为什么我的numpy图像阵列是一维的？

Question

train = []
#train_labels = []
files = glob.glob ("/datasets/mit-cbcl-farerec-database/test/*.pgm") # your image path
for myFile in files:
 image = cv2.imread (myFile)
 train.append (image) 
trainz = np.array(train)
print(trainz.ndim)

我尝试了不同的方式，但都得到了一维数组