OpenCV 4 with Python Blueprints - Second Edition

Understanding common preprocessing

Before we look at what we have come up with, let's take our time to look at the two most common forms of preprocessing that are almost always applied to any data before machine learning tasks—namely, mean subtraction and normalization.

Mean subtraction is the most common form of preprocessing (sometimes also referred to as zero centering or de-meaning), where the mean value of every feature dimension is calculated across all samples in a dataset. This feature-wise average is then subtracted from every sample in the dataset. You can think of this process as centering the cloud of data on the origin.

Normalization refers to the scaling of data dimensions so that they are of roughly the same scale. This can ...