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pnmhistmap(1) AMIGA (25 October 1993) pnmhistmap(1)
NAME
pnmhistmap - draw a histogram for a PGM or PPM file
SYNOPSIS
pnmhistmap [-black] [-white] [-max N] [-verbose] [pnmfile]
DESCRIPTION
Reads a portable anymap as input, although bitmap (PBM)
input produces an error message and no image. Produces an
image showing a histogram of the color (or gray) values in
the input. A graymap (PGM) input produces a bitmap output.
A pixmap (PPM) input produces pixmap output with three
overlaid histograms: a red one for the red input, a green
one for the green input, and a blue one for the blue input.
The output is fixed in size: 256 pixels wide by 200 pixels
high.
OPTIONS
-black
Ignores the count of black pixels when scaling the
histogram.
-white
Ignores the count of white pixels when scaling the
histogram.
The -black and -white options, which can be used seperately
or together, are useful for images with a large percentage
of pixels whose value is zero or 255, which can cause the
remaining histogram data to become unreadbaly small. Note
that, for pixmap inputs, these options apply to all colors;
if, for example, the input has a large number of bright-red
areas, you will probably want to use the -white option.
-max N
Force the scaling of the histogram to use N as the
largest-count value. This is useful for inputs with a
large percentage of single-color pixels which are not
black or white.
-verbose
Report the progress of making the histogram, including
the largest-count value used to scale the output.
All flags can be abbreviated to their shortest unique
prefix.
BUGS
Assumes maxval is always 255. Images with a smaller maxval
will only use the lower-value side of the histogram. This
can be overcome either by piping the input through "pnmdepth
255" or by cutting and scaling the lower-value side of the
Page 1 (printed 3/1/94)
pnmhistmap(1) AMIGA (25 October 1993) pnmhistmap(1)
histogram. Neither is a particularly elegant solution.
Should allow the output size to be specified.
SEE ALSO
pgmhist(1), ppmhist(1), pgm(5), ppm(5)
AUTHOR
Wilson H. Bent. Jr. (whb@usc.edu).
Page 2 (printed 3/1/94)