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PNMCONVO.MAN
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1991-08-11
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pnmconvol(1) Unix Programmer's Manual pnmconvol(1)
NNNAAAMMMEEE
pnmconvol - general MxN convolution on a portable anymap
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pppnnnmmmcccooonnnvvvooolll _c_o_n_v_o_l_u_t_i_o_n_f_i_l_e [_p_n_m_f_i_l_e]
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Reads two portable anymaps as input. Convolves the second using the
first, and writes a portable anymap as output.
Convolution means replacing each pixel with a weighted average of the
nearby pixels. The weights and the area to average are determined by the
convolution matrix. The unsigned numbers in the convolution file are
offset by -maxval/2 to make signed numbers, and then normalized, so the
actual values in the convolution file are only relative.
Here is a sample convolution file; it does a simple average of the
immediate neighbors, resulting in a smoothed image:
P2
3 3
18
10 10 10
10 10 10
10 10 10
The convolution file will usually be a bitmap or graymap instead of a
pixmap, so that the same convolution gets applied to each color
component. However, if you want to use a pixmap and do a different
convolution to different colors, you can certainly do that.
SSSEEEEEE AAALLLSSSOOO
pnm(5)
AAAUUUTTTHHHOOORRR
Copyright (C) 1989, 1991 by Jef Poskanzer.
13 January 1991 1