adder

NAME

adder -- weighted stacking of images


USAGE

adder [flags] images

absolut a false
julian j false
nondomerr d false
nondomima b false
weight w false
wep e false


PARAMETERS

absolut = false
If true, the absolut pixel values of the input images are used.
julian = false
If true, the julian dates and exposure times of the images are taken from the header in order to calculate an mean julian date and a total integration time for the combined image. The claculated values are written to the header of the output added image and the output errorframe.
nondomerr = false
Only useful in combination with wep = true. If nondomerr = false, the output errorframe is zero at each pixel which has a nonvalid value in at least one of the input errorframes. If true, nonvalid pixels in one or more of the input errorframes are not dominant and just not taken into account for the calculation of the output errorframe.
nondomima = false
If false, the output image is zero at each pixel which has a nonvalid value in at least one of the input images. If true, nonvalid pixels in one or more of the input images are not dominant and just not taken into account for the stacking.
weight = false
If true, the keyword ALPHA is read from the header and the images are summed up weighted with this factor. If false, all images are equally weighted.
wep = false
If true, a combined errorframe is created using input errorframes for each of the input images.

DESCRIPTION

The task adder combines a set of input images. If the weight-flag is used the output is a weighted sum with weights taken from the header. If not the output is an equally weighted sum. If the wep-flag is set, the task creates also an output errorframe using input errorframes for each of the input images. The functionality of the task is very simple. The nondomima-flag (nondomerr-flag) regulates, if a nonvalid pixel in one of the input images (one of the input errorframes) is dominant or not, i.e. if it results in a zero value in the output image (output errorframe) or if it is just not taken into account and the pixel value in the output image (output errorframe) is calculated using the values of the remaining input images (input errorframes).
For the input images, all pixels with value "0" are considered as nonvalid. If wep is used all pixels with the value "-1" in the input errorframe are considerd to be saturated pixels. Saturated pixels are always dominant, so if there is a pixel with value "-1" in one or more of the input errorframes, this pixel will be set to "0" in the output image and to "-1" in the output errorframe, no matter if the pixel is saturated or not in the other input errorframes. In the errorframes all pixels with a negative value other than "-1" are considered to be nonvalid. If there is a nonvalid pixel in an input errorframe, the pixel is also marked as nonvalid in the corresponding input image and vice versa.
In order to calculate an average julian date and a total intagration time the julian-flag has to be set. The keywords JUL-DATE and EXPTIME have to exist in the header of all the input images. If the absolut-flag is set, the absolut pixel values of the input images are combined.


OUTPUT

a...
output added image
e.a...
output errorframe of added image

EXAMPLE

adder -j -d -b -w -e stars_*.fits


Task index
This task was implemented by A. Riffeser
Dokumentation maintained by J. Koppenhöfer
This file was last time updated on 24 Feb 2005