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pgmnorm.1
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1995-07-25
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ppppggggmmmmnnnnoooorrrrmmmm((((1111)))) XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((22228888 FFFFeeeebbbbrrrruuuuaaaarrrryyyy 1111999988889999)))) ppppggggmmmmnnnnoooorrrrmmmm((((1111))))
NNNNAAAAMMMMEEEE
pgmnorm - normalize the contrast in a portable graymap
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
ppppggggmmmmnnnnoooorrrrmmmm [----bbbbppppeeeerrrrcccceeeennnntttt _N | ----bbbbvvvvaaaalllluuuueeee _N] [----wwwwppppeeeerrrrcccceeeennnntttt _N | ----wwwwvvvvaaaalllluuuueeee _N]
[_p_g_m_f_i_l_e]
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
Reads a portable graymap as input. Normalizes the contrast
by forcing the lightest pixels to white, the darkest pixels
to black, and linearly rescaling the ones in between; and
produces a portable graymap as output.
OOOOPPPPTTTTIIIIOOOONNNNSSSS
By default, the darkest 2 percent of all pixels are mapped
to black, and the lightest 1 percent are mapped to white.
You can override these percentages by using the ----bbbbppppeeeerrrrcccceeeennnntttt
and ----wwwwppppeeeerrrrcccceeeennnntttt flags, or you can specify the exact pixel
values to be mapped by using the ----bbbbvvvvaaaalllluuuueeee and ----wwwwvvvvaaaalllluuuueeee flags.
Appropriate numbers for the flags can be gotten from the
_p_g_m_h_i_s_t tool. If you just want to enhance the contrast,
then choose values at elbows in the histogram; e.g. if value
29 represents 3% of the image but value 30 represents 20%,
choose 30 for _b_v_a_l_u_e. If you want to lighten the image,
then set _b_v_a_l_u_e to 0 and just fiddle with _w_v_a_l_u_e; similarly,
to darken the image, set _w_v_a_l_u_e to maxval and play with
_b_v_a_l_u_e.
All flags can be abbreviated to their shortest unique
prefix.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
pgmhist(1), pgm(5)
AAAAUUUUTTTTHHHHOOOORRRR
Partially based on the fbnorm filter in Michael Mauldin's
"Fuzzy Pixmap" package.
Copyright (C) 1989 by Jef Poskanzer.
Page 1 (printed 9/7/93)