Image colormaps in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a colormap in image visualization?

A colormap is a set of colors used to map data values to colors in an image, helping to visualize data intensity or categories clearly.

beginner

Name two common types of colormaps in matplotlib.

Two common types are 'Sequential' colormaps, which show a progression from low to high values, and 'Diverging' colormaps, which highlight deviation from a midpoint.

beginner

How do you apply a colormap to an image in matplotlib?

Use the 'cmap' parameter in functions like imshow(), for example: plt.imshow(image, cmap='viridis').

intermediate

What does the 'viridis' colormap represent?

'Viridis' is a popular sequential colormap that smoothly changes from dark blue to yellow, designed to be perceptually uniform and colorblind-friendly.

intermediate

Why is choosing the right colormap important in data visualization?

The right colormap ensures data patterns are clear, prevents misinterpretation, and makes visualizations accessible to people with color vision differences.

Which matplotlib function is commonly used to display an image with a colormap?

A plot()

B scatter()

C imshow()

D hist()

imshow() displays images and supports the cmap parameter to apply colormaps.

What type of colormap is best for data that diverges around a midpoint?

A Diverging

B Random

C Categorical

D Sequential

Diverging colormaps highlight differences from a central value, useful for data with positive and negative deviations.

Which colormap is designed to be colorblind-friendly and perceptually uniform?

A jet

B viridis

C hot

D cool

'viridis' is designed for perceptual uniformity and accessibility.

How do you specify a colormap when plotting an image in matplotlib?

A palette='viridis'

B color='viridis'

C map='viridis'

D cmap='viridis'

The correct parameter is cmap to set the colormap.

What is the main purpose of using colormaps in image data?

A To map data values to colors for better understanding

B To reduce image size

C To add random colors

D To change image format

Colormaps help translate data values into colors, making patterns easier to see.

Explain what a colormap is and why it is useful in image visualization.

Think about how colors help show differences in data values.

Describe how to apply a colormap to an image using matplotlib and name a popular colormap.

Remember the function and parameter names.