sitk。GetArrayFromImage返回空numpy数组?

我正在处理3D MR图像数据。为了计算直方图,我从sitk转换。将图像映射到维度为3的numpy阵列。虽然我可以使用matplotlib显示每个轴向切片,但numpy阵列在所有三维中都是完全空的。 有人能解释一下发生了什么事吗?

import numpy as np
import SimpleITK as sitk
from myshow import myshow

img = sitk.ReadImage("mri.hdr")
nda = sitk.GetArrayFromImage(img)
myshow(img)
print nda

[[[ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  ..., 
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]]

 [[ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  ..., 
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]]

 [[ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  ..., 
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]]

 ..., 
 [[ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  ..., 
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]]

 [[ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  ..., 
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]]

 [[ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  ..., 
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]
  [ 0.  0.  0. ...,  0.  0.  0.]]]

笔记:

• https://github.com/InsightSoftwareConsortium/SimpleITK-Notebooks/blob/master/Python/myshow.py )

• myshow。py使用matplotlib可视化img切片