936
Patent
active
060411457
ABSTRACT:
A great decrease of a step, i.e., block distortion, of such as unnatural, abnormal or artifact brightness and color, on a block boundary, leads to much visual improvement of picture quality. Against a picture that has been encoded and decoded by block, the smoothing filter characteristics is changed according to quantizing parameter, block activity of a decoded picture, the activity of each pixel of the decoded picture, and the position with respect to a block boundary of a pixel. A smoothing filter utilizes a weighted mean whose weight is the inverse number of a difference between a target pixel and its surrounding pixels. The weighted mean is obtained by adding a certain number to a weight before taking its inverse number. The value to be added is controlled by the parameter. Similarly, the mixing ratio of a pixel value after performing the smoothing filter and a decoded pixel value is changed depending on the parameter. A filter having strong edge preserving property is utilized for the inside of a block, and a filter having weak edge preserving property is utilized for a block boundary. A filter having edge preserving property is utilized for the post/loop filter.
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patent: 5610729 (1997-03-01), Nakajima
Computer Graphics & Image Processing 15, pp. 167-181 (1981), "Gradient Inverse Weighted Smoothing Scheme & The Evaluation of Its Performance" by Wang et al.
Technical Report of IEICE, IE94-7 DSP94-7 (1994-04), "Postprocessing Algorithms for Noise Reduction of MPEG Coded Video" by Nakajima.
Technical Report of IEICE84-46, "Study of the Method for Improving the Image Quality of Block Encoding Picture by Post Filter Process" by Mitsuya et al.
"Motion Video Coding for Visual Telephony"; Ronald Plompen; 1990, PTT Research Neher Labs, NL, Leidschendam XP002096009 198180 *p. 179-p. 208*.
"On the Gradient Inverse Weighted Filter"; Wang Xin; IEEE Transactions on Signal Processing, vol. 40, No. 2; Feb. 1, 1992, pp. 482-484, XP000292345 *the whole document*.
Etoh Minoru
Hayashi Takaaki
Chen Wenpeng
Lee Thomas D.
Matsushita Electric - Industrial Co., Ltd.
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