Python Opencv drawContour错误 [英] Python Opencv drawContour error

问题描述

可以，但是我的轮廓颜色是黑色.如何将其更改为红色或绿色?

It work, but my contour's color is black. How to change it to red or green?

    import numpy as np
    import cv2
    from matplotlib import pyplot as plt
    img = cv2.imread('1.jpg',0)
    img1 = cv2.imread('5.jpg',0)
    dest = cv2.subtract(img, img1)
    res = cv2.bitwise_not(dest)
    ret , threshold = cv2.threshold(res,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)          
    cv2.namedWindow('thresimage', cv2.WINDOW_NORMAL)
    cv2.imshow('thresimage',threshold)
    _, contours, hierarchy = cv2.findContours(threshold,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
    print "Number of contours detected %d -> "%len(contours)
    cv2.drawContours(threshold,contours,-1,(0,255,0),3)
    cv2.namedWindow('contour', cv2.WINDOW_NORMAL)
    cv2.imshow('contour',threshold)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

在此处输入图片描述

推荐答案

第一:

contours, hierarchy = cv2.findContours(threshold,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)[-2:]

第二

ret , threshold = cv2.threshold(res,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU) 
# ...
cv2.drawContours(threshold,contours,-1,(0,255,0),3)

您在二进制threshed图像上绘制颜色(0,255,0)，那么它将始终是第一个元素0，即黑色.您应该先将灰色转换为BGR，然后再绘制颜色.

You draw in color (0,255,0) on binary threshed image, then it will always be the first element 0, that's black. You should convert gray to BGR first, then draw color.

canvas = cv2.cvtColor(threshold, cv2.COLOR_GRAY2BGR)
cv2.drawContours(canvas,contours,-1,(0,255,0),3)

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