NAME

       ppmmix - blend together two PPM images

SYNOPSIS

       ppmmix fadefactor ppmfile1 ppmfile2

DESCRIPTION

       This program is part of Netpbm(1).

       ppmmix  reads  two  PPM  images  as input and mixes them together using the specified fade
       factor.  The fade factor may be in the range from 0.0 (only ppmfile1's image data) to  1.0
       (only  ppmfile2's  image  data).  Anything in between specifies a smooth blend between the
       two images.

       The two images must have the same dimensions and the same  maxval.   Before  Netpbm  10.54
       (March 2011), they must also have the same type (PBM/PGM/PPM).

       The  fade  factor  is  applied to brightness, not light intensity.  That means for example
       that if you have a series of images you generated using ppmmix of  a  black  and  a  white
       image  with  a  linearly  increasing  fade  factor, you will see an image getting linearly
       brighter, but the light intensity will increase faster at the end.   That  is  because  it
       requires more intensity change at the bright end of the scale than at the dark end for the
       human eye to perceive the same brightness change.  This also means that  if  the  original
       images  aren't  all  one  color,  the  mixed  image  is  distorted,  since  the  intensity
       relationship between pixels is different from the original image.

       pamcomp is a more general alternative.  It allows you to mix images of different size  and
       to  have  the  fade  factor  vary  throughout the image (through the use of a transparency
       mask).  It does not have the same-maxval  and  same-type  restrictions.   It  mixes  light
       intensity, not brightness.

OPTIONS

       There  are  no command line options defined specifically for ppmmix, but it recognizes the
       options common to all programs based on libnetpbm (See
        Common Options ⟨index.html#commonoptions⟩ .)

SEE ALSO

       pamcomp(1), pammixmulti(1), ppm(1)

AUTHOR

       Copyright (C) 1993 by Frank Neumann

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/ppmmix.html