Question

我是一个尝试学习opencv的初学者。我已经在ubuntu系统中成功安装了opencv，并试图从Internet运行一些代码，但是遇到了这个问题

# import the necessary packages
from __future__ import print_function
import imutils
import cv2

# load the Tetris block image, convert it to grayscale, and threshold
# the image
print("OpenCV Version: {}".format(cv2.__version__))
image = cv2.imread("tetris_blocks.png")
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
thresh = cv2.threshold(gray, 225, 255, cv2.THRESH_BINARY_INV)[1]

# check to see if we are using OpenCV 2.X or OpenCV 4
if imutils.is_cv2() or imutils.is_cv4():
    (cnts, _) = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
        cv2.CHAIN_APPROX_SIMPLE)

# check to see if we are using OpenCV 3
elif imutils.is_cv3():
    (_, cnts, _) = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
        cv2.CHAIN_APPROX_SIMPLE)

# draw the contours on the image
cv2.drawContours(image, cnts, -1, (240, 0, 159), 3)
cv2.imshow("Image", image)
cv2.waitKey(0)

输出应为图像，但出现以下错误：

runfile('/home/viper_36/pythontemp/temp.py', wdir='/home/viper_36/pythontemp')
OpenCV Version: 4.0.0
Traceback (most recent call last):

  File "<ipython-input-1-202e5c8bcd5b>", line 1, in <module>
    runfile('/home/viper_36/pythontemp/temp.py', wdir='/home/viper_36/pythontemp')

  File "/home/viper_36/anaconda3/lib/python3.6/site-packages/spyder_kernels/customize/spydercustomize.py", line 704, in runfile
    execfile(filename, namespace)

  File "/home/viper_36/anaconda3/lib/python3.6/site-packages/spyder_kernels/customize/spydercustomize.py", line 108, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "/home/viper_36/pythontemp/temp.py", line 11, in <module>
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

error: OpenCV(4.0.0) /io/opencv/modules/imgproc/src/color.cpp:181: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'

Answer 1

错误的最后一行： (-215:Assertion failed) !_src.empty() in function 'cvtColor' 告诉你很多！

“断言”表示软件正在检查某些内容：“如果接下来出现的内容不正确：我将抛出错误。” 接下来的!_src.empty()可以翻译为：“源图像不为空”。这必须为真，否则断言将引发错误。

这全部意味着您提供的图像路径不在图像所在的位置。确保俄罗斯方块图像与您要执行的图像位于同一文件夹中。或使用绝对路径。在Ubuntu中，其外观应类似于/home/<user>/path/to/image/tetris_blocks.png 如果您在文件浏览器中按ctrl-c映像，则将复制绝对路径！

在python中运行Basic OpenCV程序

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