绘制形状为（200，200）的Numpy数组显示的是垂直线而不是正方形

Question

我刚刚开始学习Python 3.7.7。

我正在尝试使用图将NIFTI图像显示为带有float32元素的numpy数组。

这是显示图像的代码：

import os
import SimpleITK as sitk
import numpy as np
import matplotlib.pyplot as plt
import cv2

def plot_grey_images_as_figure(img1, img2, title1, title2):
    """
    Show img1 and img2 as a single figure using matplotlib.pylot.

    Show img1 and img2 as a single figure using matplotlib.pylot with the titles
    title1 for img1 and title2 for img2.

    Parameters:
    img1 (array-like or PIL image): Image to show first.
    img2 (array-like or PIL image): Image to show second.
    title1 (string) : Title for image 1.
    title2 (string) : Title for image 2.

    Returns:
    Nothing.

    """    

    plt.subplot(121), plt.imshow(img1, cmap = 'gray')
    plt.title(title1), plt.xticks([]), plt.yticks([])

    plt.subplot(122), plt.imshow(img2, cmap = 'gray')
    plt.title(title2), plt.xticks([]), plt.yticks([])

    plt.show()

    return

这是我在显示图像之前对其进行预处理的方式：

def preprocessing_array(array, rows_standard, cols_standard, debug): # array shape is (48, 240, 240)

    image_rows_Dataset = np.shape(array)[1]   
    image_cols_Dataset = np.shape(array)[2]

    num_rows_1 = ((image_rows_Dataset // 2) - (rows_standard // 2)) #  20
    num_rows_2 = ((image_rows_Dataset // 2) + (rows_standard // 2)) # 220
    num_cols_1 = ((image_cols_Dataset // 2) - (cols_standard // 2)) #  20
    num_cols_2 = ((image_cols_Dataset // 2) + (cols_standard // 2)) # 220

    array = array[:, num_rows_1:num_rows_2, num_cols_1:num_cols_2]


    ### ------ New Axis --------------------------------------------------------
    # Add a new axis to denote that this is a one channel image.
    array  = array[..., np.newaxis] 

    return array  # array shape is (48, 200, 200, 1)

要显示图像，我这样做：

# D is a dataset with shape (960, 2, 200, 200, 1) with float32 elements.
print("Shape: ", D[:,0,:][0].shape)
nifti.plot_grey_images_as_figure(D[:,0,:][0][:,-1], D[:,1,:][0][:,-1], "mask", "output")

我得到此输出：

为什么我得到线条而不是正方形？

也许问题是我添加了一个新轴，然后将其删除，因为不允许我绘制形状为(200, 200, 1)的图像。

Answer 1

图像切片不正确。您的绘图功能应为

base = D[:,0,:]
img1 = base[0][:, :, 0] # Shape of (200, 200)
img2 = base[1][:, :, 0]
nifti.plot_grey_images_as_figure(img1, img2, "mask", "output")

Answer 2

使用numpy.sqeeze()删除尺寸一的尺寸。问题在于将图像作为非2D数组传递。 Squeezing帮助我们沿axis=2放置尺寸，使形状从(200, 200, 1) to (200, 200)。

import numpy as np
np.queeze(D[:,0,:][0], axis=2).shape
# (200, 200)

参考

1. numpy.squeeze() documentation