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Convolutional neural network

As explained in The AI Pocket Book

A neural network architecture that applies convolutions and downsampling to learn spatial features from grid-like data such as images.

A convolutional neural network (CNN) processes grid-like data, especially images, by repeatedly filtering and shrinking it until useful spatial features support a category prediction. It assumes that recognizing an object depends more on its parts than on their exact positions. section 1.31

A CNN works in a repeated pipeline:

  • Treats an image as a table of pixel values. section 1.31
  • Applies several convolutions, each using small matrices whose values are learned during training. section 1.31
  • Combines the filtered results into a new image, then downsamples it by spatially shrinking neighboring values. section 1.31
  • Repeats filtering and downsampling so later stages detect increasingly abstract patterns while discarding precise locations. section 1.31

From pixels to a strawberry

Given an image, a CNN might learn filters that blur regions, highlight a color, or detect sharp changes such as diagonal lines. After successive transformations, those patterns support a prediction such as “strawberry.” A 1024 × 1024 image might first shrink to 512 × 512 by averaging groups of neighboring pixels. section 1.31

Figure 1.11 A diffusion model is trained to improve a corrupted image paired with its caption.

A CNN also appears inside conditional diffusion models, where a U-Net-type CNN learns to repair a corrupted image using a text-caption embedding. section 1.32

How The AI Pocket Book covers it

How deep it goes
Explains learned filters, repeated convolutions, downsampling, and spatial abstraction without deriving the mathematics.
Examples
Uses strawberry classification, cat parts, learned visual filters, pixel downsampling, and diffusion-based image repair.
What it assumes
Assumes basic familiarity with images as pixel grids and machine learning, while defining convolutions and learned filters.
What you can do after
Evaluate/understand how CNNs transform pixels into increasingly abstract features for image classification and multimodal generation.
How it connects
Connects convolutions and downsampling with embeddings, transformers, multimodal AI, and machine learning.

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This explainer was generated by Manning's knowledge graph from the text of The AI Pocket Book. The section links point to the parts of the book it draws on.