Draw a bitmap with python from a numpy matrix

Question

I tried to draw a simple 10x10 black image with a single red pixel at the 8,8 coordinate.

This was my attempt:

from PIL import Image
import numpy as np

foo = np.zeros([10,10,3])
foo[8,8] = [255,0,0] # Draw a red pixel
img = Image.fromarray(foo, 'RGB')
img.save('out.png')

Sadly for some reason the entire image stays black (enlarged):

When printing "foo" the [255,0,0] entry is there, so I am confused on what is wrong here.

Lord Baryhobal · Accepted Answer · 2021-10-02 20:15:52Z

2

You need to specify the data type of the numpy array to int8.

So you would have

foo = np.zeros([10,10,3], dtype=np.int8)

answered Oct 2, 2021 at 20:15

Lord Baryhobal

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