Counting/Detecting Number of rectangles in the given image in image processing using python coding | Rect O'Mania

Let us see Rect O'Mania which means counting of number of rectangles in the given image using python coding.

Question Description

A binary image is one in which each pixel is either white or black. The input in this problem is a
binary image which contains a number of nonoverlapping
white rectangles in a black
background. The rectangles can be in any orientation. You are expected to find the centre of the
rectangle(s) and also find the angle of rotation of each rectangle with respect to the horizontal.
Note: Measure the angle between the axis parallel to the longer edge of the rectangle passing
through centre and measure the angle in anticlockwise
direction from the horizontal.

Input format

<program> <input image>
Example :
<program> input.jpg

Output format

X1, Y1, D1
X2, Y2, D2
Xn, Yn, Dn
N is the number of rectangles detected
Xi is the X coordinate of the i th rectangle
Yi is the Y coordinate of the i th rectangle
Di is the Angle ( See Note Carefully ) in degrees (0 <= D < 180)
N, Xi, Yi, Di are integers. The ordering must be in terms of size ( Largest >
Smallest )
Answers are accepted with an error or +1/1
in the coordinates (i.e., X1,
X+1, X ) and +2/2
the angle.

Python Program

import numpy as np
import cv2
import math
import sys

flag = 0

img = cv2.imread(str(sys.argv[1]))
imgray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
ret1,thresh1 = cv2.threshold(imgray,127,255,cv2.THRESH_BINARY)
ret2,thresh2 = cv2.threshold(imgray,127,255,cv2.THRESH_BINARY_INV)
contoursb1, hierarchyb1 = cv2.findContours(thresh1, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)
contoursb2, hierarchyb2 = cv2.findContours(thresh2, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)

contoursb = contoursb1
if len(contoursb2)>len(contoursb1):
    contoursb = contoursb2

contoursb = sorted(contoursb, key = cv2.contourArea, reverse = True)
print len(contoursb)
for i in range(len(contoursb)):
    M=cv2.moments(cntb) #center of bot
    if M['m00']!=0 :          
        area = cv2.contourArea(cntb)
        rect = cv2.minAreaRect(cntb)
        box =
        p1 = box[0]
        p2 = box[1]
        p3 = box[3]
        n1 = math.sqrt(((p1[0]-p2[0])*(p1[0]-p2[0]))+((p1[1]-p2[1])*(p1[1]-p2[1])))
        n2 = math.sqrt(((p1[0]-p3[0])*(p1[0]-p3[0]))+((p1[1]-p3[1])*(p1[1]-p3[1])))

        if n1<n2:
            x1 = int((p1[0]+p2[0])/2)
            y1 = int((p1[1]+p2[1])/2)
        if n2<n1:
            x1 = int((p1[0]+p3[0])/2)
            y1 = int((p1[1]+p3[1])/2),(x1,y1),1,(0,0,255),7)

        if x1 != xb:
            if angle>=180 :
                angle = angle-180
            if angle<0 :
                angle = -(angle)
        if x1 == xb:
            angle = 90
        perimeter = cv2.arcLength(cntb,True)
        cv2.drawContours(img, contoursb, -1, (255,0,0), 3)
        print xb,yb,angle


The above program works fine withe the following images

-> Let Us Embed <-