使用cv2.putText（）在循环外放置文本

Question

I want to put values of area on top of the rectangle. I tried many ways, but failed

import numpy as np
import cv2
import time
font = cv2.FONT_HERSHEY_SIMPLEX
pic=cv2.imread('multiple.jpg')
picGray=cv2.cvtColor(pic,cv2.COLOR_BGR2GRAY)
picBlur= cv2.GaussianBlur(picGray, (21, 21), 0)
_,contours,_=cv2.findContours(picBlur,cv2.RETR_LIST,cv2.CHAIN_APPROX_NONE)
contours=np.array(contours)
for i in range(len(contours)):
area=cv2.contourArea(contours[i])
print(area)
for cnt in contours:
    cv2.drawContours(pic,cnt,-1,(0,255,0),2)
    x,y,w,h = cv2.boundingRect(cnt)
    cv2.rectangle(pic,(x,y),(x+w,y+h),(0,255,0),2)
    cv2.putText(pic,str(area),(x,y-5), font, .5,(255,255,255),1,cv2.LINE_AA)
cv2.imshow('pic',pic)

Image file 'multiple.jpg'

Answer 1

The code below works for me.

import cv2

font = cv2.FONT_HERSHEY_SIMPLEX
pic=cv2.imread('multiple.jpg')
picGray=cv2.cvtColor(pic,cv2.COLOR_BGR2GRAY)
picBlur= cv2.GaussianBlur(picGray, (21, 21), 0)
contours, hierarchy = cv2.findContours(picBlur,cv2.RETR_LIST,cv2.CHAIN_APPROX_NONE)

for cnt in contours:
    area=cv2.contourArea(cnt)
    print(area)
    cv2.drawContours(pic,cnt,-1,(0,255,0),2)
    x,y,w,h = cv2.boundingRect(cnt)
    cv2.rectangle(pic,(x,y),(x+w,y+h),(0,255,0),2)
    cv2.putText(pic,str(area),(x,y-5), font, .5,(255,255,255),1,cv2.CV_AA)
cv2.imshow('pic',pic)
cv2.waitKey()
cv2.destroyAllWindows()

I adapted:

• the first for-loop,
• changed _, contours, _ to contours, hierarchy (so your output of contours wasn't correct, at least for my version of openCV, 2.4.13.6),
• skipped the np.array(contours) line and
• added cv2.waitkey() (necessary when using cv2.imshow() !!) and cv2.destroyAllWindows()