如何在OpenCV/python上更改轮廓颜色

Question

我试图在这张图片上画一个不同颜色的轮廓（https://docs.opencv.org/3.4.0/d4/d73/tutorial_py_contours_begin.html），但是轮廓总是白色的。下面是代码

import cv2
import numpy as np

img = cv2.imread(r'C:\Users\Ron Shporer\Desktop\TESTSAVES\TESTLines.png',0)

ret,thresh = cv2.threshold(img,127,255,0)
im2,contours,hierarchy = cv2.findContours(thresh, 1, 2)
cnt = contours[0]
cv2.drawContours(img, contours, -1, (255,0,0), 5)

cv2.namedWindow('img', cv2.WINDOW_NORMAL)
cv2.imshow('img',img)


cv2.waitKey(0)
cv2.destroyAllWindows()`

下图：

Answer 1

试试这个

import cv2
import numpy as np

img = cv2.imread(r'C:\Users\Ron Shporer\Desktop\TESTSAVES\TESTLines.png',0)
img_color = cv2.imread(r'C:\Users\Ron Shporer\Desktop\TESTSAVES\TESTLines.png')

ret,thresh = cv2.threshold(img,127,255,0)
im2,contours,hierarchy = cv2.findContours(thresh, 1, 2)
cnt = contours[0]
cv2.drawContours(img_color , contours, -1, (255,0,0), 5)

cv2.namedWindow('img_color ', cv2.WINDOW_NORMAL)
cv2.imshow('img_color ',img_color )


cv2.waitKey(0)
cv2.destroyAllWindows()

Answer 2

解决办法很简单。您可以将输入图像转换为三通道图像，然后在转换后的彩色图像上绘制轮廓。在

代码应该是这样的：

import cv2
import numpy as np

img = cv2.imread(r'C:\Users\Ron Shporer\Desktop\TESTSAVES\TESTLines.png',0)

ret,thresh = cv2.threshold(img,127,255,0)
im2,contours,hierarchy = cv2.findContours(thresh, 1, 2)
cnt = contours[0]

result_img = cv2.cvtColor(frame, cv2.COLOR_GRAY2RGB)

cv2.drawContours(result_img, contours, -1, (255,0,0), 5)

cv2.namedWindow('img', cv2.WINDOW_NORMAL)
cv2.imshow('img', result_img)

cv2.waitKey(0)
cv2.destroyAllWindows()