Image extent and aspect ratio in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the extent parameter control when displaying an image with matplotlib?

The extent parameter sets the bounding box in data coordinates for the image. It controls where the image is placed on the axes by specifying the left, right, bottom, and top limits.

beginner

What is the default behavior of the aspect parameter in matplotlib's imshow()?

By default, aspect='equal' which means each pixel is square and the image is scaled so that the x and y axes have the same length per unit.

intermediate

How does setting aspect='auto' affect an image in matplotlib?

Setting aspect='auto' allows the image to stretch to fill the axes area, ignoring the original pixel aspect ratio. This can distort the image but fits it to the plot size.

beginner

If you want an image to cover the x-axis from 0 to 10 and y-axis from -5 to 5, how would you set the extent parameter?

You would set extent=[0, 10, -5, 5] to place the image exactly within those data coordinate limits on the axes.

intermediate

Why is controlling the aspect ratio important when displaying images in data plots?

Controlling aspect ratio ensures the image is not stretched or squished, preserving the true shape and proportions. This is important for accurate visual interpretation.

What does the extent parameter in imshow() specify?

A The data coordinate limits where the image is placed

B The color map used for the image

C The interpolation method for the image

D The transparency level of the image

The extent parameter defines the bounding box in data coordinates for the image placement.

What happens if you set aspect='auto' in imshow()?

A The image keeps its original pixel aspect ratio

B The image stretches to fill the axes area

C The image is cropped to fit the axes

D The image is displayed in grayscale

aspect='auto' stretches the image to fill the axes, possibly distorting it.

Which aspect setting preserves the square shape of pixels in matplotlib?

A 'auto'

B 'square'

C 'equal'

D 'none'

aspect='equal' keeps pixels square and scales axes equally.

If you want an image to span from x=0 to x=5 and y=0 to y=10, what is the correct extent?

A [0, 5, 0, 10]

B [5, 0, 10, 0]

C [0, 10, 0, 5]

D [10, 0, 5, 0]

The extent is [left, right, bottom, top], so [0, 5, 0, 10] matches the axes limits.

Why might you want to change the aspect ratio when plotting an image?

A To change the image colors

B To fit the image to the plot area without distortion

C To add grid lines to the image

D To adjust the image size and preserve proportions

Changing aspect adjusts image size and preserves or changes proportions.

Explain how the extent parameter affects image placement in matplotlib plots.

Think about how you tell matplotlib where to put the image on the graph.

Describe the difference between aspect='equal' and aspect='auto' when displaying images.

Consider how the image looks when you want it to keep its shape versus fill the plot area.