XVista manual page

NAME

sub - to subtract image files

SYNOPSIS

sub file1 [file2] [const=] [box=] [outfile=]

DESCRIPTION

This routine computes the difference of the data in file1 and (if specified) file2. A constant offset can be specified optionally. The operation can take place in a specified box if a box has been specified previously. The computed difference is stored in file1.

The number of rows and columns in file1 must be equal to those in file2.

The subtracted image is put in file1 unless overridden by the outfile option.

EXAMPLE

sub alphalyr dark -subtracts the dark frame from the file `alphalyr'.

sub alphalyr const=45 - Subtracts 45 from each pixel in file `alphalyr'.

sub alphalyr const=2*sky box=1 - subtracts twice the variable SKY from file alflyr over the range specified in box number 1. It is assumed that the variable SKY was set by a prior SKY command.

SEE ALSO

add, mul, div,