What is opencv

opensource library(C++,python,java) for image processing, recognizance. OpenCV uses ML algorithms to search for faces within a picture. It matches thousands of small patterns and features.

////Ubuntu Installation///
# sudo apt update
# sudo apt install python3-pip
# sudo apt install python3-opencv
      

How opencv works?

1. Breaks task into smaller tasks=classifiers
- Task of image recognization is broken into smaller tasks called Classifiers. For a face, we can have 6000+ Classifiers.
- The algorithm starts at the top left of a picture and moves down across small blocks of data, looking at each block and matching, constantly asking, “Is this a face?
2. Breaking problem in Multiple Stages=Casades
- Cascade dictionary meaning is waterfall. In ML Cascade is breaking the problem of detecting faces into multiple stages. There canbe 30-50 cascades.
- The cascades themselves are a bunch of XML files that contain OpenCV data used to detect objects.

Haar Cascade
- Haar is a supervised learning where ascade function is trained from a lot of positive and negative images. It is then used to detect objects in other images.
- Lets take face detection as an example.
  Initially, the algorithm needs a lot of positive images of faces and negative images without faces to train the classifier Cascade classifier training requires a set of positive samples and a set of negative images.
  You must provide a set of positive images with regions of interest specified to be used as positive samples.
  How it works? The algorithm has four stages: Haar Feature Selection Creating Integral Images Adaboost Training: selects the best features and trains the classifiers that use them Cascading Classifiers