LAM(9.1)                                                 LAM(9.1)

     NAME
          lam, posit, piccat, picjoin - combine several images

     SYNOPSIS
          fb/lam input ...

          fb/posit input ...

          fb/piccat input ...

          fb/picjoin input ...

     DESCRIPTION
          Lam overlays (laminates) several picture files, writing the
          resulting picture file to standard output.  The output
          WINDOW= attribute is the smallest rectangle that contains
          all of the input rectangles.  Each pixel of the output image
          takes its value from the last-mentioned input image that
          covers that pixel.  Output pixels not covered by any input
          image are set to zero.

          Posit performs similarly, except that output pixels are com-
          puted by compositing the corresponding input pixels, with
          later input pictures over earlier ones.  If the input images
          have no α channel, posit has the same effect as lam.

          Piccat concatenates a list of picture files, each above the
          next, writing the result to standard output.  The width of
          the output file will be that of the widest input picture.
          If any of the input pictures are more narrow than that, the
          space to their right will be zero in the output picture.

          Picjoin is similar, but joins the pictures left-to right.

     SOURCE
          /sys/src/fb/lam.c
          /sys/src/fb/posit.c
          /sys/src/fb/piccat.c
          /sys/src/fb/picjoin.c

     SEE ALSO
          picfile(9.6), Thomas Porter and Tom Duff, ``Compositing Dig-
          ital Images,'' Computer Graphics, Vol 18, No. 3 (1984), pp.
          253-259

     BUGS
          All pictures must have identical CHAN= attributes.