Charles Cooper

Charles Cooper


Image Matching result in images where it shouldn't be one (Python opencv tutorial)

I'm working with the following python opencv example:

import cv2
import numpy as np
from matplotlib import pyplot as plt

img = cv2.imread(‘messi5.jpg’,0)
img2 = img.copy()
template = cv2.imread(‘template.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’,

for meth in methods:
img = img2.copy()
method = eval(meth)

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

# 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
    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,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([])

The matching works pretty well on a set of chosen images, which clearly contained the template. My problem is that even in images which clearly doesn’t contain the template a rectangle was drawn. How can I fit the source code, so it can handle image which doesn’t match at all.

Thanks in advance

#python #opencv

What is GEEK

Buddha Community

Zak Dyer


In the document:

It returns a grayscale image, where each pixel denotes how much does the neighbourhood of that pixel match with template
So set a threshold for the res, if there is no similarity in the image, it does nothing.

res = cv2.matchTemplate(img,template,method)
if res<0.8:

Just like in the Template Matching with Multiple Objects part

John David


Your code always shows the best match, regardless of how good the match is.

You could check the value of max_val (or min_val when SQDIFF is used) and only show the match when this value exceeds a certain threshold.

Ray  Patel

Ray Patel


top 30 Python Tips and Tricks for Beginners

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4) Chaining Of Comparison Operators.

5) Print The File Path Of Imported Modules.

6) Return Multiple Values From Functions.

7) Find The Most Frequent Value In A List.

8) Check The Memory Usage Of An Object.

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Today in this tutorial, we will be applying few of the filters to images. Exciting right?

Let’s begin!

Table of Contents

1. Importing Modules

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Lambda function in python: Lambda is a one line anonymous function and lambda takes any number of arguments but can only have one expression and python lambda syntax is

Syntax: x = lambda arguments : expression

Now i will show you some python lambda function examples:

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What is Python imread()?

Importing OpenCV to use Python imread()

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Image formats supported by Python imread() method

#python modules #opencv-python #python imread() #opencv.imread() #python imread(): different ways to load an image using the opencv.imread() method #load an image

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In this tutorial, you’re going to learn a variety of Python tricks that you can use to write your Python code in a more readable and efficient way like a pro.

Let’s get started

Swapping value in Python

Instead of creating a temporary variable to hold the value of the one while swapping, you can do this instead

>>> FirstName = "kalebu"
>>> LastName = "Jordan"
>>> FirstName, LastName = LastName, FirstName 
>>> print(FirstName, LastName)
('Jordan', 'kalebu')

#python #python-programming #python3 #python-tutorials #learn-python #python-tips #python-skills #python-development