python - 如何找到对象(形状)的方向？ - Python Opencv

Question

我的图像总是这样:




但我需要将它们旋转成这样:



但要做到这一点，我需要找到对象的方向，知道对象的较薄部分必须在左侧。
总之，图像是机翼，机翼的起点必须在左侧，机翼的末端必须在右侧。

我希望有人能给我一个建议，我已经尝试了很多不同的策略，但到目前为止都没有好的结果。

Answer 1

这是 Python/OpenCV 中的一种方式。

阅读图片

转换为灰度

临界点

获取外轮廓

从外轮廓获取 minAreaRect 点和角度

获取旋转矩形的顶点

绘制旋转的矩形

根据需要校正角度

打印角度

保存带有绘制在其上的旋转矩形的图像

输入:

import cv2
import numpy as np

# load image as HSV and select saturation
img = cv2.imread("wing2.png")
hh, ww, cc = img.shape

# convert to gray
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# threshold the grayscale image
ret, thresh = cv2.threshold(gray,0,255,0)

# find outer contour
cntrs = cv2.findContours(thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
cntrs = cntrs[0] if len(cntrs) == 2 else cntrs[1]

# get rotated rectangle from outer contour
rotrect = cv2.minAreaRect(cntrs[0])
box = cv2.boxPoints(rotrect)
box = np.int0(box)

# draw rotated rectangle on copy of img as result
result = img.copy()
cv2.drawContours(result,[box],0,(0,0,255),2)

# get angle from rotated rectangle
angle = rotrect[-1]

# from https://www.pyimagesearch.com/2017/02/20/text-skew-correction-opencv-python/
# the `cv2.minAreaRect` function returns values in the
# range [-90, 0); as the rectangle rotates clockwise the
# returned angle trends to 0 -- in this special case we
# need to add 90 degrees to the angle
if angle < -45:
    angle = -(90 + angle)
 
# otherwise, just take the inverse of the angle to make
# it positive
else:
    angle = -angle

print(angle,"deg")

# write result to disk
cv2.imwrite("wing2_rotrect.png", result)

cv2.imshow("THRESH", thresh)
cv2.imshow("RESULT", result)
cv2.waitKey(0)
cv2.destroyAllWindows()

返回的角度:0.8814040422439575 度
带有旋转矩形的图像: