Representation learning finds useful numerical representations of objects from data. In deep learning, these representations are often embeddings: values from a trained network's second-last layer, selected because they preserve information useful for prediction. section 16.5.1
A practical workflow is:
- Train a neural network on a prediction or self-supervised pretext task. section 16.5.1
- Extract embeddings from the second-last layer rather than using the final prediction. section 16.5.1
- Use the embeddings as input to classifiers, regressors, or other predictive models. section 16.5.1
Learning from image transformations
A network can learn to predict whether an image was cropped, discolored, stretched, or rotated. Its second-last-layer values then represent image characteristics for later prediction tasks. section 16.5.1


