.TH LIGHT_CORRECT 1 "14 Oct 1996"
.SH NAME
light_correct \- correct illumination errors on set of images
.SH SYNOPSIS
.B light_correct grey image1 image2 image3 ...
.SH DESCRIPTION
The first argument should be an image of a piece of grey card, subsequent
arguments should be images taken with the same lighting set-up which need
correcting. The corrected images are written to files prefixed with "ic_". 

For example, suppose you have a directory with the following files in:

  example% ls
  dat1.1.v dat1.2.v dat2.1.v dat2.2.v dat3.1.v dat3.2.v
  dat4.1.v dat4.2.v grey.v

then run light_correct like this:

  example% light_correct grey.v dat*.v

to generate this:

  example% ls
  dat1.1.v dat1.2.v dat2.1.v dat2.2.v dat3.1.v dat3.2.v
  dat4.1.v dat4.2.v grey.v
  ic_dat1.1.v ic_dat1.2.v ic_dat2.1.v ic_dat2.2.v ic_dat3.1.v
  ic_dat3.2.v ic_dat4.1.v ic_dat4.2.v

light_correct works by smoothing out the grey card image, finding
grey-mean/pixel for each point, and then multiplying the result by all the
following images. It also removes any .desc files it generates, to avoid
problems with im_global_balance(3).

.SH RETURN VALUE
returns 0 on success and non-zero on error.
.SH SEE ALSO
header(1), vips(1)
.SH COPYRIGHT
The National Gallery and Birkbeck College, 1989-1996.