如何使用 c++ opencv 找到区域矩形？

Question

I'm use this code for this but I have to find out area of rectangle

import cv2
import numpy as np
import matplotlib.pyplot as plt

whiteblankimage = 255 * np.ones(shape=[60, 60, 3], dtype=np.uint8)

cv2.rectangle(whiteblankimage, pt1=(20,20), pt2=(40,40), color=(0,0,255), thickness=1)

plt.imshow(whiteblankimage)

plt.show()

Answer 1

If pt1 = {.x = 20, .y = 20 } and pt2 = {.x = 40, .y = 40 } and pt1 is a vertex of the rectangle and pt2 the opposite vertex to pt1 , then the width of the rectangle is abs(pt2.x - pt1.x) and the height of the rectangle is abs(pt2.y - pt1.y) , therefore the area is equal to width * height .

In your example: area = abs(40 - 20) * abs(40 - 20) = 20 * 20 = 400 .

But let's be serious, cv::rectangle is a drawing function, not a class. You could use cv::Rect , which has a member function to calculate the area . In addition to that, cv::Rect can be constructed from two points.