Vector vs raster output decision in Matplotlib - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output format of matplotlib savefig with vector format

What type of file is produced by this code snippet?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('output.svg')

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('output.svg')

A A plain text file with raw data points

B A vector image file (paths and shapes) like SVG

C A raster image file (pixels) like PNG or JPEG

D A binary executable file

💡 Hint

SVG files store images as shapes and lines, not pixels.

Saving as 'output.svg' produces a vector image file. Vector files store shapes and lines, so they scale without losing quality.

❓ Predict Output

intermediate

Effect of dpi on raster output in matplotlib

What happens when you save a plot as a PNG with dpi=300 compared to dpi=72?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('high_res.png', dpi=300)
plt.savefig('low_res.png', dpi=72)

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('high_res.png', dpi=300)
plt.savefig('low_res.png', dpi=72)

A The low_res.png will have more pixels than high_res.png

B Both files will have the same pixel dimensions and quality

C The high_res.png will have more pixels and better detail than low_res.png

D The dpi setting only affects vector files, not PNG

💡 Hint

DPI means dots per inch, affecting pixel density in raster images.

Higher dpi means more pixels per inch, so the image is sharper and larger in pixel dimensions.

❓ data_output

advanced

Comparing file sizes of vector vs raster outputs

Given a plot saved as 'plot.svg' (vector) and 'plot.png' (raster), which statement about their file sizes is generally true for complex plots?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np
x = np.linspace(0, 10, 1000)
y = np.sin(x)
plt.plot(x, y)
plt.savefig('plot.svg')
plt.savefig('plot.png')

A The PNG file is usually smaller than the SVG for complex plots

B File size depends only on image resolution, not format

C Both files have the same size regardless of plot complexity

D The SVG file is usually smaller than the PNG for complex plots

💡 Hint

Vector files store instructions for shapes, which can grow with complexity.

For complex plots with many points, vector files can become very large because they store every shape and line, while raster files store pixels and can be compressed.

🧠 Conceptual

advanced

Choosing output format for publication-quality figures

Which output format is best for figures that need to be scaled to any size without losing quality in a scientific paper?

A Vector formats like PDF or SVG

B Raster formats like PNG or JPEG

C Plain text files with raw data

D Bitmap formats like BMP

💡 Hint

Think about scaling images without pixelation.

Vector formats store shapes and lines mathematically, so they scale perfectly without losing quality, ideal for publication.

🔧 Debug

expert

Why does saving a plot as PNG with dpi=100 produce a blurry image?

A user saves a matplotlib plot as PNG with dpi=100 but the image looks blurry when zoomed in. Which option explains the cause?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('blurry.png', dpi=100)

A The dpi setting only affects screen display, not saved files

B PNG format is vector and does not support dpi settings

C The plot data is incorrect causing blurriness

D The dpi is too low, resulting in fewer pixels and less detail

💡 Hint

DPI controls pixel density in raster images.

Low dpi means fewer pixels per inch, so the image looks blurry when zoomed or printed large.