Bug summary

Following #29340, when a colorbar is added in an inset axes there is still a small mismatch between the frame and the colours of the colorbar, as shown in the test image added at #29340. That test uses the toolkits inset_axes but the problem also appears when using Axes.inset_axes.

Code for reproduction

From #27763 (comment):

import matplotlib.pyplot as plt
import numpy as np

fig, axes = plt.subplots(1, 1, layout='constrained')

x = np.random.randint(100, size=(30, 200))
c = axes.imshow(x, origin='lower', cmap='Reds', aspect=1)
axins1 = axes.inset_axes([0.05, 0.8, 0.2, 0.09])

fig.colorbar(c, cax=axins1, orientation="horizontal")

fig.savefig('test_single.pdf', bbox_inches='tight')

Actual outcome

Expected outcome

Colorbar frame should be lined up with its colours.

Additional information

To reproduce the bug we need

• Rasterized artist in inset_axes
• Saving with bbox_inches='tight'
• Saving as pdf, so perhaps linked to the mixed-mode renderer calling adjust_bbox multiple times via process_figure_for_rasterizing.

Increasing the figure dpi to 300 makes the problem disappear. Also, when I originally wrote the test at #29340 I forgot to set the style. The problem did not show up with classic mode.

I have reproduced with v3.2, so probably this never worked.

Operating system

Ubuntu

Matplotlib Version

main

Matplotlib Backend

QtAgg

Python version

3.12.5

Jupyter version

n/a

Installation

git checkout