In recent years, object detection approaches using deep convolutional neural networks (CNNs) have derived major advances in normal images. However, such success is hardly achieved with rainy images due to lack of visibility. Aiming to bridge this gap, in this article, we present a novel selective features absorption network (SFA-Net) to improve the performance of object detection not only in rainy weather conditions but also in favorable weather conditions. SFA-Net accomplishes this objective by utilizing three subnetworks, where the feature selection subnetwork is concatenated with the object detection subnetwork through the feature absorption subnetwork to form a unified model. To promote further advancement in object detection impaired by rain, we propose a large-scale rainy image dataset, named srRain, which contains both synthetic rainy images and real-world rainy images for training and testing purposes. srRain is comprised of 25,900 rainy images depicting diverse driving scenarios in the presence of rain with a total of 181,164 instances interpreting five common object categories. Experimental results display that our SFA-Net reaches the highest mean average precision (mAP) of 77.53% on a normal image set, 62.52% on a synthetic rainy image set, 37.34% on a collected natural rainy image set, and 32.86% on a published real rainy image set, surpassing current state-of-the-art object detectors and the combination of image deraining and object detection models while retaining a high speed.

Numerous lightweight detection models have been presented in recent years, yet these detectors are inclined to develop for operating under normal weather conditions without adequate studies for rainy conditions. This is one of the causes leads drastically performance degradation of object detectors due to the decrease in visibility. To address above insufficiency, we propose a new and effective approach, named 3FL-Net, to elevate the performance of lightweight object detectors in the presence of rain. Our approach fulfills the goal by closely incorporating four subnetworks, namely feature enhancement subnetwork, feature extraction subnetwork, feature adaptation subnetwork, and lightweight detection subnetwork. The lightweight detection subnetwork achieved the accuracy improvement by learning diverse features from the feature enhancement subnetwork and feature extraction subnetwork via the feature adaptation subnetwork. To further drive the development in object detection induced by rain, we introduce a large-scale driving dataset, called iRain. The full iRain consists of 17,950 real-world rain images, which covers most of the driving scenarios and 85,081 instances explaining five prevalent object classes. Experiment results on divergent rain datasets expose that our 3FL-Net considerably improves the performance of lightweight detectors and surpasses that of the combination models between rain removal and object detection methods.

In recent years, deep convolutional neural networks (CNNs) have been widely applied and have gained considerable success in object detection (OD). However, most of the CNN-based object detectors have been developed to operate under favorable weather conditions, limiting their ability to accurately detect objects in rainy nighttime (RNT) scenes, thereby resulting in low performance. In this work, we introduce a multilevel knowledge transmission network (MKT-Net) to overcome the challenges of detecting objects with the interference of rain and night. Our proposed model accomplishes this objective by collaborating OD with rain removal (RR) and low-illumination enhancement (LE) tasks. Specifically, the MKT-Net is composed of three main subnetworks that share some shallow layers with each other: an OD subnetwork for performing object classification and localization, an RR subnetwork, and an LE subnetwork for generating clear features. To aggregate and transmit multiscale features generated by the RR and LE subnetworks to the OD subnetwork for boosting detection accuracy, we introduce two feature transmission modules with identical architectures. Extensive evaluation on various datasets has demonstrated the effectiveness of our proposed model, which outperformed competing methods by up to 25.43% and 15.26% in mean average precision on a collected RNT dataset and the published rain in driving dataset, respectively, while maintaining high detection speed.

In recent years, object detection has significantly advanced by using deep learning, especially convolutional neural networks. Most of the existing methods have focused on detecting objects under favorable weather conditions and achieved impressive results. However, object detection in the presence of rain remains a crucial challenge owing to the visibility limitation. In this article, we introduce an amalgamating knowledge network (AK-Net) to deal with the problem of detecting objects hampered by rain. The proposed AK-Net obtains performance improvement by associating object detection with visibility enhancement, and it is composed of five subnetworks: rain streak removal (RSR) subnetwork, raindrop removal (RDR) subnetwork, foggy rain removal (FRR) subnetwork, feature transmission (FT) subnetwork, and object detection (OD) subnetwork. Our approach is flexible; it can adopt different object detection models to construct the OD subnetwork for the final inference of objects. The RSR, RDR, and FRR subnetworks are responsible for producing clean features from rain streak, raindrop, and foggy rain images, respectively, and offer them to the OD subnetwork through the FT subnetwork for efficient object prediction. Experimental results indicate that the mean average precision (mAP) achieved by our proposed AK-Net was up to 19.58% and 26.91% higher than those produced using competitive methods on published iRain and RID datasets, respectively, while preserving the fast-running time of the baseline detector.