TypeError：无法在opencv

Question

您好，我正在关注下一个文档“ https://pysource.com/2018/09/25/simple-shape-detection-opencv-with-python-3/”，但遇到下一个错误：

Traceback (most recent call last):
  File "e:/Proyectos/Detecciondeobjetos/Untitled-1.py", line 9, in <module>
    for cnt in contours:
TypeError: 'NoneType' object is not iterable

这是我的代码：

import cv2
import numpy as np
font = cv2.FONT_HERSHEY_COMPLEX

img = cv2.imread("123.png", cv2.IMREAD_GRAYSCALE)
_, threshold = cv2.threshold(img, 240, 255, cv2.THRESH_BINARY)
_, contours = cv2.findContours(threshold, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)

for cnt in contours:
    approx = cv2.approxPolyDP(cnt, 0.01*cv2.arcLength(cnt, True), True)
    cv2.drawContours(img, [approx], 0, (0), 5)
    x = approx.ravel()[0]
    y = approx.ravel()[1]
    if len(approx) == 3:
        cv2.putText(img, "Triangle", (x, y), font, 1, (0))
    elif len(approx) == 4:
        cv2.putText(img, "Rectangle", (x, y), font, 1, (0))
    elif len(approx) == 5:
        cv2.putText(img, "Pentagon", (x, y), font, 1, (0))
    elif 6 < len(approx) < 15:
        cv2.putText(img, "Ellipse", (x, y), font, 1, (0))
    else:
        cv2.putText(img, "Circle", (x, y), font, 1, (0))

cv2.imshow("shapes", img)

cv2.imshow("Threshold", threshold)

cv2.waitKey(0)

cv2.destroyAllWindows()

this is the image i am using

Answer 1

template<int size> constexpr auto createObj(){ // implicitly constexpr ---v constexpr auto enumArray = []{ Enums enum_array[size] = {}; for(int i = 0; i < size ; i++){ //fill array with e1 and e2 } return enum_array; }(); return []<std::size_t... S>(std::index_sequence<S...>) -> decltype(auto) { return Example<double, enumArray[S]...>(); }(std::make_index_sequence<size>()); }

这样，您的for循环...

template<int size>
constexpr auto createObj(){
    //   implicitly constexpr ---v
    constexpr auto enumArray = []{
        Enums enum_array[size] = {};

        for(int i = 0; i < size ; i++){
            //fill array with e1 and e2
        }

        return enum_array;
    }();

    constexpr auto&& [...allEnums] = enumArray;

    return Example<double, allEnums...>();
}

...与...相同

contours == None

for cnt in contours: pass 不是容器。 for cnt in None: pass 没有2或3或100个可以循环的元素。以下是None

的签名

None

您将其称为：

cv.findContours

我认为您可能已经交换了contours, hierarchy = cv.findContours(image, mode, method[, contours[, hierarchy[, offset]]] ) 和_, contours = cv2.findContours(threshold, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE) 的顺序

无论如何，看起来_, contours的返回值为contours, _