Contours -- OpenCV error : Same output for different features like Hull, Rectangle

Question

使用的图片 --

我的代码：

# multiple programs

import cv2
import numpy as np

img = cv2.imread('Dodo.jpg', 0)
ret, thresh = cv2.threshold(img, 127, 255, 0)
img2, contours, hierarchy = cv2.findContours(thresh, 1, 2)

cnt = contours[0]
M = cv2.moments(cnt)
print(M)

cx = int(M['m10']/ M['m00'])
cy = int(M['m01']/ M['m00'])
print("Cx:", cx, "Cy:", cy)

area = cv2.contourArea(cnt)
print("Area:", area)
perimeter = cv2.arcLength(cnt, True)
print("Perimeter:", perimeter)

epsilon = 0.1*cv2.arcLength(cnt,True)
approx = cv2.approxPolyDP(cnt,epsilon,True)
imgapprox = cv2.drawContours(img,[approx],0,(0,0,255),2)

hull = cv2.convexHull(cnt)
imghull =cv2.drawContours(img,[hull],0,(0,0,255),2)

k = cv2.isContourConvex(cnt)
print(k)

x,y,w,h = cv2.boundingRect(cnt)
rectst = cv2.rectangle(img,(x,y),(x+w,y+h),(0,255,0),2)


rect = cv2.minAreaRect(cnt)
box = cv2.boxPoints(rect)
box = np.int0(box)
rectrt =cv2.drawContours(img,[box],0,(0,0,255),2)

cv2.imshow('StraightRect', rectst)
cv2.imshow('RotatedRect', rectrt)
cv2.imshow('Approx', imgapprox)
cv2.imshow('hull', imghull)

cv2.waitKey()
cv2.destroyAllWindows()

OpenCV-Python 版本 3.4.1

所以我正在尝试学习 OpenCV 中的轮廓部分（下面的Link）

Link : https://docs.opencv.org/3.4.1/dd/d49/tutorial_py_contour_features.html

现在所有功能的输出都相同。即这里每个 cv2.imshow 的输出相同。

为什么？错误是什么？如果是覆盖之前的特征，那怎么显示每一个特征？

请帮忙。谢谢:)

Answer 1

您每次都在同一图像中进行更改。在 cv2.drawContours(img.copy ,.......) , cv2.rectangle(img.copy(),.....) 中使用 image.copy() .因此，它们似乎显示出相同的功能，但事实并非如此。此外，由于背景是黑色，您无法正确看到矩形和轮廓

试试这个：

import cv2
import numpy as np

img = cv2.imread('Dodo.jpg')

f1 = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
f1 = cv2.threshold(f1, 120,255, cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]

img2, contours, hierarchy = cv2.findContours(f1, cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)

#ret, thresh = cv2.threshold(img, 127, 255, 0)
#img2, contours, hierarchy = cv2.findContours(thresh, 1, 2)

cnt = contours[0]
M = cv2.moments(cnt)
print(M)

cx = int(M['m10']/ M['m00'])
cy = int(M['m01']/ M['m00'])
print("Cx:", cx, "Cy:", cy)

area = cv2.contourArea(cnt)
print("Area:", area)
perimeter = cv2.arcLength(cnt, True)
print("Perimeter:", perimeter)

epsilon = 0.1*cv2.arcLength(cnt,True)
approx = cv2.approxPolyDP(cnt,epsilon,True)
imgapprox = cv2.drawContours(img.copy(),[approx],0,(0,0,255),2)

hull = cv2.convexHull(cnt)
imghull =cv2.drawContours(img.copy(),[hull],0,(0,0,255),2)

k = cv2.isContourConvex(cnt)
print(k)

x,y,w,h = cv2.boundingRect(cnt)
rectst = cv2.rectangle(img.copy(),(x,y),(x+w,y+h),(0,255,0),2)


rect = cv2.minAreaRect(cnt)
box = cv2.boxPoints(rect)
box = np.int0(box)
rectrt =cv2.drawContours(img.copy(),[box],0,(0,0,255),2)

cv2.imshow('StraightRect', rectst)
cv2.imshow('RotatedRect', rectrt)
cv2.imshow('Approx', imgapprox)
cv2.imshow('hull', imghull)

cv2.waitKey()
cv2.destroyAllWindows()

这是我执行上面代码后得到的结果

Contours -- OpenCV error : Same output for different features like Hull, Rectangle

Contours -- OpenCV error : Same output for different features like Hull, Rectangle

opencv

python-3.x

opencv-contour

opencv-python