COOL-CHIC: Coordinate-based Low Complexity Hierarchical Image Codec

TL;DR

COOL-CHIC is a low-complexity, coordinate-based image codec that achieves compression performance comparable to modern MPEG standards with significantly fewer parameters and computations.

Contribution

It introduces a novel, learned coordinate-based hierarchical image codec with minimal parameters, offering an efficient alternative to autoencoders and traditional codecs.

Findings

Achieves compression close to HEVC standards.

Uses only 629 parameters and 680 multiplications per pixel.

Open-source implementation available.

Abstract

We introduce COOL-CHIC, a Coordinate-based Low Complexity Hierarchical Image Codec. It is a learned alternative to autoencoders with 629 parameters and 680 multiplications per decoded pixel. COOL-CHIC offers compression performance close to modern conventional MPEG codecs such as HEVC and is competitive with popular autoencoder-based systems. This method is inspired by Coordinate-based Neural Representations, where an image is represented as a learned function which maps pixel coordinates to RGB values. The parameters of the mapping function are then sent using entropy coding. At the receiver side, the compressed image is obtained by evaluating the mapping function for all pixel coordinates. COOL-CHIC implementation is made open-source.