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Name

ccdcross - cross correlate images with a reference image

Synopsis

ccdcross [parameter=value]

Description

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.

Parameters

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.

Caveat

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.

Examples

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 12.2081 @ 17 17
    ### nemo Debug Info: X,Y mean: -0.00853349 -0.00708124
    ### nemo Debug Info: Shift: 0.991467 0.992919

See Also

ccdmath(1NEMO) , image(5NEMO)

Files

src/image/mics    ccdcross.c

Author

Peter

Teuben

Update History


11-Apr-2022    V0.1 Created    PJT
3-aug-2023    V0.2 fix absolute coordinate    PJT


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