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michaelhecht on 02/06/16

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detect and measure nested objects with opencv (public)

/ Published in: Python

OpenCV object detection

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import cv2
import numpy as np

#===================================================================
def getObjects(contours,hierarchy):

objs = [] # wichtig wg. Reihenfolge beim plotten
  keys = {}
  
  for i in xrange(len(contours)):
    h = hierarchy[0][i][3]
    a = cv2.contourArea(contours[i])

if h==-1: 
      keys[i] = len(objs)
      objs.append({'out':contours[i],'in':None,'area':a,'id':i})
    else:    
      if keys.has_key(h): 
        k = keys[h]
        objs[k]['in']    = contours[i]
        objs[k]['area'] -= a
      else:
        keys[i] = len(objs)      
        objs.append({'out':contours[i],'in':None,'area':a,'id':i})
      
  return objs
    
#===================================================================
def drawObjects(img,objs,color):

themask  = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)*0
  
  for o in objs:
    cv2.drawContours(themask, [o['out']], -1, 255, -1,lineType=cv2.CV_AA)
    if o.has_key('in'): 
      cv2.drawContours(themask, [o['in']], -1,  0, -1,lineType=cv2.CV_AA)
        
  colored = img.copy()
  cv2.rectangle(colored,(0,0),(colored.shape[1],colored.shape[0]),color,-1)  
  colored = cv2.bitwise_and(colored,colored,mask = themask)

img_masked = cv2.add(img,colored)

return img_masked  
  
#===================================================================

img = cv2.imread('3circ.jpg')

gray = 255-cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

ret,thresh = cv2.threshold(gray,127,255,cv2.THRESH_BINARY)

contours,hierarchy = cv2.findContours(thresh,cv2.RETR_TREE, cv2.CHAIN_APPROX_TC89_KCOS)
for i in xrange(len(hierarchy[0])):
  print i,":",hierarchy[0][i]

objs = getObjects(contours,hierarchy)
img1 = img.copy()
for o in objs: 
  img1 = drawObjects(img1,[o],(0,200,0))
  x,y,w,h = cv2.boundingRect(o['out'])
  text = "A[%i]=%.0f" % (o['id'],o['area'])
  cv2.putText(img1,text,(x,y),cv2.FONT_HERSHEY_SIMPLEX,1,(200,0,200),2,lineType=cv2.CV_AA)
  
all = np.concatenate((img,img1), axis=0)

cv2.imshow('result',all)
cv2.imwrite("3circmasked.jpg",all)
cv2.waitKey(0)
cv2.destroyAllWindows()

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