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Pamdepth User Manual(0)				       Pamdepth	User Manual(0)

       pamdepth	- change the depth (color resolution) in a Netpbm image

       pamdepth	newmaxval [netpbmfile]

       This program is part of Netpbm(1).

       pamdepth	 reads a Netpbm	image as input,	changes	its depth (color reso-
       lution),	and writes out the resulting Netpbm image.   I.e.  the	output
       has  a  different maxval	from the input,	but all	the same colors	(apart
       from rounding error).

       Reducing	the depth results in some loss of information.

       Here is an example of the effect	at the image format level: Assume  you
       start  with  an	image with maxval 100 and sample values	of 50 and 100.
       You tell	pamdepth to change it to depth 150.  The output	has maxval 200
       and sample values 75 and	150.

       This program works on multi-image streams.

       Be  careful of off-by-one errors	when choosing the new maxval.  For in-
       stance, if you want the color values to be five bits wide, use a	maxval
       of 31, not 32.

       One  important  use  of pamdepth	is to convert a	new format 2-byte-per-
       sample PNM file to the older 1-byte-per-sample  format.	 Before	 April
       2000,  essentially  all raw (binary) format PNM files had a maxval less
       than 256	and one	byte per sample, and many programs may rely  on	 that.
       If  you specify a newmaxval less	than 256, the resulting	file should be
       readable	by any program that worked with	PNM files before April 2000.

       pnm(5), pam(5), pnmquant(1), ppmdither(1) pambrighten(1)	pamfunc(1)

       pamdepth	was new	in Netpbm 10.32	 (February  2006).   It	 replaced  pn-
       mdepth,	by  Jef	 Poskanzer.   pamdepth is backward compatible with pn-
       mdepth and adds the ability to process arbitrary	 PAM  images  and  the
       ability	to  process  multi-image input streams.	 pnmdepth handled only
       PNM images and ignored all but the first	in any stream.

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

netpbm documentation	       19 December 2013	       Pamdepth	User Manual(0)


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