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Ppmbrighten User Manual(0)			    Ppmbrighten	User Manual(0)

       ppmbrighten - change a PPM image's Saturation and Value

       ppmbrighten	[-normalize]	 [-saturation=[+|-saturation_percent]]
       [-value=[+|-value_percent]] ppmfile

       Minimum unique abbreviation of option is	acceptable.  You may use  dou-
       ble  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.

       This program is part of Netpbm(1).

       ppmbrighten  increases  or decreases the	Saturation and Value (from the
       HSV color space)	of each	pixel of a PPM 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.

       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  PPM	format is also defined in terms	of a specified
       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 indi-
       cated by	the Hue	and Value.  A lower number means  more	light  of  the
       third primary color must	be added to get	the exact color.  Full Satura-
       tion 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%), ppmbrighten 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%),
       ppmbrighten 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 per cent-
       age, 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

       ppmflash	does another kind of brightening.  It  changes	the  color  of
       each  pixel  to bring it	a specified per	centage	closer to white.  This
       increases the value and saturation.

       pambrighten is the same as ppmbrighten, 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 transparency channel) get passed through.

       If you want to modify the Hues in the image, use	pamhue.

       To double the Value of each pixel:
       ppmbrighten -value=100

       To double the Saturation	and halve the Value of each pixel:
       ppmbrighten -saturation=+100 -value=-50

	      This option specifies the	amount,	as a per centage, by which you
	      want to change the Value of each pixel.  It may be negative.

	      This option specifies the	amount,	as a per centage, by which you
	      want  to	change	the Saturation of each pixel.  It may be nega-

	      This option causes ppmbrighten to	normalize contrast by linearly
	      remapping	the Values of the pixels to cover the range 0 to 1.

	      ppmbrighten  applies  the	 brightening that you specify with the
	      -value option after the remapping.

	      Before Netpbm 10.14 (March 2003),	your  input  must  be  from  a
	      seekable	file (not a pipe) to use -normalize.  If it isn't, the
	      program fails with a bogus error message.

       pnmnorm(1), ppmdim(1), pamfunc(1), ppmflash(1), pambrighten(1), pamalt-
       sat(1), pamdepth(1), pnmgamma(1), pamhue(1), ppmhist(1),	ppm(5)

       Copyright  (C)  1990  by	 Brian	Moffet.	  Copyright  (C)  1989	by Jef

       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 sup-
       porting documentation.  This software is	provided "as is"  without  ex-
       press or	implied	warranty.

       This  manual  page was generated	by the Netpbm tool 'makeman' from HTML
       source.	The master documentation is at

netpbm documentation		12 January 2019	    Ppmbrighten	User Manual(0)


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