title: Find template / object in image using Open CV Python
body: <p>I'm working on project related to medical tests, in which I need to find out if test is  positive, negative or invalid.
  below is example of my project needs</p>
  <ol>
  <li>input image</li>
  </ol>
  <p><a href="https://i.stack.imgur.com/KGERX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KGERX.jpg" alt="enter image description here" /></a></p>
  <ol start="2">
  <li>check for test result like in below image</li>
  </ol>
  <p><a href="https://i.stack.imgur.com/cLpD9.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cLpD9.jpg" alt="enter image description here" /></a></p>
  <p>I have tried template detection example using OpenCV but its not accurate.</p>
  <p>below is code which i tried</p>
  <pre><code>import cv2 as cv
  import numpy as np
  from matplotlib import pyplot as plt
  img = cv.imread('s4.jpg', 0)
  img2 = img.copy()
  template = cv.imread('sub-2.jpeg', 0)
  w, h = template.shape[::-1]
  # All the 6 methods for comparison in a list
  methods = ['cv.TM_CCOEFF', 'cv.TM_CCOEFF_NORMED', 'cv.TM_CCORR',
             'cv.TM_CCORR_NORMED', 'cv.TM_SQDIFF', 'cv.TM_SQDIFF_NORMED']
  for meth in methods:
      img = img2.copy()
      method = eval(meth)
      # Apply template Matching
      res = cv.matchTemplate(img, template, method)
      min_val, max_val, min_loc, max_loc = cv.minMaxLoc(res)
      # If the method is TM_SQDIFF or TM_SQDIFF_NORMED, take minimum
      if method in [cv.TM_SQDIFF, cv.TM_SQDIFF_NORMED]:
          top_left = min_loc
      else:
          top_left = max_loc
  
      bottom_right = (top_left[0] + w, top_left[1] + h)
      cv.rectangle(img, top_left, bottom_right, 255, 2)
      plt.subplot(121), plt.imshow(res, cmap='gray')
      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()
  </code></pre>