Python OpenCV 图像区域轮廓标记(框选各种小纸条)

import cv2 as cv

src = cv.imread("./demo.jpg")

gray = cv.cvtColor(src, cv.COLOR_BGR2GRAY)
# cv.imshow("src", src)

gray = cv.GaussianBlur(gray, (5, 5), 0)
edges = cv.Canny(gray, 70, 210)

cv.imshow("edged", edges)

contours, hierarchy = cv.findContours(edges.copy(), cv.RETR_LIST, cv.CHAIN_APPROX_SIMPLE)
print(f"轮廓数量：{len(contours)}")

contours = sorted(contours, key = cv.contourArea, reverse = True)[:3]

cv.drawContours(src,contours,-1,(0,0,255),2)

# 遍历轮廓
for c in contours:
	# 计算轮廓近似
	peri = cv.arcLength(c, True)
	approx = cv.approxPolyDP(c, 0.02 * peri, True)

retval = cv2.arcLength(curve, closed)

approxCurve = cv2.approxPolyDP(curve, epsilon, closed[, approxCurve])

# 遍历轮廓
for c in contours:
	# 计算轮廓近似
	peri = cv.arcLength(c, True)
	approx = cv.approxPolyDP(c, 0.02 * peri, True)

	# 当恰好是 4 个角点的时候，获取轮廓。
	if len(approx) == 4:
		screen_cnt = approx
		break

# 结果显示
cv.drawContours(src, [screen_cnt], -1, (0, 0, 255), 2)

# 遍历轮廓
for c in contours:
  # 计算轮廓近似

  approx = cv.approxPolyDP(c, 30, True)

  if len(approx) == 4:
    screen_cnt = approx
    break