使用Matplotlib和NumPy在图像上绘制圆圈 [英] Drawing circles on image with Matplotlib and NumPy

问题描述

我有NumPy个数组，它们保存圆心.

I have NumPy arrays which hold circle centers.

import matplotlib.pylab as plt
import numpy as np
npX = np.asarray(X)
npY = np.asarray(Y)
plt.imshow(img)
// TO-DO
plt.show()

如何在图像上的给定位置显示圆圈?

How can I show circles at the given positions on my image?

推荐答案

您可以使用 matplotlib.patches.Circle 补丁进行此操作.

You can do this with the matplotlib.patches.Circle patch.

以您的示例为例，我们需要遍历X和Y数组，然后为每个坐标创建一个圆形补丁.

For your example, we need to loop through the X and Y arrays, and then create a circle patch for each coordinate.

这是在图像顶部放置圆圈的示例(来自 matplotlib.cbook)

Here's an example placing circles on top of an image (from the matplotlib.cbook)

import matplotlib.pyplot as plt
import numpy as np
from matplotlib.patches import Circle

# Get an example image
import matplotlib.cbook as cbook
image_file = cbook.get_sample_data('grace_hopper.png')
img = plt.imread(image_file)

# Make some example data
x = np.random.rand(5)*img.shape[1]
y = np.random.rand(5)*img.shape[0]

# Create a figure. Equal aspect so circles look circular
fig,ax = plt.subplots(1)
ax.set_aspect('equal')

# Show the image
ax.imshow(img)

# Now, loop through coord arrays, and create a circle at each x,y pair
for xx,yy in zip(x,y):
    circ = Circle((xx,yy),50)
    ax.add_patch(circ)

# Show the image
plt.show()

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