python - Matplotlib: rotating a patch

Question

I wanted to rotate a Rectangle in matplotlib but when I apply the transformation, the rectangle doesn't show anymore:

rect = mpl.patches.Rectangle((0.0120,0),0.1,1000)
t = mpl.transforms.Affine2D().rotate_deg(45)
rect.set_transform(t)

is this a known bug or do I make a mistake?

Answer 1

The patch in the provided code makes it hard to tell what's going on, so I've made a clear demonstration that I worked out from a matplotlib example:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib as mpl

fig = plt.figure()
ax = fig.add_subplot(111)

r1 = patches.Rectangle((0,0), 20, 40, color="blue", alpha=0.50)
r2 = patches.Rectangle((0,0), 20, 40, color="red",  alpha=0.50)

t2 = mpl.transforms.Affine2D().rotate_deg(-45) + ax.transData
r2.set_transform(t2)

ax.add_patch(r1)
ax.add_patch(r2)

plt.xlim(-20, 60)
plt.ylim(-20, 60)

plt.grid(True)

plt.show()