CODEWITHSUNDEEP
pythonopencvraspberry-pi
Crispolo Bernardino
Crispolo Bernardino

Reputation: 41

How to Crop biggest rectangle and applying wrap transform

hi can anyone help me to debug my codes i'm working on cropping the biggest rectangle and applying transformation to it. I uploaded the picture so you can see it. im using python 2.7 on raspberry pi and opencv 3.3.0

enter image description here

import cv2
import os
import numpy as np

im = cv2.imread('image.png')

# Use a blurring effect, to (hopefully) remove these high frequency 
#noises.

image_blurred = cv2.GaussianBlur(im,(3,3),0)



#apply a canny edge-detector

edges = cv2.Canny(image_blurred,100,300,apertureSize = 3)



#finding the contours in the image

contours,hierarchy = cv2.findContours(edges,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)



#to find the biggest rectangle. For each contour cnt, first find the 
#convex hull, then use approaxPolyDP to simplify the contour as much as 
#possible.

hull = cv2.convexHull(cnt)
simplified_cnt = cv2.approxPolyDP(hull,0.001*cv2.arcLength(hull,True),True)



#after finding (hopefully) the right quadrilateral, is transforming back 
#to a rectangle. For this you can use findHomography to come up with a 
#transformation matrix.

(H,mask) = cv2.findHomography(cnt.astype('single'),np.array([[[0., 0.]],[[2150., 0.]],[[2150., 2800.]],[[0.,2800.]]],dtype=np.single))



#for the final tranformation on crop image using warpPerspective

final_image = cv2.warpPerspective(image,H,(2150, 2800))

cv2.imshow("Show",final_image)

cv2.waitKey(0)

this is my code but i always getting and error like this.

enter image description here

this is the error i got

Traceback (most recent call last): File "crop.py", line 11, in contours,hierarchy = cv2.findContours(edges,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE) ValueError: too many values to unpack

Upvotes: 0

Views: 483

Answers (1)

user1767754
user1767754

Reputation: 25154

Look at the docs, findContours returns three values, use as following:

im2, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)

Upvotes: 1

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