How to convert pixel values in excel file into an image?

If you have an Excel .xlsx file you could use openpyxl to read in the values. The Pillow library can be used to build and save the image.

Assuming each value is an 8-bit value, the following approach could be used:

from itertools import chain
from PIL import Image
import openpyxl

wb = openpyxl.load_workbook("image.xlsx")
ws = wb.active
data = list(ws.iter_rows(values_only=True))

rows = len(data)
cols = max(len(row) for row in data)

img = Image.new('L', (cols, rows), color='black')
img.putdata(list(chain.from_iterable(data)))
img.save('output.png')

So for an Excel file containing these values:

You would get a PNG image looking like (enlarged):

If your file is actually in CSV format:

from itertools import chain
from PIL import Image
import csv

data = []

with open('image.csv', newline='') as f_input:
    for row in csv.reader(f_input):
        data.append(list(map(int, row)))
        
rows = len(data)
cols = max(len(row) for row in data)

img = Image.new('L', (cols, rows), color='black')
img.putdata(list(chain.from_iterable(data)))
img.save('output.png')

e.g. image.csv contains:

24,1,4,255,43,2
2,4,6,0,3,2
1,1,255,3,32,5