Image colormaps in Matplotlib - Mini Project: Build & Apply

Image colormaps

📖 Scenario: You are working with a grayscale image represented as a 2D array of pixel brightness values. You want to visualize this image using different color styles called colormaps to better understand the details.

🎯 Goal: Create a small 2D array representing a grayscale image, set a colormap name, apply the colormap to the image using matplotlib, and display the colored image.

📋 What You'll Learn

Create a 2D numpy array called image with the exact values [[0, 50, 100], [150, 200, 255]]

Create a variable called cmap_name and set it to the string 'viridis'

Use matplotlib's imshow function with the cmap parameter set to cmap_name to display the image

Use plt.colorbar() to show the color scale next to the image

Use plt.show() to display the final image

💡 Why This Matters

🌍 Real World

Scientists and engineers often use colormaps to visualize grayscale images such as medical scans, satellite photos, or heatmaps to better understand patterns and details.

💼 Career

Knowing how to apply colormaps is useful for data scientists and analysts who need to present image data clearly and effectively in reports and dashboards.

1

Create the grayscale image array

Create a 2D numpy array called image with these exact values: [[0, 50, 100], [150, 200, 255]]

Matplotlib

import numpy as np
import matplotlib.pyplot as plt

# Create the 2D numpy array called image with the exact values
# Your code here

Need a hint?

Use np.array and pass the list of lists with the exact numbers.

2

Set the colormap name

Create a variable called cmap_name and set it to the string 'viridis'

Matplotlib

import numpy as np
import matplotlib.pyplot as plt

image = np.array([[0, 50, 100], [150, 200, 255]])

# Set the colormap name to 'viridis'
# Your code here

Need a hint?

Assign the string 'viridis' to the variable cmap_name.

3

Display the image with the colormap

Use plt.imshow with the image array and set the cmap parameter to cmap_name to display the colored image

Matplotlib

import numpy as np
import matplotlib.pyplot as plt

image = np.array([[0, 50, 100], [150, 200, 255]])
cmap_name = 'viridis'

# Use plt.imshow to display the image with the colormap
# Your code here

Need a hint?

Call plt.imshow with image and cmap=cmap_name.

4

Show the colorbar and display the image

Add plt.colorbar() to show the color scale and then call plt.show() to display the image

Matplotlib

import numpy as np
import matplotlib.pyplot as plt

image = np.array([[0, 50, 100], [150, 200, 255]])
cmap_name = 'viridis'

plt.imshow(image, cmap=cmap_name)

# Add plt.colorbar() and plt.show() below
# Your code here

Need a hint?

Call plt.colorbar() before plt.show() to add the color scale.