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lpsmooth(1) General Commands Manual lpsmooth(1) NAME lpsmooth - smooth an image preserving thin lines (v1.2) SYNOPSIS lpsmooth [-options] in_file | - out_file | - DESCRIPTION lpsmooth reads a portable graymap(5) or a portable pixmap(5) as input, smooth the image slightly preserving thin lines, and produces a portable graymap/pixmap as output. If -p 3 (default), lpsmooth smooths the image along thin lines, whose thickness is 1 pixel, ensuring that no line is blurred in the direction or- thogonal to the line locally. A 3x3 mask is put on every pixel in the image. lpsmooth finds the pixels whose color (or graylevel) is 1st through (N-1)th similar to that of the central pixel, where N is given by the option "-p N." The color of the cen- tral pixel is turned into the average color of the N pixels including the central pixel. Color difference is measured by the Euclidean distance in the RGB color space. If the string "-" is passed instead of in_file, lpsmooth reads the image from standard input. If the string "-" is passed instead of out_file, lpsmooth writes the image to standard output. OPTIONS -n N Specifies how many times (N) the smoothing operation is applied to the image. The default value is N=1. -w N The weight factor for the central pixel in each 3x3 mask. The de- fault value is N=1. If -p N and -w 0, the processing is identical to the k-nearest neighbor smoothing with k=N-1. See references for the details of the method. -p N Specifies the number of the using pixels including the central pixel. The default value is N=3, i.e., 2 pixels nearest in color (graylevel) affect the new color of the central pixel. If the input image is noisy, -p 4 or -p 5 will be helpful. If -p 9 and -w 1, the processing is identical to calculating the moving average with a 3x3 mask. If -p 1, lpsmooth does nothing ex- cept consuming some memory and enormous CPU power. -verbose Show processing information. NOTES Even if -p 3, line segments may get shorter by at most 2 pixels, because the two pixels on the edges of a line segment are blurred slightly. For the color image processing, the color similarity is measured by the Eu- clidian distance in RGB color space. SEE ALSO pgm(5), ppm(5) REFERENCES L.S. Davis and A. Rosenfeld, "Noise Cleaning by Iterated Local Averaging," IEEE Trans. SMC, vol.SMC-8, No.9, pp.705-710, 1978. AUTHOR Copyright (C) 2000-2002 Hideaki Goto E-Mail: hgot@rd.isc.tohoku.ac.jp, hgot@aso.ecei.tohoku.ac.jp Feb 2002 lpsmooth(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | SEE ALSO | REFERENCES | AUTHOR
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