Python Code – Create A Black and White Image using Numpy Array

As you recall – a black and white image can be represented by a 2d array.

The below Python code takes a 2 x 5 array (checker board pattern) and using matplot converts it into an image we can see.

#%%
import matplotlib.pyplot as plt
import numpy as np

# 2d Image Array with data 2 x 5 - Checker Board
imgArray = np.array([[255, 0, 255, 0, 255],
                     [0, 255, 0, 255, 0]])

# Using matplot to load the array into their image display function
plt.imshow(imgArray)

# We need to make sure matplot knows it is a black and white image
plt.gray()

# Shows the Image
plt.show()

What you get is an output that looks like this.

Each element in the array represents a single pixel. Where the element has a value of 0, the pixel will be black. Where the value is 255, the pixel will be white.

Any value in between 0 and 255 will generate a level of gray.

Making something – The Smiley Face

Using the same idea – lets create a 7×7 array that will output a smile face.

#%%
import matplotlib.pyplot as plt
import numpy as np

# 2d Image Array with data 7 x 7 - Smile Face
imgArray = np.array([[255, 255, 255, 255, 255, 255, 255],
                     [255, 0, 255, 255, 255, 0, 255],
                     [255, 255, 255, 255, 255, 255, 255],
                     [255, 255, 255, 255, 255, 255, 255],
                     [255, 0, 255, 255, 255, 0, 255],
                     [255, 255, 0, 0, 0, 255, 255],
                     [255, 255, 255, 255, 255, 255, 255]])

# Using matplot to load the array into their image display function
plt.imshow(imgArray)

# We need to make sure matplot knows it is a black and white image
plt.gray()

# Shows the Image
plt.show()

Run the code and you will get

As we can see. images are nothing more then 2d arrays – there is nothing magical about them. This is an important fact to remember – as anything we want to do with them just requires some math.

One more fun Python project after this one – convert a text document into an image.

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See the Image Processing Table of Contents

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