1. Make a Twilio video application ie this one in 9 minutes
2. All the ml5.jscode is in assets/index.js. ml5.js is a handy ML library in the browser built on top of TensorFlow.js which does most of the heavy-lifting and low-level tasks with regard to ML. The Assets folder also has the model I trained to recognize myself wearing a mask or not.

In ML, there are two popular tasks: classification and regression. This project explores the classification problem: given an input of an image, the machine classifies the class/category of an image.

This project uses the pre-trained modelMobileNet to recognize the content of certain images.

This project also uses Feature Extractor, which utilizes the last layer of a neural network, mapping it to the new classes/categories (ie. a person wearing a mask or not). With Feature Extractor, we don’t need to care much about how the model should be trained, the hyperparameters should be adjusted, etc: this is Transfer Learning, which ml5 makes easy for us.

Code

Commented-out code in assets/video.html adds labels and buttons so the user can add images to the ML model: the first category is for no mask, the second is for having a mask. There's also a train button to train the model once you've added enough data, and a save button to save the model for later if you'd like. Lastly, there is a button to begin detecting/running the model so it is not done automatically. This code is commented-out because I already made and trained a model that the app can use--comment out the code if you want to train your own model with your own face!

assets/index.js gets the video source from the Twilio Video feed, makes a FeatureExtractor object from the MobileNet model, and from that FeatureExtractor object, we make a Classification object with the video element as input source. With ml5, classifier.addImage('no') adds no-mask images, and classifier.addImage('yes') adds mask images to the training set so the model will recognize a video image of you wearing a mask from video frames and not just static images. (This code is currently commented out because I saved a model I trained once, I will edit the code to have multiple forks but I had git issues.)

After clicking the train button, the screen shows the lossValue which decreases to eventually reach zero: the lower the loss, the more accurate the model is, and training is done when lossValue is null.

If the trained model is good at detecting mask or no mask, you can use featureExtractor.save() saves the model and can be loaded next time with featureExtractor.load('model.json').