numpy 如何实现一个正方形边缘区域置为 0

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一张这样的 numpy 矩阵，圆的直径等于正方形变长，我想把圆外的区域都置为 0 或者一个边界值，python 有什么有效的方法吗？
谢谢各位！

NumPy

方形

img

Python

1 replies • 2017-11-03 18:30:37 +08:00

Hzzone

Nov 3, 2017

更新一下解决方法：
```
width, height = pixel_array.shape
y, x = np.ogrid[0:width,0:height]
centerx, centery = (width/2, height/2)
# print(x, y)
mask = ((y - centery)**2 + (x - centerx)**2) > (width/2)**2
print(mask.shape)
pixel_array[mask] = YOUR_BOUNDARY
plt.imshow(pixel_array)
plt.show()
plt.hist(pixel_array.flatten(), bins=80, color='c')
plt.show()
```