python - OpenCV 错误 : Assertion failed (scn == 3 || scn == 4) in cvtColor

Question

我是 OpenCV 的新手，在运行模板匹配代码时出现断言失败错误。错误信息如下所示

OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cvtColor, 
file /home/travis/miniconda/conda-bld/conda_1485299292920/work/opencv-
3.2.0/modules/imgproc/src/color.cpp, line 9748
Traceback (most recent call last):
File "opencv_basics.py", line 6, in <module>
   img_gray = cv2.cvtColor(img_rgb, cv2.COLOR_BGR2GRAY)
cv2.error: /home/travis/miniconda/conda-
bld/conda_1485299292920/work/opencv-
3.2.0/modules/imgproc/src/color.cpp:9748: error: (-215) scn == 3 || 
scn == 4 in function cvtColor

这是我要运行的代码。

import cv2
import numpy as np

#Template Matching
img_rgb = cv2.imread('opencv-template-matching-python-tutorial.jpg')
img_gray = cv2.cvtColor(img_rgb, cv2.COLOR_BGR2GRAY)

template = cv2.imread('opencv-template-for-matching.jpg',0)
w, h = template.shape[::-1]

res = cv2.matchTemplate(img_gray,template,cv2.TM_CCOEFF_NORMED)
threshold = 0.8
loc = np.where( res >= threshold)

for pt in zip(*loc[::-1]):
    cv2.rectangle(img_rgb, pt, (pt[0] + w, pt[1] + h), (0,255,255), 2)

cv2.imshow('Detected',img_rgb)

所用图像的 gdrive 文件夹链接是 here

我尝试重新安装 opencv3，但没有成功。我正在使用 python 3.5 和 OpenCV 3.2.0。

Answer 1

加载资源始终是一个好习惯，例如读取图像，检查资源是否实际加载。在这种情况下，您应该检查:

img_bgr = cv2.imread('opencv-template-matching-python-tutorial.jpg')
if img_bgr is not None
    img_gray = cv2.cvtColor(img_bgr, cv2.COLOR_BGR2GRAY)

注意:由于在 OpenCV 中默认情况下颜色空间模型是 BGR(不是 RGB)我只是将您的 img_rgb 变量重命名为 img_bgr。