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ccdcross - cross correlate images with a reference image
ccdcross
[parameter=value]
ccdcross finds the optimal offset one (or
more) images and a reference image based on the cross-correlation between
two images. By selecting a specific center= and half box= size, one can
focus on a specific area, assuming the offset is less than the box-size.
The following parameters are recognized in order; they may
be given in any order if the keyword is also given. Use --help to confirm
this man page is up to date.
- in=ref,im1,...
- Input image files, first image
is the reference image. At least two images need to be given. No default.
- out=im
- Output cross image. No default.
- center=x0,y0
- X-Y Reference center around
which a box (see box= below) is taken. The are 0-based integer pixels. By
default the center of the image is used. Default: center of first input
image.
- box=b2
- Half size of correlation box. The output image is forced to
have an odd pixel size, 2*box+1. The shift between the images should not
exceed box. By default half the mapsize is used.
- clip=c
- Only use values
above this clip level. By default values are not clipped.
- bad=b
- bad value
to ignore. By default there is no bad value recognized.
Only 2D images
are handled.
The WCS is ignored, 0-based pixel coordinates are reported.
Images
should ideally be the same size, but nothing will stop the program from
running off without that. The user is then responsible for computing the
true offsets as all bets are off.
Here two gaussian shaped sources
with noise are created with a small 1 pixel offset from each other.
ccdgen - gauss 1,2 size=128,128 center=64,64 | ccdgen g64 noise spar=0,0.05
in=-
ccdgen - gauss 1,2 size=128,128 center=65,65 | ccdgen g65 noise spar=0,0.05
in=-
ccdcross g64,g65 shift.ccd box=16
...
### nemo Debug Info: Max cross 13.968 @ 16 16
### nemo Debug Info: X,Y mean: 0.393391 0.412221
### nemo Debug Info: X,Y sig: 1.7885 1.76623
### nemo Debug Info: Center at: 0.393391 0.412221
0.393391 0.412221 0.393391 0.412221 16 16 13.968
ccdmath(1NEMO)
, image(5NEMO)
src/image/mics ccdcross.c
Peter Teuben
11-Apr-2022 V0.1 Created PJT
3-aug-2023 V0.2 fix absolute coordinate PJT
18-apr-2024 V0.3 add peak flux in correlation map PJT
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