AIPS HELP file for IMFLT in 31DEC22
As of Tue Oct 3 7:02:46 2023
IMFLT: Flattens an image by fitting a plane to the image.
INNAME Input image name (name)
INCLASS Input image name (class)
INSEQ 0.0 9999.0 Input image name (seq. #)
INDISK 0.0 9.0 Input image disk unit #
OUTNAME Output image name (name)
OUTCLASS Output image name (class)
OUTSEQ -1.0 9999.0 Output image name (seq. #)
OUTDISK 0.0 9.0 Output image disk unit #.
BLC Bottom left corner of output
TRC Top right corner of output
NBOXES 0.0 10.0 Number of boxes to include
BOX 0.0 4096.0 Four coordinates for each box
APARM (1) type of fit
(2) direction of fit.
PIXRANGE Limit fit to pixels in range
Task: Task to read flatten an image by fitting a plane through
the data specified in the boxes.
If no boxes are specified, the entire map is included in
INNAME.....Input image name (name). Standard defaults.
INCLASS....Input image name (class). Standard defaults.
INSEQ......Input image name (seq. #). 0 => highest.
INDISK.....Disk drive # of input image. 0 => any.
OUTNAME....Output image name (name). Standard defaults.
OUTCLASS...Output image name (class). Standard defaults.
OUTSEQ.....Output image name (seq. #). 0 => highest unique.
OUTDISK....Disk drive # of output image. 0 => highest disk
number with sufficient space.
BLC........Bottom left corner of subimage. 0=> all of axis
TRC........Top right corner of subimage. 0=> all of axis
NBOXES.....Number of boxes to include in fit to plane
BOX........Four coordinates for each box
APARM......Specifies the type of fit to perform and fixed
(1) type of fit 0 => subrt. off mean
1 => subrt. off best fit plane
-1 => subrt. off constrained plane
The constrained plane has maximum slope in the
direction APARM(2) measured in degrees CCW from
PIXRANGE...Only pixels within PIXR(1) - PIXR(2) are used in the fit.
PIXR(1) >= PIXR(2) -> full range.
IMFLT: Task which reads an image file and subtracts a best fit
plane to the data. The data included in the fit is
determined by the parameters BOX(I,J), J=1, NBOXES where
I =1,4 provide BLC and TRC for each box. These
parameters are most easilly fit using the verb TVBOX.
The type of fit is determined by APARM
APARM(1) = 0 => only subtrct off the mean value.
= 1 => subtract off the best fit plane.
= -1 => subtract off a plane, but constrain
the direction of the slope using
APARM(2) This is an angle measured in degrees. It
specifies which direction in the output
map should have zero slope. APARM(2) is
only used if APRAM(1) = -1.
A future version of IMFLT should allow higher order
fits and use APARM(5) and APARM(6) as max and min
values for a pixel to be included in the fit.
There are two KNOWN problems with this routine, although
neither one is a major threat to its usefullness.
(1) Not all points included in BOX are used to
determine the fit. The image is truncated
using BLC and TRC before the fit is determined.
(2) If the output image is not flat, because APARM(1)
was set to either -1 or 0, there is some
ambiguity in determining a mean level for the
image. This probably should be the center
of the image. Instead, it is the mean position
of the pixels included in the fit.