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- pgmnorm(1) Unix Programmer's Manual pgmnorm(1)
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- NNNAAAMMMEEE
- pgmnorm - normalize the contrast in a portable graymap
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- SSSYYYNNNOOOPPPSSSIIISSS
- pppgggmmmnnnooorrrmmm [-bbbpppeeerrrccceeennnttt _N | ---bbbvvvaaallluuueee _N] [-wwwpppeeerrrccceeennnttt _N | ---wwwvvvaaallluuueee _N] [_p_g_m_f_i_l_e]
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- DDDEEESSSCCCRRRIIIPPPTTTIIIOOONNN
- 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.
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- OOOPPPTTTIIIOOONNNSSS
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- 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 ---bbbpppeeerrrccceeennnttt and ---wwwpppeeerrrccceeennnttt flags, or you can
- specify the exact pixel values to be mapped by using the ---bbbvvvaaallluuueee and
- ---wwwvvvaaallluuueee 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.
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- All flags can be abbreviated to their shortest unique prefix.
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- SSSEEEEEE AAALLLSSSOOO
- pgmhist(1), pgm(5)
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- AAAUUUTTTHHHOOORRR
- Partially based on the fbnorm filter in Michael Mauldin's "Fuzzy Pixmap"
- package.
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- Copyright (C) 1989 by Jef Poskanzer.
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- 28 February 1989 1
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