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Need simple python script to display INDI captured FITS files

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  • Thank you received: 3

Need simple python script to display INDI captured FITS files was created by R Dan Nafe

I am having trouble displaying RGB FITS files that were captured by my Nikon, using INDI from the Python cli.
Sample code that I have found out on the interwebs don't work very well with 'real' RGB FITS files.

Opening the file and reading the header yields:
Filename: ./M_57_Light_001.fits
No.    Name      Ver    Type      Cards   Dimensions   Format
  0  PRIMARY       1 PrimaryHDU      52   (6016, 4016, 3)   uint8

The first problem that I hacked my way through was the need to 'reshape' the image data after opening it.
image_data = fits.getdata(image_file)
image_data = image_data.reshape(image_data.shape[2],image_data.shape[1],image_data.shape[0])

After reshaping the data, calling
plt.imshow(image_data,origin='lower')
plt.show()
yields a black rectangle.

(when using any image processing program, stars can be seen in the original image, even without stretching, so the image does have visible data)

Does anyone have an actual, simple example of displaying a DSLR-captured , RGB image in FITS format that was written by INDI?

Thanks in advance!
Dan
1 month 1 week ago #99753

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Replied by Aaron Morris on topic Need simple python script to display INDI captured FITS files

Something like this should work. DSLRs are normally in JPEG mode by default with INDI, which is why you are dealing with FITS RGB data. If you switch your camera to RAW mode, this becomes a little more complex with having to debayer and scale the data.
import numpy as np
from astropy.io import fits
import matplotlib.pyplot as plt
 
 
hdulist = fits.open(image_file)
 
image_data = hdulist[0].data
 
# FITS RGB data needs to be reshaped
image_data = np.swapaxes(image_data, 0, 2)
image_data = np.swapaxes(image_data, 0, 1)
 
# image data is now RGB
 
plt.imshow(image_data)
plt.show()
The following user(s) said Thank You: R Dan Nafe
1 month 1 week ago #99757

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Replied by Aaron Morris on topic Need simple python script to display INDI captured FITS files

There is an example of dealing with RAW data here:

indilib.org/forum/development/14007-blob...g-pyindi-client.html
1 month 1 week ago #99759

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Replied by R Dan Nafe on topic Need simple python script to display INDI captured FITS files

Thanks, Aaron, this worked perfectly.
The call to np.swapaxes (twice!) was the thing that was needed.
Last edit: 1 month 1 week ago by R Dan Nafe.
1 month 1 week ago #99791

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Replied by Aaron Morris on topic Need simple python script to display INDI captured FITS files

It is not very obvious, but FITS stores RGB image data with the matrix axes as "color, height, width" where most programs expect "height, width, color". FITS effectively stores 3 monochrome images for R, G, and B (on the first axis). In the scientific world, it was probably more interesting to view each channel separately than as a combined image.

Numpy has some very nice methods for altering matrices.
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1 month 1 week ago #99792

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