Fixes Agg/Cairo antialiased rendering of contourf/pcolor/pcolormesh by using a blend group - #32256

import matplotlib
#matplotlib.use('TkCairo')

import numpy as np

import matplotlib.pyplot as plt

x = np.arange(1, 6)
y = x.reshape(-1, 1)
data = (x * y).astype(float)
data[2, 2] = np.nan

fig, axs = plt.subplots(1, 3, figsize=(5, 2), layout="constrained")

for i, antialiased in enumerate([None, False, True]):
    kwargs = {'cmap': 'jet', 'alpha': 0.5}
    if antialiased is not None:
        kwargs['antialiased'] = antialiased

    axs[i].contourf(data, levels=np.arange(1, 25, 1), extend="both", **kwargs)

    axs[i].set_aspect("equal")
    axs[i].set_axis_off()
    axs[i].set_title(f"antialiased={antialiased}")

plt.show()

import matplotlib
#matplotlib.use('TkCairo')

import numpy as np

import matplotlib.pyplot as plt
from matplotlib.transforms import Affine2D

N = 5
data = np.arange(N**2, dtype=float).reshape((N, N))
data[2, 2] = np.nan

x, y = np.meshgrid(np.arange(N + 1), np.arange(N + 1))

rotation = Affine2D().rotate(1)

fig, axs = plt.subplots(2, 3, figsize=(5, 3.5), layout="constrained")

for i, antialiased in enumerate([None, False, True]):
    kwargs = {'cmap': 'jet', 'alpha': 0.5}
    if antialiased is not None:
        kwargs['antialiased'] = antialiased

    axs[0, i].pcolormesh(x, y, data, transform=rotation + axs[0, i].transData,
                         **kwargs)
    axs[1, i].pcolor(x, y, data, transform=rotation + axs[1, i].transData, **kwargs)

    for j in range(2):
        axs[j, i].set_aspect("equal")
        axs[j, i].set_axis_off()
    axs[0, i].set_title(f"antialiased={antialiased}")

plt.show()