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 computed by compositing the corresponding input pixels, with later input pictures over earlier ones. If the input images have no ALPHA 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 Digital Images,'' Computer Graphics, Vol 18, No. 3 (1984), pp. 253-259

BUGS

All pictures must have identical CHAN= attributes.