此错误的原因是什么？(-215：断言失败) 函数 'cvtColor' 中的 ！_src.empty()

Question

OpenCV(4.1.2) /io/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'. 

这里出错的原因是什么？

import tensorflow as tf
from keras.layers import Conv2D, Input, ZeroPadding2D, BatchNormalization, Activation, MaxPooling2D, Flatten, Dense
from keras.models import Model, load_model
from keras.callbacks import TensorBoard, ModelCheckpoint
from sklearn.model_selection import train_test_split
from sklearn.metrics import f1_score
from sklearn.utils import shuffle
import cv2
import imutils
import numpy as np
import matplotlib.pyplot as plt
import time
from os import listdir
import pickle
import joblib

%matplotlib inline



def crop_brain_contour(image, plot=False):

grayscale = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
grayscale = cv2.GaussianBlur(grayscale, (5, 5), 0)
threshold_image = cv2.threshold(grayscale, 45, 255, cv2.THRESH_BINARY)[1]
threshold_image = cv2.erode(threshold_image, None, iterations=2)
threshold_image = cv2.dilate(threshold_image, None, iterations=2)

contour = cv2.findContours(threshold_image.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
contour = imutils.grab_contours(contour)
c = max(contour, key=cv2.contourArea)

extreme_pnts_Left = tuple(c[c[:, :, 0].argmin()][0])
extreme_pnts_Right = tuple(c[c[:, :, 0].argmax()][0])
extreme_pnts_Top = tuple(c[c[:, :, 1].argmin()][0])
extreme_pnts_Bot = tuple(c[c[:, :, 1].argmax()][0])

new_image = image[extreme_pnts_Top[1]:extreme_pnts_Bot[1], extreme_pnts_Left[0]:extreme_pnts_Right[0]]            

if plot:
plt.figure()

plt.subplot(1, 2, 1)
plt.imshow(image)

plt.tick_params(axis='both', which='both', 
top=False, bottom=False, left=False, right=False,
labelbottom=False, labeltop=False, labelleft=False, labelright=False)

plt.title('Original Image')

plt.subplot(1, 2, 2)
plt.imshow(new_image)

plt.tick_params(axis='both', which='both', 
top=False, bottom=False, left=False, right=False,
labelbottom=False, labeltop=False, labelleft=False, labelright=False)

plt.title('Cropped Image')

plt.show()

return new_image




ex_img = cv2.imread('/content/drive/MyDrive/Alzheimer/Alzheimer_s Dataset/train/MildDemented/mildDem0.jpg')
ex_new_img = crop_brain_contour(ex_img, True)




ex_img = cv2.imread('/content/drive/MyDrive/Alzheimer/Alzheimer_s Dataset/train/MildDemented/mildDem0.jpg')
ex_new_img = crop_brain_contour(ex_img, True)



def load_data(dir_list, image_size):


X = []
y = []
image_width, image_height = image_size

for directory in dir_list:
for filename in listdir(directory):
print(directory + '/' + filename)

image = cv2.imread(directory + '/' + filename)

image = crop_brain_contour(image, plot=False)


image = image / 255.

X.append(image)

if directory[-3:] == 'train':
y.append([1])
else:
y.append([0])

X = np.array(X)
y = np.array(y)

X, y = shuffle(X, y)

print(f'Number of examples is: {len(X)}')
print(f'X shape is: {X.shape}')
print(f'y shape is: {y.shape}')

return X, y




Alzheimer_s_Dataset = '/content/drive/MyDrive/Alzheimer/Alzheimer_s Dataset/'

Alzheimer_s_Dataset_train = Alzheimer_s_Dataset + 'train' 
Alzheimer_s_Dataset_test = Alzheimer_s_Dataset + 'test'

IMG_WIDTH, IMG_HEIGHT = (128, 128)
#loading dataset
X, y = load_data([Alzheimer_s_Dataset_train, Alzheimer_s_Dataset_test], (IMG_WIDTH, IMG_HEIGHT))

在此之后，它显示cvtColor错误。如果有人知道原因以及如何解决，请告诉我？

Answer 1

当您试图在空图像上使用cv2.cvtColor()方法时，会出现错误。观察：

>>> import cv2
>>> import numpy as np
>>> img = np.uint8([])
>>> img
array([], dtype=uint8)
>>> cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
cv2.error: OpenCV(4.5.1) /tmp/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'
>>> 

代码中出现空图像的可能原因是在不存在的路径上使用了cv2.imread()方法。确保正确定义了路径，其中一种方法是使用os.path.exists()方法：

>>> import os
>>> path = "Folder/images/1.png"
>>> if os.path.exists(path):
...     img = cv2.imread(path)
... else:
...     print("Path does not exist:", path)
... 
>>> 

Answer 2

• 当函数处理null输入时会发生此错误，可能是因为输入未正确输入。请尝试打印图像并检查它是否为空值
• 在调用crop_brain_contour函数的加载数据函数中，请确保正确传递映像的目录
• 尝试修改您的代码，甚至包括图像的扩展名，并确保输入正确的目录。尝试将代码更改为：image = cv2.imread(directory + '/' + filename + 'extension_of_the_image')