\
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.TH "Ppmcolormask User Manual" 1 "01 May 2006" "netpbm documentation"

.SH NAME
ppmcolormask - produce mask of areas of a certain color in a PPM file

.UN synopsis
.SH SYNOPSIS

\fBppmcolormask\fP \fB-color=\fP\fIcolor_list\fP [\fIppmfile\fP]
.PP
\fBppmcolormask\fP \fIcolor\fP [\fIppmfile\fP]

.UN examples
.SH EXAMPLES

.nf
\f(CW
    ppmcolormask -color red testimg.ppm >redmask.pbm
    pamcomp background.ppm testimg.ppm -alpha=redmask.pbm >test.ppm

    ppmcolormask -color=red,pink,salmon testimg.ppm >reddishmask.pbm

    ppmcolormask -color=bk:red,bk:orange,bk:yellow testimg.ppm >firemask.pbm

\fP

.fi

.UN description
.SH DESCRIPTION
.PP
This program is part of
.BR "Netpbm" (1)\c
\&.
.PP
\fBppmcolormask\fP reads a PPM file as input and produces a PBM
(bitmap) file as output.  The output file is the same dimensions as
the input file and is black in all places where the input file is a
color indicated by the \fB-color\fP option, and white everywhere
else.
.PP
The output of \fBppmcolormask\fP is useful as a transparency mask input
to \fBpamcomp\fP.  Note that you don't need \fBppmcolormask\fP and
\fBpamcomp\fP if you are ultimately converting to PNG with
\fBpnmtopng\fP because the \fB-transparent\fP option on \fBpnmtopng\fP does
the same thing.
.PP
\fIppmfile\fP is the input file.  If you don't specify
\fIppmfile\fP, the input is from Standard Input.
.PP
The output goes to Standard Output.
.PP
In the obsolete alternative syntax, specifying the \fIcolor\fP
names a single exact color to be masked.
.PP
\fBppmchange\fP does a similar thing: it modifies an image by
changing colors you specify to other colors you specify.  The two
programs give you somewhat different means of specifying colors in the
input image.
.PP
To make a mask of an image's background, without having to tell it
what color it is, use \fBpambackground\fP.

.UN options
.SH OPTIONS
.PP
In addition to the options common to all programs based on libnetpbm
(most notably \fB-quiet\fP, see 
.UR index.html#commonoptions
 Common Options
.UE
\&), \fBppmcolormask\fP recognizes the following
command line option:


.TP
\fB-color=\fP\fIcolor_list\fP
This mandatory option specifies the colors that are to be masked
(where the image is one of these colors, the output mask will be black).
.sp
Examples:


.IP \(bu
\fB-color=red\fP
.IP \(bu
\fB-color=red,pink,salmon\fP
.IP \(bu
\fB-color=rgb:80/80/ff\fP
.IP \(bu
\fB-color=bk:red,bk:orange,bk:yellow\fP

.sp
\fIcolor_list\fP is a list of colors separated by commas.  Each
color is either an exact color name as described for the 
.UR libnetpbm_image.html#colorname
argument of the \fBpnm_parsecolor()\fP library routine
.UE
\& or one of the 
.UR libppm.html#berlinkay
Berlin-Kay color names
.UE
\&.  In the
latter case, all colors that are better described by that Berlin-Kay
color name than any other are in the mask set.
.sp
The algorithm \fBppmcolormask\fP uses to determine to which colors
a Berlin-Kay color name applies is based on a Sugeno-type fuzzy
inference system developed by \fIKenan Kalajdzic\fP in 2006.  The
fuzzy model consists of partially linear membership functions defined
in the HSV color space.  Although more complex algorithms for fuzzy
color matching exist, this algorithm is intentionally simplified to
achieve a satisfactory speed using relatively compact code.
.sp
This option was new in Netpbm 10.34 (June 2006).  Before that,
you must use the \fIcolor\fP argument and cannot specify a Berlin-Kay
color.



.UN seealso
.SH SEE ALSO
.BR "pamfind" (1)\c
\&,
.BR "pambackground" (1)\c
\&,
.BR "ppmchange" (1)\c
\&,
.BR "pgmtoppm" (1)\c
\&,
.BR "pamcomp" (1)\c
\&,
.BR "pbmmask" (1)\c
\&,
.BR "pnmtopng" (1)\c
\&,
.BR "ppm" (1)\c
\&
.SH DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML
source.  The master documentation is at
.IP
.B http://netpbm.sourceforge.net/doc/ppmcolormask.html
.PP