如何找到图像中物体的中心和角度？

Question

我正在使用 python 和 OpenCV。我试图找到电池的中心和角度：

随机角度的电池图像：

比我有的代码是这样的：

import cv2
import numpy as np


img = cv2.imread('image/baterias2.png')
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
img2 = cv2.imread('image/baterias4.png',0)


minLineLength = 300
maxLineGap = 5

edges = cv2.Canny(img2,50,200)
cv2.imshow('Canny',edges)
lines = cv2.HoughLinesP(edges,1,np.pi/180,80,minLineLength,maxLineGap)
print lines
salida = np.zeros((img.shape[0],img.shape[1]))
for x in range(0, len(lines)):
    for x1,y1,x2,y2 in lines[x]:
        cv2.line(salida,(x1,y1),(x2,y2),(125,125,125),0)#  rgb


cv2.imshow('final',salida)
cv2.imwrite('result/hough.jpg',img)
cv2.waitKey(0)

有什么想法可以解决吗？

Answer 1

几乎与我的其他答案之一相同。PCA 似乎工作正常。

import cv2
import numpy as np

img = cv2.imread("test_images/battery001.png")  #load an image of a single battery
img_gs = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)  #convert to grayscale

#inverted binary threshold: 1 for the battery, 0 for the background
_, thresh = cv2.threshold(img_gs, 250, 1, cv2.THRESH_BINARY_INV)

#From a matrix of pixels to a matrix of coordinates of non-black points.
#(note: mind the col/row order, pixels are accessed as [row, col]
#but when we draw, it's (x, y), so have to swap here or there)
mat = np.argwhere(thresh != 0)

#let's swap here... (e. g. [[row, col], ...] to [[col, row], ...])
mat[:, [0, 1]] = mat[:, [1, 0]]
#or we could've swapped at the end, when drawing
#(e. g. center[0], center[1] = center[1], center[0], same for endpoint1 and endpoint2),
#probably better performance-wise


mat = np.array(mat).astype(np.float32) #have to convert type for PCA

#mean (e. g. the geometrical center) 
#and eigenvectors (e. g. directions of principal components)
m, e = cv2.PCACompute(mat, mean = np.array([]))

#now to draw: let's scale our primary axis by 100, 
#and the secondary by 50

center = tuple(m[0])
endpoint1 = tuple(m[0] + e[0]*100)
endpoint2 = tuple(m[0] + e[1]*50)

red_color = (0, 0, 255)
cv2.circle(img, center, 5, red_color)
cv2.line(img, center, endpoint1, red_color)
cv2.line(img, center, endpoint2, red_color)
cv2.imwrite("out.png", img)