使用函数参数索引函数内的2D numpy数组

Say I have a 2D image in python stored in a numpy array and called npimage (1024 times 1024 pixels). I would like to define a function ShowImage, that take as a paramater a slice of the numpy array:

假设我有一个存储在numpy数组中的python中的2D图像,称为npimage(1024倍1024像素)。我想定义一个函数ShowImage,它将一个numpy数组的参数作为参数:

def ShowImage(npimage,SliceNumpy):
    imshow(npimage(SliceNumpy))

such that it can plot a given part of the image, lets say:

这样它可以绘制图像的给定部分,让我们说:

ShowImage(npimage,[200:800,300:500])

would plot the image for lines between 200 and 800 and columns between 300 and 500, i.e.

将绘制图像为200到800之间的行和300到500之间的行,即

imshow(npimage[200:800,300:500])

Is it possible to do that in python? For the moment passing something like [200:800,300:500] as a parameter to a function result in error.

有可能在python中这样做吗?暂时将[200:800,300:500]之类的内容作为参数传递给函数导致错误。

Thanks for any help or link. Greg

感谢您的帮助或链接。格雷格

1 个解决方案

#1

It's not possible because [...] are a syntax error when not directly used as slice, but you could do:

这是不可能的,因为当不直接用作切片时,[...]是语法错误,但您可以这样做:

Give only the relevant sliced image - not with a seperate argument ShowImage(npimage[200:800,300:500]) (no comma)

仅给出相关的切片图像 - 不是单独的参数ShowImage(npimage [200:800,300:500])(无逗号)
or give a tuple of slices as argument: ShowImage(npimage,(slice(200,800),slice(300:500))). Those can be used for slicing inside the function because they are just another way of defining this slice:

或者给出一个切片元组作为参数:ShowImage(npimage,(slice(200,800),slice(300:500)))。这些可以用于在函数内部进行切片,因为它们只是定义此切片的另一种方式:
```
npimage[(slice(200,800),slice(300, 500))] == npimage[200:800,300:500]
```

A possible solution for the second option could be:

第二种选择的可能解决方案可能是:

import matplotlib.pyplot as plt
def ShowImage(npimage, SliceNumpy):
    plt.imshow(npimage[SliceNumpy])
    plt.show()

ShowImage(npimage, (slice(200,800),slice(300, 500)))
# plots the relevant slice of the array.

#1