Book Image

Advanced Deep Learning with TensorFlow 2 and Keras - Second Edition

By : Rowel Atienza
Book Image

Advanced Deep Learning with TensorFlow 2 and Keras - Second Edition

By: Rowel Atienza

Overview of this book

Advanced Deep Learning with TensorFlow 2 and Keras, Second Edition is a completely updated edition of the bestselling guide to the advanced deep learning techniques available today. Revised for TensorFlow 2.x, this edition introduces you to the practical side of deep learning with new chapters on unsupervised learning using mutual information, object detection (SSD), and semantic segmentation (FCN and PSPNet), further allowing you to create your own cutting-edge AI projects. Using Keras as an open-source deep learning library, the book features hands-on projects that show you how to create more effective AI with the most up-to-date techniques. Starting with an overview of multi-layer perceptrons (MLPs), convolutional neural networks (CNNs), and recurrent neural networks (RNNs), the book then introduces more cutting-edge techniques as you explore deep neural network architectures, including ResNet and DenseNet, and how to create autoencoders. You will then learn about GANs, and how they can unlock new levels of AI performance. Next, you’ll discover how a variational autoencoder (VAE) is implemented, and how GANs and VAEs have the generative power to synthesize data that can be extremely convincing to humans. You'll also learn to implement DRL such as Deep Q-Learning and Policy Gradient Methods, which are critical to many modern results in AI.
Table of Contents (16 chapters)
14
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15
Index

2. Anchor boxes

From the discussion in the previous section, we learned that object detection must predict both the bounding box region and the category of the object inside it. Suppose for the meantime our focus is on bounding box coordinates estimation.

How can a network predict the coordinates (xmin,ymin) and (xmax,ymax)? A network can make an initial guess such as (0,0) and (w, h) corresponding to the upper left corner pixel coordinates and the lower right corner pixel coordinates of the image. w is the image width, while h is the image height. Then, the network iteratively corrects the estimates by performing regression on the ground truth bounding box coordinates.

Estimating bounding box coordinates using raw pixels is not optimal due to high variance of possible pixel values. Instead of raw pixels, SSD minimizes pixel error values between the ground truth bounding box and predicted bounding box coordinates. For this example, the pixel error values are (xmin...