Matplotlib: Rotating a figure (patch) and applying colors in python

问题

I want to apply different transformations to a patch, including rotating and changing the fill color. Hier is the piece of code already inspired by Matplotlib: rotating a patch

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib as mpl
from matplotlib.collections import PatchCollection

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

myAngles=[0, -45, -90]
myColors=[30, 40, 50]
myPatches=[]

for color, angle in zip (myColors,myAngles):
    #r2 = patches.Rectangle((0,0), 20, 40, color=color,  alpha=0.50)
    r2 = patches.Rectangle((0,0), 20, 40)
    t2 = mpl.transforms.Affine2D().rotate_deg(angle) + ax.transData
    r2.set_transform(t2)
    #ax.add_patch(r2)
    myPatches.append(r2)

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

    plt.grid(True)


collection = PatchCollection(myPatches, cmap=mpl.cm.jet, alpha=0.5)
collection.set_array(np.array(myColors))
ax.add_collection(collection)

plt.show()

Unfortunatly, the transformation is lost when I get out of the for loop. If I add the patch to the ax inside the loop, then everything is fine. But I have to do it at the end, because the colors are collected in the loop and should be applied later on.

Advices of any kind are highly appreciated

Cheers

Armel

回答1:

I get this figure:

when I comment out the +ax.transData from the transform definition:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib as mpl
from matplotlib.collections import PatchCollection

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

myAngles=[0, -45, -90]
myColors=[30, 40, 50]
myPatches=[]

for color, angle in zip (myColors,myAngles):
    #r2 = patches.Rectangle((0,0), 20, 40, color=color,  alpha=0.50)
    r2 = patches.Rectangle((0,0), 20, 40)
    t2 = mpl.transforms.Affine2D().rotate_deg(angle) #+ ax.transData
    r2.set_transform(t2)
    #ax.add_patch(r2)
    myPatches.append(r2)

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

    plt.grid(True)


collection = PatchCollection(myPatches, cmap=mpl.cm.jet, alpha=0.5)
collection.set_array(np.array(myColors))
ax.add_collection(collection)

fig.savefig('withoutTransData.png')
plt.show()

来源：https://stackoverflow.com/questions/7467631/matplotlib-rotating-a-figure-patch-and-applying-colors-in-python