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     LERP(9.1)                                               LERP(9.1)

     NAME
          lerp, sub - linear combinations of images

     SYNOPSIS
          fb/lerp file fraction [ file fraction ... ]

          fb/sub file1 file2

     DESCRIPTION
          Lerp computes a linear combination of a number of input
          images.  Each input file name is followed by a floating-
          point fraction by which to scale its pixel values.  The
          fraction after the last image may be omitted, in which case
          one minus the sum of the other fractions is used.  The
          resulting image is written to standard output.

          Nothing prevents the fractions from being smaller than zero
          or larger than one.  Output pixel values that fall below
          zero or above 255 are clamped.

          Sub reads two images, which must be the same size and have
          the same number of channels.  Each channel of each pixel of
          the output image is the absolute value of the difference
          between the corresponding input values.

     SOURCE
          /sys/src/fb/lerp.c
          /sys/src/fb/sub.c

     SEE ALSO
          picfile(9.6)