python如何获取图像上黑色正方形四个角点坐标

可以使用Python中的OpenCV库来实现。以下是一个简单的例子：

1. 首先，读取图像并将其转换为灰度图像：

import cv2

img = cv2.imread('image.png')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

2. 然后，使用Canny算子进行边缘检测：

edges = cv2.Canny(gray, 50, 150, apertureSize=3)

3. 接下来，使用霍夫变换检测图像中的直线：

lines = cv2.HoughLines(edges, 1, np.pi/180, 200)

4. 对于每个检测到的直线，计算其与图像边界的交点：

for line in lines:
    rho, theta = line[0]
    a = np.cos(theta)
    b = np.sin(theta)
    x0 = a * rho
    y0 = b * rho
    x1 = int(x0 + 1000 * (-b))
    y1 = int(y0 + 1000 * (a))
    x2 = int(x0 - 1000 * (-b))
    y2 = int(y0 - 1000 * (a))

    cv2.line(img, (x1, y1), (x2, y2), (0, 0, 255), 2)

5. 最后，使用这些交点计算出正方形的四个角点坐标：

corners = cv2.goodFeaturesToTrack(gray, 4, 0.01, 10)
corners = np.int0(corners)

for corner in corners:
    x, y = corner.ravel()
    cv2.circle(img, (x, y), 3, (0, 255, 0), -1)

完整代码如下：

import cv2
import numpy as np

img = cv2.imread('image.png')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
edges = cv2.Canny(gray, 50, 150, apertureSize=3)
lines = cv2.HoughLines(edges, 1, np.pi/180, 200)

for line in lines:
    rho, theta = line[0]
    a = np.cos(theta)
    b = np.sin(theta)
    x0 = a * rho
    y0 = b * rho
    x1 = int(x0 + 1000 * (-b))
    y1 = int(y0 + 1000 * (a))
    x2 = int(x0 - 1000 * (-b))
    y2 = int(y0 - 1000 * (a))

    cv2.line(img, (x1, y1), (x2, y2), (0, 0, 255), 2)

corners = cv2.goodFeaturesToTrack(gray, 4, 0.01, 10)
corners = np.int0(corners)

for corner in corners:
    x, y = corner.ravel()
    cv2.circle(img, (x, y), 3, (0, 255, 0), -1)

cv2.imshow('image', img)
cv2.waitKey(0)
cv2.destroyAllWindows()