Matplotlib热图：当热图绘制在其上时图像旋转

Question

我正在尝试在图像上绘制热图。 我做了什么：

import matplotlib.pyplot as plt
import numpy as np
import numpy.random
import urllib
#downloading an example image
urllib.urlretrieve("http://tekeye.biz/wp-content/uploads/2013/01/small_playing_cards.png", "/tmp/cards.png")
#reading and plotting the image
im = plt.imread('/tmp/cards.png')
implot = plt.imshow(im)
#generating random data for the histogram
x=numpy.random.normal(500, 100, size=1000)
y=numpy.random.normal(100, 50, size=1000)
heatmap, xedges, yedges = np.histogram2d(x, y, bins=50)
extent = [xedges[0], xedges[-1], yedges[0], yedges[-1]]
plt.imshow(heatmap, extent=extent,alpha=.5)
plt.show()

当我将它们一起绘制时，图像会旋转，上下颠倒，如下所示：

有没有人有解决旧图片的解决方案？

Answer 1

您需要设置origin个实例的imshow。但是，您还需要更改yedges

中的extent

implot = plt.imshow(im,origin='upper')
...
extent = [xedges[0], xedges[-1], yedges[-1], yedges[0]]
plt.imshow(heatmap, extent=extent,alpha=.5,origin='upper')