FCNet: A Convolutional Neural Network for Arbitrary-Length Exposure Estimation

TL;DR

FCNet is a novel neural network that effectively estimates and corrects exposure in arbitrary-length image sequences by fusing and correcting images at multiple levels of Laplacian Pyramid decomposition, unifying SEC and MEF tasks.

Contribution

The paper introduces FCNet, a unified CNN framework that handles arbitrary-length exposure correction and fusion, bridging the gap between SEC and MEF methods.

Findings

Effective on arbitrary-length sequences including single images.

Outperforms existing methods on benchmark datasets.

Unifies SEC and MEF tasks in a single framework.

Abstract

The photographs captured by digital cameras usually suffer from over or under exposure problems. For image exposure enhancement, the tasks of Single-Exposure Correction (SEC) and Multi-Exposure Fusion (MEF) are widely studied in the image processing community. However, current SEC or MEF methods are developed under different motivations and thus ignore the internal correlation between SEC and MEF, making it difficult to process arbitrary-length sequences with improper exposures. Besides, the MEF methods usually fail at estimating the exposure of a sequence containing only under-exposed or over-exposed images. To alleviate these problems, in this paper, we develop a novel Fusion-Correction Network (FCNet) to tackle an arbitrary-length (including one) image sequence with improper exposures. This is achieved by fusing and correcting an image sequence by Laplacian Pyramid (LP) image decomposition. In each LP level, the low-frequency base component of the input image sequence is fed into a Fusion block and a Correction block sequentially for consecutive exposure estimation, implemented by alternative exposure fusion and correction. The exposure-corrected image in current LP level is upsampled and fused with the high-frequency detail components of the input image sequence in the next LP level, to output the base component for the Fusion and Correction blocks in next LP level. Experiments on the benchmark dataset demonstrate that our FCNet is effective on arbitrary-length exposure estimation, including both SEC and MEF. The code is publicly released at https://github.com/NKUJinLiang/FCNet.