Documentation Link

https://matplotlib.org/stable/gallery/images_contours_and_fields/contourf_demo.html

Problem

The contourf demo could use a clear example of how to properly rasterize the output. It may be useful to include this information directly in the contourf documentation.

Here's a minimal example that shows what used to work for me (based on the example in thecontourf demo and the top answer fromstackoverflow), but is now deprecated as of matplotlib 3.8:

import numpy as npimport matplotlib.pyplot as pltdelta = 0.025x = y = np.arange(-3.0, 3.01, delta)X, Y = np.meshgrid(x, y)Z1 = np.exp(-X**2 - Y**2)Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2)Z = (Z1 - Z2) * 2fig, ax = plt.subplots()cont = ax.contourf(X,Y,Z, levels = 100)for c in cont.collections:    c.set_rasterized(True)

This now returns:

MatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.  for c in cont.collections:

It's not obvious to me how I should be rasterizing a contourf for matplotlib>=3.8 (regardless of whether the method I used above was sensical or not...at least it worked).

If I try to apply something similar to what is in the currentrasterization demo, (which I think resulted from#17708 ),

fig2, ax2 = plt.subplots()cont = ax2.contourf(X,Y,Z, levels = 100, rasterized=True)

then I get the following error:

UserWarning: The following kwargs were not used by contour: 'rasterized'  cont = ax2.contourf(X,Y,Z, levels = 100, rasterized=True)

Suggested improvement

1. Include a paragraph and code snippet somewhere inhttps://matplotlib.org/stable/gallery/images_contours_and_fields/contourf_demo.html explaining how to rasterize contourf.

2. maybe include a description of how to rasterize directly in the documentation of contourf