pgmhist(1) General Commands Manual pgmhist(1)NAME
pgmhist - print a histogram of the values in a portable graymap
SYNOPSIS
pgmhist [pgmfile]
DESCRIPTION
Reads a portable graymap as input. Prints a histogram of the gray values.
SEE ALSO pgmnorm(1), pgm(5), ppmhist(1)AUTHOR
Copyright (C) 1989 by Jef Poskanzer.
28 February 1989 pgmhist(1)
Check Out this Related Man Page
pgmnorm(1) General Commands Manual pgmnorm(1)NAME
pgmnorm - normalize the contrast in a portable graymap
SYNOPSIS
pgmnorm [-bpercent N | -bvalue N] [-wpercent N | -wvalue N] [pgmfile]
DESCRIPTION
Reads a portable graymap as input. Normalizes the contrast by forcing the lightest pixels to white, the darkest pixels to black, and lin-
early rescaling the ones in between; and produces a portable graymap as output.
OPTIONS
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 -bpercent and -wpercent flags, or you can specify the exact pixel values to be mapped by using the -bvalue
and -wvalue flags. Appropriate numbers for the flags can be gotten from the pgmhist 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 bvalue.
If you want to lighten the image, then set bvalue to 0 and just fiddle with wvalue; similarly, to darken the image, set wvalue to maxval
and play with bvalue.
All flags can be abbreviated to their shortest unique prefix.
SEE ALSO pgmhist(1), ppmnorm(1), pgm(5)AUTHOR
Partially based on the fbnorm filter in Michael Mauldin's "Fuzzy Pixmap" package.
Copyright (C) 1989 by Jef Poskanzer.
28 February 1989 pgmnorm(1)
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