I've constructed an image from some FITS files, and I want to save the resultant masked image as another FITS file. Here's my code:
import numpy as np
from astropy.io import fits
import matplotlib.pyplot as plt
#from astropy.nddata import CCDData
from ccdproc import CCDData
hdulist1 = fits.open('wise_neowise_w1-MJpersr.fits')
hdulist2 = fits.open('wise_neowise_w2-MJpersr.fits')
data1_raw = hdulist1[0].data
data2_raw = hdulist2[0].data
# Hide negative values in order to take logs
# Where {condition}==True, return data_raw, else return np.nan
data1 = np.where(data1_raw >= 0, data1_raw, np.nan)
data2 = np.where(data2_raw >= 0, data2_raw, np.nan)
# Calculation and image subtraction
w1mag = -2.5 * (np.log10(data1) - 9.0)
w2mag = -2.5 * (np.log10(data2) - 9.0)
color = w1mag - w2mag
## Find upper and lower 5th %ile of pixels
mask_percent = 5
masked_value_lower = np.nanpercentile(color, mask_percent)
masked_value_upper = np.nanpercentile(color, (100 - mask_percent))
## Mask out the upper and lower 5% of pixels
## Need to hide values outside the range [lower, upper]
color_masked = np.ma.masked_outside(color, masked_value_lower, masked_value_upper)
color_masked = np.ma.masked_invalid(color_masked)
plt.imshow(color)
plt.title('color')
plt.savefig('color.png', overwrite = True)
plt.imshow(color_masked)
plt.title('color_masked')
plt.savefig('color_masked.png', overwrite = True)
fits.writeto('color.fits',
color,
overwrite = True)
ccd = CCDData(color_masked, unit = 'adu')
ccd.write('color_masked.fits', overwrite = True))
hdulist1.close()
hdulist2.close()
When I use matplotlib.pyplot
to imshow
the images color
and color_masked
, they look as I expect:
However, my two output files, color_masked.fits == color.fits. I think somehow I'm not quite understanding the masking process properly. Can anyone see where I've gone wrong?