Bug summary

Hi,

I am trying to save a plot to PDF (or SVG) that uses the fill_between function between two time series, and the resulting file is much larger than when plotting each series individually.

Code for reproduction

import numpy as np
import matplotlib.pyplot as plt

rng = np.random.default_rng(seed=424242)

t_max = int(1e5)
t = np.arange(1, t_max+1, dtype=int)

data = rng.normal(size=(10, t_max))

# Lightweight figure (266 kb)
plt.figure(dpi=200)

plt.plot(t, np.min(data, axis=0), color='tab:blue', alpha=0.75)
plt.plot(t, np.max(data, axis=0), color='tab:blue', alpha=0.75)

plt.xlim(1, t_max)
plt.savefig(f"plot_minmax_{t_max}.svg")

# Large figure (1.1 Mb)
plt.figure(dpi=200)
plt.fill_between(t, np.min(data, axis=0), np.max(data, axis=0), color='tab:blue', alpha=0.5)
plt.xlim(1, t_max)
plt.savefig(f"plot_fill_{t_max}.svg")

Actual outcome

Expected outcome

The file size of the file drawn with fill_between() should stay roughly the same as the file drawing the min and the max only.

Additional information

I have plotted the resulting file sizes for different numbers of data points.
The file size of the file generated with fill_between() grows linearly with the number of data points (as could be expected), but not the file size of the file plotting the min and the max directly: maybe there's an optimization in plot() that's not being used in fill_between() ?

Operating system

macOS

Matplotlib Version

3.4.3

Matplotlib Backend

module://matplotlib_inline.backend_inline

Python version

Python 3.9.7

Jupyter version

No response

Installation

pip