.Dd January 19 2008 .Dt PNMCURVE 1 .Os .Sh NAME .Nm pnmcurve .Nd apply tone curves to pnm images .Sh SYNOPSIS .Nm .Op Fl r .Op Fl g .Op Fl b .Op Fl c Ar curve .Sh DESCRIPTION .Nm applies tone curves to pnm images. Curves are specified as a set of control points of a cubic spline. .Nm applies the resulting spline curve to the pnm image read from stdin and writes the resulting image to stdout. Command line switches allow to apply the curve only to selected color channels. .Pp The options are as follows: .Bl -tag -width indent .It Fl r Apply curve to red channel. .It Fl g Apply curve to green channel. .It Fl b Apply curve to blue channel. .It Fl c Curve to apply. Curves must be of the form x1:y1,x2:y2,x3:y3 where xi:yi are control points of a cubic spline curve. xi, yi must be in the range [0.0,1.0]. .El .Sh EXIT STATUS .Ex -std .Sh EXAMPLES .Dl "pnmcurve -c 0.0:0.0,0.5:0.2,1.0:1.0 < test.pnm > darker.pnm" .Pp .Sh SEE ALSO pnm(5) .Sh AUTHOR Johannes Hofmann