Pambrighten User Manual(1) General Commands Manual Pambrighten User Manual(1)
NAME
pambrighten - change a PPM image's Saturation and Value
SYNOPSIS
pambrighten [-saturation=[+|-]saturation_percent]
[-value=[+|-]value_percent] [netpbmfile]
Minimum unique abbreviation of option is acceptable. You may use double
hyphens instead of single hyphen to denote options. You may use white
space in place of the equals sign to separate an option name from its
value.
DESCRIPTION
This program is part of Netpbm(1).
pambrighten increases or decreases the Saturation and Value (from the
HSV color space) of each pixel of a Netpbm image. You specify the per-
centage change for each of those parameters.
You can also remap the colors of the pixels so their Values cover the
full range of possible Values.
The input image is from the file named netpbmfile, or Standard Input if
netpbmfile is not specified.
The output format is the same as the input format and any extra chan-
nels, such as transparency, are passed through.
Hue-Saturation-Value, or HSV, is one way to represent a color, like the
more well-known RGB. Hue, Saturation, and Value are numbers in the
range from 0 to 1. We always capitalize them in this document when we
mean the number from the HSV color space, especially since "value" as a
conventional English word has a much more abstract meaning.
Value is a measure of how bright the color is, relative to some speci-
fied maximum (the Netpbm formats are also defined in terms of a speci-
fied maximum brightness -- For the purposes of this program, they are
the same). In particular, it is the brightness of the brightest primary
color component of the color divided by the maximum brightness possible
for a component. Zero Value means black. White has full Value.
Hue is an indication of the secondary color with the same brightness
that most closely approximates the color. A secondary color is made of
a combination of at most two of the primary colors.
Saturation is a measure of how close the color is to the color indicated
by the Hue and Value. A lower number means more light of the third pri-
mary color must be added to get the exact color. Full Saturation means
the color is a secondary color. Zero Saturation means the color is gray
(or black or white). Decreasing the saturation of a color tends to make
it washed out.
If it is impossible to increase the Value of a pixel by the amount you
specify (e.g. the Value is .5 and you specify +200%), pambrighten in-
creases it to full Value instead.
If it is impossible to increase the Saturation of a pixel by the amount
you specify (e.g. it is already half saturated and you specify +200%),
pambrighten increases it to full Saturation instead.
For a simpler kind of brightening, you can use pamfunc -multiplier sim-
ply to increase the brightness of each pixel by a specified percentage,
clipping each RGB component where the calculated brightness would exceed
full brightness. Thus, the brightest colors in the image would change
chromaticity in addition to not getting the specified brightness boost.
For decreasing brightness, pamfunc should do the same thing as pam-
brighten.
ppmflash does another kind of brightening. It changes the color of each
pixel to bring it a specified percentage closer to white. This in-
creases the value and saturation.
pambrighten is meant to replace ppmbrighten. It is the same as ppm-
brighten, except that it recognizes the various Netpbm image formats
rather than treating them all as PPM. The output format is the same as
the input format and extra channels in a PAM image (such as a trans-
parency channel) get passed through.
If you want to modify the hues in the image, use pamhue.
EXAMPLES
To double the Value of each pixel:
pambrighten -value=100
To double the Saturation and halve the Value of each pixel:
pambrighten -saturation=+100 -value=-50
OPTIONS
In addition to the options common to all programs based on libnetpbm
(most notably -quiet, see ]8;;index.html#commonoptions\ Common Options]8;;\ ), pambrighten recognizes the
following command line options:
-value=value_percent
This option specifies the amount, as a percentage, by which you
want to increase the Value of each pixel. It may be negative.
The default is zero.
-saturation=value_percent
This option specifies the amount, as a percentage, by which you
want to increase the Saturation of each pixel. It may be nega-
tive.
The default is zero.
SEE ALSO
pnmnorm(1), ppmdim(1), pamfunc(1), ppmflash(1), pamaltsat(1),
pamdepth(1), pnmgamma(1), pamhue(1), ppmhist(1), ppm(1)
HISTORY
pambrighten was new in Netphm 10.86 (March 2019). It was a PAM conver-
sion of the much older ppmbrighten.
AUTHOR
Copyright (C) 1990 by Brian Moffet. Copyright (C) 1989 by Jef
Poskanzer.
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, pro-
vided that the above copyright notice appear in all copies and that both
that copyright notice and this permission notice appear in supporting
documentation. This software is provided "as is" without express or im-
plied warranty.
DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML
source. The master documentation is at
http://netpbm.sourceforge.net/doc/pambrighten.html
netpbm documentation 18 August 2020 Pambrighten User Manual(1)
Generated by dwww version 1.16 on Tue Dec 16 05:03:24 CET 2025.