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Python OpenCV | cv2.line() method
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Python | Smile detection using OpenCV

Last Updated : 04 Jan, 2023
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Emotion detectors are used in many industries, one being the media industry where it is important for the companies to determine the public reaction to their products. In this article, we are going to build a smile detector using OpenCV which takes in live feed from webcam. The smile/happiness detector that we are going to implement would be a raw one, there exist many better ways to implement it.
Step # 1: First of all, we need to import the OpenCV library. 
 

import cv2


Step #2: Include the desired haar-cascades.
Haar-cascades are classifiers that are used to detect features (of face in this case) by superimposing predefined patterns over face segments and are used as XML files. In our model, we shall use face, eye and smile haar-cascades, which after downloading need to be placed in the working directory.
All the required Haar-cascades can be found here. 
 

Python3 
face_cascade = cv2.CascadeClassifier(cv2.data.haarcascades +'haarcascade_frontalface_default.xml') eye_cascade = cv2.CascadeClassifier(cv2.data.haarcascades +'haarcascade_eye.xml') smile_cascade = cv2.CascadeClassifier(cv2.data.haarcascades +'haarcascade_smile.xml')

Step #3: 
In this step, we are going to build main function which would be performing the smile detection. 
 

  1. The live feed coming from the webcam/video device is processed frame by frame. We process the gray scale image, as haar-cascades work better on them.
  2. To detect the face, we use: 
     
Python3 
faces  = face_cascade.detectMultiScale(gray, 1.3, 5)

  1. where 1.3 is the scaling factor, and 5 is the number of nearest neighbors. We can adjust these factors as per our convenience/results to improve our detector.
  2. Now for each subsequent face detected, we need to check for smiles. 
     
Python3 
def detect(gray, frame):     faces = face_cascade.detectMultiScale(gray, 1.3, 5)     for (x, y, w, h) in faces:         cv2.rectangle(frame, (x, y), ((x + w), (y + h)), (255, 0, 0), 2)         roi_gray = gray[y:y + h, x:x + w]         roi_color = frame[y:y + h, x:x + w]         smiles = smile_cascade.detectMultiScale(roi_gray, 1.8, 20)          for (sx, sy, sw, sh) in smiles:             cv2.rectangle(roi_color, (sx, sy), ((sx + sw), (sy + sh)), (0, 0, 255), 2)     return frame


Explanations - 
 

  • The face data is stored as tuples of coordinates. Here, x and y define the coordinate of the upper-left corner of the face frame, w and h define the width and height of the frame. 
     
  • The cv2.rectangle function takes in the arguments frame, upper-left coordinates of the face, lower right coordinates, the RGB code for the rectangle (that would contain within it the detected face) and the thickness of the rectangle. 
     
  • The roi_gray defines the region of interest of the face and roi_color does the same for the original frame. 
     
  • In line 7, we apply smile detection using the cascade. 
     


Step #4: 
We define main function in this step. After execution, the function can be terminated by pressing the "q" key. 
 

Python3 
video_capture = cv2.VideoCapture(0) while video_capture.isOpened():    # Captures video_capture frame by frame     _, frame = video_capture.read()       # To capture image in monochrome                         gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)            # calls the detect() function         canvas = detect(gray, frame)         # Displays the result on camera feed                          cv2.imshow('Video', canvas)       # The control breaks once q key is pressed                             if cv2.waitKey(1) & 0xff == ord('q'):                        break  # Release the capture once all the processing is done. video_capture.release()                                  cv2.destroyAllWindows()

Output: 
 


 


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    OpenCV is a vast library that helps in providing various functions for image and video operations. With OpenCV, we can perform operations on the input video. OpenCV also allows us to save that operated video for further usage. For saving images, we use cv2.imwrite() which saves the image to a specif
    4 min read
    Face Detection using Python and OpenCV with webcam
    Face detection is a important application of computer vision that involves identifying human faces in images or videos. In this Article, we will see how to build a simple real-time face detection application using Python and OpenCV where webcam will be used as the input source.Step 1: Installing Ope
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    Opening multiple color windows to capture using OpenCV in Python
    OpenCV is an open source computer vision library that works with many programming languages and provides a vast scope to understand the subject of computer vision.In this example we will use OpenCV to open the camera of the system and capture the video in two different colors. Approach: With the lib
    2 min read
    Python | Play a video in reverse mode using OpenCV
    OpenCV (Open Source Computer Vision) is a computer vision library that contains various functions to perform operations on Images or videos. OpenCV's application areas include : 1) Facial recognition system 2) motion tracking 3) Artificial neural network 4) Deep neural network 5) video streaming etc
    3 min read
    Template matching using OpenCV in Python
    Template matching is a technique for finding areas of an image that are similar to a patch (template). A patch is a small image with certain features. The goal of template matching is to find the patch/template in an image. To find it, the user has to give two input images: Source Image (S) - The im
    6 min read
    Cartooning an Image using OpenCV - Python
    Instead of sketching images by hand we can use OpenCV to convert a image into cartoon image. In this tutorial you'll learn how to turn any image into a cartoon. We will apply a series of steps like:Smoothing the image (like a painting)Detecting edges (like a sketch)Combining both to get a cartoon ef
    2 min read
    Vehicle detection using OpenCV Python
    Vehicle detection is an important application of computer vision that helps in monitoring traffic, automating parking systems and surveillance systems. In this article, we’ll implement a simple vehicle detection system using Python and OpenCV using a pre-trained Haar Cascade classifier and we will g
    3 min read
    Count number of Faces using Python - OpenCV
    Prerequisites: Face detection using dlib and openCV In this article, we will use image processing to detect and count the number of faces. We are not supposed to get all the features of the face. Instead, the objective is to obtain the bounding box through some methods i.e. coordinates of the face i
    3 min read
    Live Webcam Drawing using OpenCV
    Let us see how to draw the movement of objects captured by the webcam using OpenCV. Our program takes the video input from the webcam and tracks the objects we are moving. After identifying the objects, it will make contours precisely. After that, it will print all your drawing on the output screen.
    3 min read
    Detect and Recognize Car License Plate from a video in real time
    Recognizing a Car License Plate is a very important task for a camera surveillance-based security system. We can extract the license plate from an image using some computer vision techniques and then we can use Optical Character Recognition to recognize the license number. Here I will guide you thro
    11 min read
    Essential OpenCV Functions to Get Started into Computer Vision
    Computer vision is a process by which we can understand the images and videos how they are stored and how we can manipulate and retrieve data from them. Computer Vision is the base or mostly used for Artificial Intelligence. Computer-Vision is playing a major role in self-driving cars, robotics as w
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    OpenCV Projects

    Build GUI Application Pencil Sketch from Photo in Python
    In this article, we will cover how to convert images to watercolor sketches and pencil sketch Linux. Sketching and painting are used by artists of many disciplines to preserve ideas, recollections, and thoughts. Experiencing art from painting and sculpting to visiting an art museum—provides a variet
    5 min read
    Python OpenCV - Drowsiness Detection
    The number of fatalities on the road due to drowsiness is very high. Thus python allows the model of deep learning algorithm via including the use of OpenCV. Drowsiness Detection is the detection of a person to check whether the person is feeling sleepy while performing a significant task. This dete
    9 min read
    Face Alignment with OpenCV and Python
    Face Alignment is the technique in which the image of the person is rotated according to the angle of the eyes.  This technique is actually used as a part of the pipeline process in which facial detection is done using the image. This implementation of face alignment can be easily done with the help
    6 min read
    Age Detection using Deep Learning in OpenCV
    The task of age prediction might sound simple at first but it's quite challenging in real-world applications. While predicting age is typically seen as a regression problem this approach faces many uncertainties like camera quality, brightness, climate condition, background, etc. In this article we'
    5 min read
    Right and Left Hand Detection Using Python
    In this article, we are going to see how to Detect Hands using Python. We will use mediapipe and OpenCV libraries in python to detect the Right Hand and Left Hand. We will be using the Hands model from mediapipe solutions to detect hands, it is a palm detection model that operates on the full image
    5 min read
    OpenCV Python: How to detect if a window is closed?
    OpenCV in Python provides a method cv2.getWindowProperty() to detect whether a window is closed or open. getWindowProperty() returns -1 if all windows are closed. This is one of the main problems we face while using the OpenCV package, sometimes it's hard to detect whether the window is open or clos
    2 min read
    Save frames of live video with timestamps - Python OpenCV
    Images are very important data nowadays from which we can obtain a lot of information which will helpful for analysis. Sometimes data to be processed can be in the form of video. To process this kind of data we have to read video extract frames and save them as images. Security camera videos we have
    3 min read
    Detecting low contrast images with OpenCV, scikit-image, and Python
    In this article, we are going to see how to detect low contrast images with OpenCV, scikit-image using Python A low contrast image has the minimal distinction between light and dark parts, making it difficult to tell where an object's boundary begins and the scene's background begins. For example Th
    2 min read
    Animate image using OpenCV in Python
    In this article, we will discuss how to animate an image using python's OpenCV module. Let's suppose we have one image. Using that single image we will animate it in such a way it will appear continuous array of the same image. This is useful in animating the background in certain games. For example
    3 min read
    Drawing a cross on an image with OpenCV
    In this article, we are going to discuss how to draw a cross on an image using OpenCV-Python. We can draw an overlay of two lines one above another to make a cross on an image.   To draw a line on OpenCV, the below function is used. Syntax: cv2.line(image, starting Point, ending Point, color, thickn
    5 min read
    Blur and anonymize faces with OpenCV and Python
    In this article, we are going to see how to Blur and anonymize faces with OpenCV and Python. For this, we will be using Cascade Classifier to detect the faces. Make sure to download the same, from this link: haarcascade_frontalface_default.xml ApproachFirstly, we use a built face detection algorithm
    4 min read
    Face Detection using Cascade Classifier using OpenCV - Python
    Face detection is a important task in computer vision and Haar Cascade classifiers play an important role in making this process fast and efficient. Haar Cascades are used for detecting faces and other objects by training a classifier on positive and negative images.Positive Images: These images con
    3 min read
    Real time object color detection using OpenCV
    In this article, we will discuss how to detect a monochromatic colour object using python and OpenCV. Monochromatic color means light of a single wavelength. We will use the video, captured using a webcam as input and try to detect objects of a single color, especially Blue. But you can detect any c
    4 min read
    Python - Writing to video with OpenCV
    In this article, we will discuss how to write to a video using OpenCV in Python. ApproachImport the required libraries into the working space.Read the video on which you have to write. Syntax: cap = cv2.VideoCapture("path")Create a output file using cv2.VideoWriter_fourcc() method Syntax: output = c
    1 min read
    Add image to a live camera feed using OpenCV-Python
    In this article, we are going to learn how to insert an image in your live camera feed using OpenCV in Python. Stepwise ImplementationStep 1: Importing the libraries CV reads and stores all the images as a NumPy array. We need the NumPy library to manipulate the image and as expected we need the cv2
    4 min read
    Face and Hand Landmarks Detection using Python - Mediapipe, OpenCV
    In this article, we will use mediapipe python library to detect face and hand landmarks. We will be using a Holistic model from mediapipe solutions to detect all the face and hand landmarks. We will be also seeing how we can access different landmarks of the face and hands which can be used for diff
    4 min read
    Emotion Based Music Player - Python Project
    In this article, we will be discussing how can we recommend music based on expressions or say dominant expressions on someone's face. This is a basic project in which we will be using OpenCV, Matplotlib, DeepFace, and Spotify API. Import Packages and ModulesOpenCV: OpenCV is a Python open-source pac
    6 min read
    Realtime Distance Estimation Using OpenCV - Python
    Prerequisite: Introduction to OpenCV In this article, we are going to see how to calculate the distance with a webcam using OpenCV in Python. By using it, one can process images and videos to identify objects, faces, or even the handwriting of a human. This article focuses on detecting objects. We w
    5 min read
    Webcam QR code scanner using OpenCV
    In this article, we're going to see how to perform QR code scanning using a webcam.  Webcam QR CODE Scanner Before starting, You need to know how this process is going to work. Firstly you need to open your webcam, and you've to run your python program to make it ready to scan the QR code. You can t
    3 min read
    Color Identification in Images using Python - OpenCV
    An open-source library in Python, OpenCV is basically used for image and video processing. Not only supported by any system, such as Windows, Linux, Mac, etc. but also it can be run in any programming language like Python, C++, Java, etc. OpenCV also allows you to identify color in images. Don’t you
    3 min read
    Real-Time Edge Detection using OpenCV in Python | Canny edge detection method
    Edge detection is one of the fundamental image-processing tasks used in various Computer Vision tasks to identify the boundary or sharp changes in the pixel intensity. It plays a crucial role in object detection, image segmentation and feature extraction from the image. In Real-time edge detection,
    5 min read
    Opencv Python program for Face Detection
    The objective of the program given is to detect object of interest(face) in real time and to keep tracking of the same object.This is a simple example of how to detect face in Python. You can try to use training samples of any other object of your choice to be detected by training the classifier on
    2 min read
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