steps to recognize detected faces using opencv library - opencv

I am using OpenCV library and I can detect multiple faces in a video file or using a webcam. Now, I want to recognize those faces.
If any one guide me step by step means what should I do after detecting faces,it will be great for me. I am using C and C++ language.

#KISHAN, You may follow a tutorial with an example of using OpenFace deep learning network. It takes a 96x96 image of human's face and returns 128-dimensional unit vector called embedding vector. You may match two persons by dot product of these embeddings. So this neural network maps faces to multidimensional unit sphere where similar faces are mapped to the closer points.
NOTE: there is a live demo which downloads models (~35MB) if you pressed a Start button.

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Can Google Cloud Vision API label faces?

I am currently using google cloud-vision api for a project. I want to assign a unique ID to a face, so that it automatically detects which IDs any image contains. This way I can know which person is in the image.
Can cloud-vision distinguish faces and return some unique ID for a face?
NO, and as Armin has already mentioned, Google Vision API doesn't support Facial Recognition or Face verification. It only performs face detection on an image. What you can actually do is to use tensorflow to complete what you want. Let me explain for you:
A typical face recognition system (pipeline) consists of couple of phases :
Face detection: which you can do it by using Google Vision API
Facial features extraction: which you can do by using tensorflow to extract facial features and get face embeddings of each detected face from step 1. Extracting the facial features could be done by using pre-trained model which are trained on large datasets like (VGGFace2, CASIA-WebFace).
Face recognition (identification or verification): which you can achieve by using
Tensorflow to read the face embeddings (which are fetched and saved in step 2) from the desk (it could be also fetched from a database, it depends where you have saved them)
Support Vector Machines (SVM) in python to do multi-class classification.
(IMO) The most important things in face recognition systems are correctly detecting faces and correctly extracting facial features. The third step is just a classification problem and it can be done in many ways, you can also for example use the Euclidean distance between the facial embeddings to know if two faces are similar or not (identify).
For the second and the third step you can take a look at FaceNet https://github.com/davidsandberg/facenet
which is great example how you can develop your own facial recognition system based on tensorflow.
The Vision API service offers a Face Detection feature that can be used to detect multiple faces within an image along with the associated key facial attributes such as emotional state or wearing headwear. Based on this, you can get the bounding polygon around the face, the land marks, roll angle, detection confidence, among other properties; however, it is important to note that this feature doesn't support Facial Recognition, which means that it cannot be used to retrieve unique IDs for the faces detected.
In case this feature doesn't cover your current needs, you can use the Send Feedback button, located at the lower left and upper right corners of the service public documentation, as well as take a look the Issue Tracker tool in order to raise a Vision API feature request and notify to Google about this desired functionality.

Using OpenCV to create a Neural network?

I am working on creating a Real-time image processor for a self driving small scale car project for uni, It uses a raspberry pi to get various information to send to the program to base a decision by.
the only stage i have left is to create a Neural network which will view the image displayed from the camera ( i already have to code to send the array of CV_32F values between 0-255 etc.
I have been scouring the internet and cannot seem to find any example code that is related to my specific issue or my kind of task in general (how to implement a neural network of this kind), so my question is is it possible to create a NN of this size in c++ without hard coding it (aka utilising openCv's capabilities): it will need 400 input nodes for each value (from 20x20 image) and produce 4 outputs of left right fwd or backwards respectively.
How would one create a neural network in opencv?
Does openCV provide a backpropogation(training) interface /function or would I have to write this myself.
once it is trained am I correct in assuming I can load the neural network using ANN_MLP load etc? following this pass the live stream frame (as an array of values) to it and it should be able to produce the correct output.
edit:: I have found this OpenCV image recognition - setting up ANN MLP. and It is very simple in comparison to what I want to do, and I am not Sure how to adapt that to my problem.
OpenCV is not a neural network framework and in turn won't find any advanced features. It's far more common to use a dedicated ANN library and combine it with OpenCV. Caffe is a great choice as a computer vision dedicated deep learning framework (with C++ API), and it can be combined with OpenCV.

iOS Use OpenCV to recognise a building

I'm wondering if it is possible to use the OpenCV framework to recognise a building?
For example, if I store an image of a building, is it possible to use OpenCV to detect this building through the iPhone camera?
Thanks!
Detecting known objects such as your building in an image can be done using the features2d module in OpenCV.
It works by detecting key points in the known image and computing a set of descriptors for these that can be compared to the key points and descriptors computed from the unknown scene image by a process known as matching.
The find_obj.py demo in the samples/python2 folder of OpenCV shows how to detect a known object in an image.
There is also a tutorial in the user guide, see http://docs.opencv.org/doc/user_guide/ug_features2d.html
Note that some of the algorithms often used (e.g. SURF and SIFT) are not free, and need to be licensed separately if you use them.
Is possible, but, you have a long road to go.
One way to do this: use visual keypoints to recognise objects.
OpenCV Sift Documentation

3D template matching by opencv

I have a 3D matrix (very large, let call it L) and a 3D small one (very small, let call it S) and want to use OpenCV to find the closest pattern in L.
Does OpenCV do it for me? If yes, how I should use it?
Thanks.
What you need is the Point Cloud Library, which is an open source library to work with 3D data. I can tell you from my experience, that learning to use this library is very similar to learning OpenCV because many developers work for Willow Garage, the main sponsor of OpenCV.
If you go to the PCL tutorials you will find three useful sections to solve your problem:
1) finding features in your 3D point cloud, that you can later use for matching
2) 3D object recognition based on correspondence grouping
3) Point cloud registration using methods like iterative closest point, and feature matching
No, OpenCV doesn't have anything for this.
Do you have sparse pointcloud or just 3-dim matrix?
For 3-dim matrix you can use phase correlation using FFT. Good library is FFTW
OpenCV has added some neat tools to accomplish this kind of task
Surface Matching https://docs.opencv.org/master/d9/d25/group__surface__matching.html
Silhouette based 3D tracking https://docs.opencv.org/master/d4/dc4/group__rapid.html
Convolutional Neural Network https://docs.opencv.org/master/d9/d02/group__cnn__3dobj.html

OpenCV 2.2 image processing

I have to make an application which recognize road signs. I saw that in OpenCV folder there are some XML files for facial recognition but I do not know what that numbers in the XML represents or how they obtained those values. I need to understand this so as I can do my own XML files for road sign recognition.
I do not know much about OpenCV, anyhow I have completed my Final Year Project on Face Recognition using neural networks. Basically I used an algorithm to extract the Facial Portion from a given image. Thereafter I fed that new image (containing only the face) to a neural network that I developed using Matlab. After rigorous improvements, it was a success and by using the Simulation Feature of Matlab it was possible to precisely identify the individual.
Therefore I strongly recommend that you follow the same technique in carrying out this task.
I managed to find some interesting articles related to this topic, here, here , here and here.
What you need is two steps:
detection step
recognition step
for the detection, I suggest you to use cascade classifier that is included with opencv. It's robust and more quick than that of haar trainer. By this step you train the traffic signs to be detected. I found this tutorial that may help you how to prepare your training stuff
by this step you detect your signs . it may detect you some additional false objects in the image, for these undesired objects you can eliminate them by some processing like ratio, or color , or even by adding some negative images.
for the recognition I suggest you to use exactly the opencv's tutorial dedicated for face recognition
here you don't need a lot of modification..

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