opencv - 在图像中绘制轮廓

Question

我正在尝试围绕图像绘制轮廓。我可以看到正在找到轮廓，但无法绘制轮廓。轮廓的颜色似乎是两种（黑色和白色）颜色之一。

import cv2
import numpy as np
import matplotlib.pyplot as plt
from skimage import io
%matplotlib inline
im = io.imread('http://matlabtricks.com/images/post-35/man.png')
plt.imshow(im)
imgray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
plt.figure()
plt.imshow(imgray)

#Contoured image
ret,thresh = cv2.threshold(imgray, 120,255,cv2.THRESH_BINARY)
image, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
c_img = cv2.drawContours(image, contours, -1, (0, 255, 0), 1)
plt.figure()
plt.imshow(c_img)

Answer 1

您需要在原始图像上绘制，而不是在从 findContuors() 返回的图像上绘制。以下作品。

# Contoured image
ret,thresh = cv2.threshold(imgray, 120,255,cv2.THRESH_BINARY)
contours = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)[-2]
for contour in contours:
   cv2.drawContours(im, contour, -1, (0, 255, 0), 3)
plt.figure()
plt.imshow(im)

Answer 2

这是我的结果：

---

## Read and convert 
img = io.imread('http://matlabtricks.com/images/post-35/man.png')
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

## Find outer contours 
_, cnts, _= cv2.findContours(gray,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)

## Draw 
canvas = np.zeros_like(img)
cv2.drawContours(canvas , contours, -1, (0, 255, 0), 1)

plt.imshow(canvas)