Python 2.7 - How to compare two image?

Question

In python 2.7, I want to compare 2 image to the same, How to do this? please show me step by step. Thanks!

Answer 1

There are many ways to do. By using some opensource Library, like OpenCV, Scikit Learn, TensorFlow.

To compare two images, you can do something like Template Matching in OpenCV

import cv2
import numpy as np
from matplotlib import pyplot as plt
img = cv2.imread('img.jpg', 0)
img2 = img.copy()
template  = cv2.imread('img2.jpg', 0)
w, h = template.shape[::-1]
methods = ['cv2.TM_CCOEFF', 'cv2.TM_CCOEFF_NORMED']
for meth in methods:
    img = img2.copy()
    method = eval(meth)

    res = cv2.matchTemplate(img, template, method)
    min_val, max_val, min_loc, max_loc = cv2.minMaxLoc(res)

    if method in [cv2.TM_SQDIFF or cv2. TM_SQDIFF_NORMED]:
        top_left = min_loc
    else:
        top_left = max_loc

    bottom_right = (top_left[0] + w, top_left[1] + h)

    cv2.rectangle(img, top_left, bottom_right, 255,2)

    plt.subplot(121), plt.imshow(res)
    plt.title('Matching Result'), plt.xticks([]), plt.yticks([])
    plt.subplot(122),plt.imshow(img,cmap = 'gray')
    plt.title('Detected Point'), plt.xticks([]), plt.yticks([])
    plt.suptitle(meth)
    plt.show()

or Histogram comparison

import cv2
import numpy as np

base = cv2.imread('test4.jpg')
test1 = cv2.imread('test3.jpg')
test2 = cv2.imread('test5.jpg')

rows,cols = base.shape[:2]

basehsv = cv2.cvtColor(base,cv2.COLOR_BGR2HSV)
test1hsv = cv2.cvtColor(test1,cv2.COLOR_BGR2HSV)
test2hsv = cv2.cvtColor(test2,cv2.COLOR_BGR2HSV)

halfhsv = basehsv[rows/2:rows-1,cols/2:cols-1].copy()  # Take lower half of the base image for testing

hbins = 180
sbins = 255
hrange = [0,180]
srange = [0,256]
ranges = hrange+srange  # ranges = [0,180,0,256]
ranges=None


histbase = cv2.calcHist(basehsv,[0,1],None,[180,256],ranges)
cv2.normalize(histbase,histbase,0,255,cv2.NORM_MINMAX)

histhalf = cv2.calcHist(halfhsv,[0,1],None,[180,256],ranges)
cv2.normalize(histhalf,histhalf,0,255,cv2.NORM_MINMAX)

histtest1 = cv2.calcHist(test1hsv,[0,1],None,[180,256],ranges)
cv2.normalize(histtest1,histtest1,0,255,cv2.NORM_MINMAX)

histtest2 = cv2.calcHist(test2hsv,[0,1],None,[180,256],ranges)
cv2.normalize(histtest2,histtest2,0,255,cv2.NORM_MINMAX)

for i in xrange(5):
    base_base = cv2.compareHist(histbase,histbase,i)
    base_half = cv2.compareHist(histbase,histhalf,i)
    base_test1 = cv2.compareHist(histbase,histtest1,i)
    base_test2 = cv2.compareHist(histbase,histtest2,i)
    print "Method: {0} -- base-base: {1} , base-test1: {2}, base_test2: {3}".format(i,base_base,base_test1,base_test2)