cm.set_bad() not working for specific values of grayscale and dpi when saving as pdf #20575

# Paste your code here
#
#

import numpy as np
import pandas as pd

from copy import copy
from matplotlib import cm

from matplotlib import pyplot as plt

fig_size_px = (1280, 960)
fig_dpi = 200
fig_size_inch = tuple( fi/fig_dpi for fi in fig_size_px )

n = 1730
m = 1731

data = pd.read_csv( 'Data.csv', index_col=0, engine='c',  dtype=np.float64 ).values

Mask = np.uint8( np.reshape( data[ :, 0 ], ( m, n ) ) )
data = np.reshape( data[ :, 1 ], ( m, n ) )

cmap_jet = copy( cm.jet )
cmap_jet.set_bad( color='0.9' )
# cmap_jet.set_bad( color='0.78' )
# cmap_jet.set_bad( color=(0.9, 0.9, 0.9) )
# cmap_jet.set_bad( color='#d8dcd6' )

fig4 = plt.figure( 4, figsize=fig_size_inch, dpi=fig_dpi, facecolor='w', clear=True, tight_layout=True )
fig4.clf()
ax4 = fig4.add_subplot(111, aspect='equal')
ax4.cla()

data_masked = np.ma.MaskedArray( data, Mask==0 )

h4 = ax4.imshow( data_masked, origin='lower', cmap=cmap_jet, interpolation='Antialiased' )

ax4.get_xaxis().set_visible( False )
ax4.get_yaxis().set_visible( False )

fig4.savefig( 'Plot_Bad.pdf', dpi=fig_dpi*6, format='pdf', transparent=True )
fig4.savefig( 'Plot_Good.pdf', dpi=fig_dpi*5, format='pdf', transparent=True )
plt.show()