BACKSUB

Name

backsub

Purpose

Background subtraction from an image.

Description

The background is determined from a robust fit of a line to each row
or column in the image depending on the keywords. If neither keyword
is set, then the robust mean is used. These lines or means are then
subtracted from the input image.
For each row (or column) that is fit, the 6 most extreme points (from
the mean) are removed from the first pass fit. See the docs for
GOODPOLY and the NEX keyword.

Calling Sequence

backsub,image, [ROW,COLUMN]

Inputs

image - Image (2-d or 3-d) to subtract background from, image is
modified in place.

Optional Input Parameters

Keyword Input Parameters

ROW - Flag, if set, program assumes that image is flat along a row.
COLUMN - Flag, if set, program assumes that image is flat along a column.
Default is to assume that the image is flat along rows and columns.
EXCLUDE- Scalar item or vector list of rows to exclude from background
fitting process.
KEEPMEAN - Flag, if set this program will NOT subtract the constant
term from the image if using a polynomical of order >= 1.
MAX_VALUE - The maximum value to be fitted. If this keyword is provided,
data values greater than MAX_VALUE are treated as missing
and are not used in the fit for the background.
MIN_VALUE - The minimum value to be fitted. If this keyword is provided,
data values greater than MIN_VALUE are treated as missing
and are not used in the fit for the background.
ORDER - Order of polynominal to fit to background (ROW and COLUMN only),
the default is 0 (mean of direction), 1 is linear, etc.
SILENT - If set, disables chatty output to screen.

Outputs

image - Background subtracted image.

Keyword Output Parameters

Common Blocks

Side Effects

Restrictions

Only one of ROW and COLUMN can be set.

Procedure

Modification History

93/11/12, Written by Marc W. Buie, Lowell Observatory
95/03/23, MWB, added ORDER keyword.
98/06/08, MWB, Added MIN/MAX_VALUE keywords.
2002/12/12, MWB, Added KEEPMEAN keyword.
2004/06/13, MWB, added support for UINT, ULONG, LONG64, ULONG64