To use OpenCV/cv2 to compare and mark the differen

问题:

I want to use Python and cv2 to compare 2 images, like below.

(Python 2.7 + Windows)

c:\Original.jpg

c:\Edited.jpg

Pretty straight forward I can do below and save a picture showing the difference:

import cv2 

Original = cv2.imread("c:\\Original.jpg")
Edited = cv2.imread("c:\\Edited.jpg")

diff = cv2.subtract(Original, Edited)

cv2.imwrite("c:\\diff.jpg", diff)

the result is like:

c:\diff.jpg

Further, I want the difference to be shown in a picture, based on the files compared. In another word, I want to have a picture circle or mark the difference, based on “Edited.jpg”. is it possible?

(thinking one of the ways could be, to identify the visible area in the "diff.jpg", then draw a circle for the area in the "Edited.jpg"?)

回答1:

Thanks to Micka's help above. Below is added, and it works.

im = cv2.imread('c:\\diff.jpg')
im1 = cv2.imread('c:\\Edited.jpg')


imgray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
ret,thresh = cv2.threshold(imgray,127,255,0)
contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)

cv2.drawContours(im1, contours, -1, (0,255,0), 1)
cv2.imwrite("c:\\see_this.jpg", im1)

c:\see_this.jpg