Latent Modulated Function for Computational Optimal Continuous Image Representation
Authors: Zongyao He, Zhi Jin

The recent work Local Implicit Image Function (LIIF) and subsequent Implicit Neural Representation (INR) based works have achieved remarkable success in Arbitrary-Scale Super-Resolution (ASSR) by using MLP to decode Low-Resolution (LR) features. However these continuous image representations typically implement decoding in High-Resolution (HR) High-Dimensional (HD) space leading to a quadratic increase in computational cost and seriously hindering the practical applications of ASSR. To tackle this problem we propose a novel Latent Modulated Function (LMF) which decouples the HR-HD decoding process into shared latent decoding in LR-HD space and independent rendering in HR Low-Dimensional (LD) space thereby realizing the first computational optimal paradigm of continuous image representation. Specifically LMF utilizes an HD MLP in latent space to generate latent modulations of each LR feature vector. This enables a modulated LD MLP in render space to quickly adapt to any input feature vector and perform rendering at arbitrary resolution. Furthermore we leverage the positive correlation between modulation intensity and input image complexity to design a Controllable Multi-Scale Rendering (CMSR) algorithm offering the flexibility to adjust the decoding efficiency based on the rendering precision. Extensive experiments demonstrate that converting existing INR-based ASSR methods to LMF can reduce the computational cost by up to 99.9% accelerate inference by up to 57x and save up to 76% of parameters while maintaining competitive performance. The code is available at https://github.com/HeZongyao/LMF.