Some short lines added with plot() are missing in the PNG output depending on DPI #20192
Description
Bug report
Depending on DPI, a figure saved as PNG is missing some short lines.
Code for reproduction
import matplotlib
from matplotlib import pyplot as plt
import numpy as np
matplotlib.use('agg')
# Generate a set of 50 random points.
np.random.seed(0)
all_x, all_y = (np.random.rand(50) for _ in range(2))
# Scatter dots in blue.
plt.scatter(all_x, all_y, c='blue', s=2)
# Plot very short lines (length 0.001) in red with a small offset on Y.
for x, y in zip(all_x, all_y):
plt.plot((x, x + 0.001), (y + 0.01, y + 0.01), c='red', linewidth=2)
# Save with different resolutions
plt.savefig('bug_96.png', dpi=96)
plt.savefig('bug_300.png', dpi=300)Actual outcome
Depending on export DPI, some short segments (in red, added by plot()) are missing, while all dots (in blue, added by scatter() are always present).
At 96 DPI:
At 300 DPI:
Expected outcome
The segments should be always present, regardless of the resolution.
Matplotlib version
- Operating system: Ubuntu 20.04.2 LTS
- Matplotlib version (
import matplotlib; print(matplotlib.__version__)): 3.4.2 - Matplotlib backend (
print(matplotlib.get_backend())):agg - Python version: 3.8.5
Python is installed via apt-get, Matplotlib installed system-wide using PIP.