Single-Image Shadow Removal Using Deep Learning: A Comprehensive Survey

TL;DR

This paper provides the first comprehensive survey of deep learning-based single-image shadow removal methods, covering technical details, advancements, and future directions in the field.

Contribution

It offers an in-depth review of existing deep learning techniques for shadow removal, highlighting progress, challenges, and insights into the evolution of the field.

Findings

Deep learning methods have significantly advanced shadow removal performance.

Performance comparisons show improvements over traditional techniques.

Future directions include better network architectures and training strategies.

Abstract

Shadow removal aims at restoring the image content within shadow regions, pursuing a uniform distribution of illumination that is consistent between shadow and non-shadow regions. {Comparing to other image restoration tasks, there are two unique challenges in shadow removal:} 1) The patterns of shadows are arbitrary, varied, and often have highly complex trace structures, making ``trace-less'' image recovery difficult. 2) The degradation caused by shadows is spatially non-uniform, resulting in inconsistencies in illumination and color between shadow and non-shadow areas. Recent developments in this field are primarily driven by deep learning-based solutions, employing a variety of learning strategies, network architectures, loss functions, and training data. Nevertheless, a thorough and insightful review of deep learning-based shadow removal techniques is still lacking. In this paper, we are the first to provide a comprehensive survey to cover various aspects ranging from technical details to applications. We highlight the major advancements in deep learning-based single-image shadow removal methods, thoroughly review previous research across various categories, and provide insights into the historical progression of these developments. Additionally, we summarize performance comparisons both quantitatively and qualitatively. Beyond the technical aspects of shadow removal methods, we also explore potential future directions for this field.