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ccdstretch - stretching (upscaling) an image cube along a given axis


ccdstretch [parameter=value]


ccdstretch stretches a selected axis from a cube by duplicating its pixel values factor times. This of course causes a step function along the stretched axis, but a subsequent ccdsmooth(1NEMO) can fix this. See EXAMPLES below.

Using compress=t an axis can be binned instead of stretched, with the option if to average the values or sum them.


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.
Input image cube fileName. No default.
Output image cube fileName. No default.
The factor by which the selected axis is stretched. Must be an integer. [Default: 2]
Select the axis to be stretched. Valid are: x,X,1 for the first axis, y,Y,2 for the second and z,Z,3 for the third axis of the cube. Only one axis can be stretched at the time. Default: z
Compress (rebin) instead of stretch? [Default: false].
Average when rebinning in compress mode? [Default: true]


An example of stretching the Z axis of a cube 4 times, and adding some smoothing to make it look less edgy:
  fitsccd cube.fits - | ccdstretch - - 4 z | ccdsmooth - -  nsmooth=2 dir=z | ccdfits
- cube4.fits
Depending how much you stretch, the smoothing function and/or number of times to smooth may need to be changed. In this example the axis is stretched 4 times, and two hanning smoothings are then applied.

If multiple axes need to be stretched, the program currently needs to be run multiple times, for example in a Unix pipe, as only one axis at the time can be stretched. Here is an example of stretching a 2 x 2 x 2 cube into a 4 x 4 x 4 cube:

   ccdgen cube0 noise 0,1 2,2,2
   ccdstretch cube0 - 2 x | ccdstretch - - 2 y | ccdstretch - - 2 z | ccdprint
- x= y= z= label=z pixel=t

See Also

ccdsmooth(1NEMO) , ccdsub(1NEMO) , ccdslice(1NEMO) , image(5NEMO)




Peter Teuben

Update History

17-aug-2023    V0.1 for Stuart Vogel’s rosetta stone cube    PJT
19-aug-2023    V0.5 added compress= and average=        PJT

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