（二）模板匹配

OpenCV-Python中的模板匹配

参考https://blog.youkuaiyun.com/giffordy/article/details/93135823

单对象代码

import cv2
import numpy as np
from matplotlib import pyplot as plt
 
img = cv2.imread('messi5.jpg', 0)
img2 = img.copy()
template = cv2.imread('messi_face.jpg', 0)
w, h = template.shape[::-1]
 
# All the 6 methods for comparison in a list
methods = ['cv2.TM_CCOEFF', 'cv2.TM_CCOEFF_NORMED', 'cv2.TM_CCORR',
           'cv2.TM_CCORR_NORMED', 'cv2.TM_SQDIFF', 'cv2.TM_SQDIFF_NORMED']
 
for meth in methods:
    img = img2.copy()
    
    # exec 语句用来执行储存在字符串或文件中的 Python 语句。 
    method = eval(meth)
    
    # Apply template Matching
    res = cv2.matchTemplate(img, template, method)
    min_val, max_val, min_loc, max_loc = cv2.minMaxLoc(res)
    
    # 使用不同的比较方法，对结果的解释不同
    # If the method is TM_SQDIFF or TM_SQDIFF_NORMED, take minimum
    if method in [cv2.TM_SQDIFF, 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.imshow(res, cmap='gray')
    plt.title('Matching Result'), plt.xticks([]), plt.yticks([])
    
    plt.show()

多对象代码

import cv2
import numpy as np
from matplotlib import pyplot as plt
 
img_rgb = cv2.imread('mario.png')
img_gray = cv2.cvtColor(img_rgb, cv2.COLOR_BGR2GRAY)
template = cv2.imread('mario_coin.png', 0)
w, h = template.shape[::-1]
 
res = cv2.matchTemplate(img_gray, template, cv2.TM_CCOEFF_NORMED)
threshold = 0.8
 
# umpy.where(condition[, x, y])
# Return elements, either from x or y, depending on condition.
# If only condition is given, return condition.nonzero().
loc = np.where(res >= threshold)
 
for pt in zip(*loc[::-1]):
    cv2.rectangle(img_rgb, pt, (pt[0] + w, pt[1] + h), (0, 0, 255), 2)
    
cv2.imwrite('res.png', img_rgb)