确定产品的方向，以便在打开

Question

我试图检测产品的方向，所以我可以用这个方向来选择和放置系统

• 我能探测到物体的轮廓
• 我可以计算出轮廓的中心
• 我可以通过在轮廓上拟合一个椭圆来计算角度，但是结果并不稳定

问题是角度的确定，因为产品在最理想的质量方面也是在上侧和下侧。通过拟合椭圆来计算角度是不稳定的。有时向量指向左边，有时指向右边。如下图所示，您可以在下图（https://answers.opencv.org/upfiles/15684659369233735.png）中看到，所绘制的角度线并不总是指向同一方向

以下是我目前的代码：

import cv2
import numpy as np
import math

# read the image

cap = cv2.imread("20190909_170137.jpg")

def nothing(x):
  pass

# create slider
cv2.namedWindow("Trackbars")
hh='Max'
hl='Min'
wnd = 'Colorbars'

cv2.createTrackbar("threshold", "Trackbars", 150, 255, nothing)
cv2.createTrackbar("Houghlines", "Trackbars", 255, 255, nothing)


while True:
    frame = cv2.imread("20190909_170137.jpg", cv2.IMREAD_COLOR)

    scale_percent = 60 # percent of original size
    width = int(frame.shape[1] * scale_percent / 100)
    height = int(frame.shape[0] * scale_percent / 100)
    dim = (width, height)

    # resize image
    frame = cv2.resize(frame, dim, interpolation = cv2.INTER_AREA)

    # create sliders for variables
    l_v = cv2.getTrackbarPos("threshold", "Trackbars")
    u_v = cv2.getTrackbarPos("Houghlines", "Trackbars")

    #convert frame to Black and White
    bw = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    #convert Black and White to binary image
    ret,thresh4 = cv2.threshold(bw,l_v,255,cv2.THRESH_BINARY)

    #find the contours in thresh4
    im2, contours, hierarchy = cv2.findContours(thresh4, cv2.RETR_LIST, cv2.CHAIN_APPROX_NONE)

    #calculate with contour
    for contour in contours:
        #calculate area and moment of each contour
        area = cv2.contourArea(contour)
        M = cv2.moments(contour)

        if M["m00"] > 0:
            cX = int(M["m10"] / M["m00"])
            cY = int(M["m01"] / M["m00"])


        #Use contour if size is bigger then 1000 and smaller then 50000
        if area > 1000:
            if area <50000:
                approx = cv2.approxPolyDP(contour, 0.001*cv2.arcLength(contour, True), True)
                #draw contour
                cv2.drawContours(frame, contour, -1, (0, 255, 0), 3)
                #draw circle on center of contour
                cv2.circle(frame, (cX, cY), 7, (255, 255, 255), -1)
                perimeter = cv2.arcLength(contour,True)
                approx = cv2.approxPolyDP(contour, 0.04 * perimeter, True)
                #fit elipse
                _ ,_ ,angle = cv2.fitEllipse(contour)
                P1x = cX
                P1y = cY
                length = 35

                #calculate vector line at angle of bounding box
                P2x = int(P1x + length * math.cos(math.radians(angle)))
                P2y = int(P1y + length * math.sin(math.radians(angle)))
                 #draw vector line
                cv2.line(frame,(cX, cY),(P2x,P2y),(255,255,255),5)

                #output center of contour
                print  (P1x , P2y, angle)

                #detect bounding box
                rect = cv2.minAreaRect(contour)
                box = cv2.boxPoints(rect)
                box = np.int0(box)
                #draw bounding box
                cv2.drawContours(frame, [box],0,(0,0,255),2)

                #Detect Hull
                hull = cv2.convexHull(contour)
                #draw line
                #img_hull = cv2.drawContours(frame,[hull],0,(0,0,255),2)


      #print (angle)
    #    print (p)

        cv2.imshow("Frame", thresh4)
        key = cv2.waitKey(1)
        cv2.imwrite('thresh4.png',thresh4)
        key = cv2.waitKey(1)
        cv2.imshow("bw2", frame)
        key = cv2.waitKey(1)
        cv2.imwrite('box.png',frame)
        key = cv2.waitKey(1)
        key = cv2.waitKey(1)
        #if key == 27:
         #   break
        break
    #cap.release()
    cv2.destroyAllWindows()

有人知道我怎样才能确保角度（方向）的计算是100%正确的吗

您可以在以下链接中找到示例图片：

https://answers.opencv.org/upfiles/15684700185160563.jpg