Permanent Nan in NP

[Antigr]

need to conduct some analysis of the image, do not go into the questions what this formula is, it does not matter.

import numpy as np
from PIL import Image
#np.seterr(divide='ignore', invalid='ignore')
image=Image.open('E://test.jpg')
imgr,imgg,imgb=image.split()
r=np.asarray(imgr).astype('float64')
g=np.asarray(imgg).astype('float64')
b=np.asarray(imgb).astype('float64')
vari=(g-r)/(g+r-b)
nan=0
a=[]
for i in range (len(vari)):
    for j in range(len(vari[i])):
        if np.isnan(vari[i][j]):
            print ('NAN object',i,j)
            a=[]
            if not np.isnan(vari[i-1][j-1]):
                a.append(vari[i-1][j-1])
            if not np.isnan(vari[i-1][j]):
                a.append(vari[i-1][j])
            if not np.isnan(vari[i-1][j+1]):
                a.append(vari[i-1][j+1])#1st
            if not np.isnan(vari[i][j-1]):
                a.append(vari[i][j-1])
            if not np.isnan(vari[i][j+1]):
                a.append(vari[i][j+1])
            if not np.isnan(vari[i+1][j-1]):
                a.append(vari[i+1][j-1])
            if not np.isnan(vari[i+1][j]):
                a.append(vari[i+1][j])
            if not np.isnan(vari[i+1][j+1]):
                a.append(vari[i+1][j+1])
            a=np.asarray(a)
            print ('array',a,'mean',np.mean(a))
            vari[i][j]=0   
            nan=nan+1
print('TOTAL NAN',nan)
for i in range (len(vari)):
    for j in range(len(vari[i])):
        if np.isnan(vari[i][j]):
            print ('new NAN object',i,j)
s=0
vari=vari.ravel()
vari2=list(vari)
for i in range(len(vari2)):
    s=s+vari[i]

Code explanations: I need to calculate np.std and np.mean of full 2d array. But there is NaN alltime, i tried to delete Nan in loop, and check sum, but it is NaN too