Hey, I just ran your code on Google Colab using Matplotlib 3.8.4, and the plot, including the grid lines and labels, looks perfectly sharp and readable.

This makes me think the issue might be specific to your environment, possibly due to:

1. A rendering backend (e.g., inline/Jupyter vs TkAgg)
2. A lower screen resolution or scaling setting

You can try:

• Increasing dpi in plt.subplots(), e.g., dpi=200
• Saving the plot with plt.savefig("plot.png", dpi=300) to confirm sharpness
• Switching Matplotlib backend using:_

import matplotlib
matplotlib.use("TkAgg")

The problem seems to go beyond resolution/sharpness, as features are repeated (e.g "Hour of day" appears three times along the bottom). @PonySubway how are you running your code and showing the figure? If in an IDE the problem may be with the IDE rather than Matplotlib. I agree with @Amit9785 that saving directly to png or switching backend may provide some clues.

This looks like what ever is rendering the png is confusing [channel, row, col] order and [row, col, channel] order.

Based on the code (and no reported backend), I strongly suggest that this is a bug in what ever UI you are using and should be reported to them.

https://matplotlib.org/stable/gallery/user_interfaces/canvasagg.html is a good reference on how to do this most easily. My guess is the backend is using something like https://matplotlib.org/3.1.1/gallery/misc/agg_buffer.html and reshaping it incorrectly.