SGNet: Structure Guided Network via Gradient-Frequency Awareness for Depth Map Super-Resolution
(2312.05799)Abstract
Depth super-resolution (DSR) aims to restore high-resolution (HR) depth from low-resolution (LR) one, where RGB image is often used to promote this task. Recent image guided DSR approaches mainly focus on spatial domain to rebuild depth structure. However, since the structure of LR depth is usually blurry, only considering spatial domain is not very sufficient to acquire satisfactory results. In this paper, we propose structure guided network (SGNet), a method that pays more attention to gradient and frequency domains, both of which have the inherent ability to capture high-frequency structure. Specifically, we first introduce the gradient calibration module (GCM), which employs the accurate gradient prior of RGB to sharpen the LR depth structure. Then we present the Frequency Awareness Module (FAM) that recursively conducts multiple spectrum differencing blocks (SDB), each of which propagates the precise high-frequency components of RGB into the LR depth. Extensive experimental results on both real and synthetic datasets demonstrate the superiority of our SGNet, reaching the state-of-the-art. Codes and pre-trained models are available at https://github.com/yanzq95/SGNet.
Overview
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Depth map super-resolution (DSR) is used in various technologies, and this paper introduces an approach that captures high-frequency structural details beyond the spatial domain.
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The proposed SGNet incorporates a Gradient Calibration Module (GCM) and a Frequency Awareness Module (FAM) to leverage gradient and frequency cues for depth enhancement.
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The innovative GCM and FAM capture clear gradient features and embed high-frequency RGB components into depth maps, improving structure and detail.
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SGNet outperforms state-of-the-art DSR methods on both real-world and synthetic datasets, offering significant improvements in depth map quality.
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The paper underscores multi-domain information exploitation's importance in DSR, with SGNet advancing the field and providing public access to its code and models.
Introduction
Depth map super-resolution (DSR) is a technology widely used in various applications such as 3D reconstruction, virtual reality, and augmented reality. Essentially, DSR aims to generate a high-resolution depth map from a low-resolution one. Standard approaches often leverage accompanying high-resolution RGB images to enhance the reconstruction of depth structure. However, due to the inherently fuzzy nature of low-resolution depth, focusing solely on the spatial domain often falls short. Recognizing the limitation, this work introduces a novel approach that additionally harnesses the gradient and frequency domains to extract high-frequency structural details.
Gradient and Frequency Learning
The proposed system, SGNet, includes two novel components: the Gradient Calibration Module (GCM) and the Frequency Awareness Module (FAM).
Gradient Domain
GCM utilizes the clear gradient features of a high-resolution RGB image to rectify and enhance the blurry structure of low-resolution depth maps. This process involves mapping both RGB and low-resolution depth images into a gradient domain and then applying the refined RGB gradient information to improve the depth structure. A gradient-aware loss function further sharpens the structure by reducing the discrepancy between the intermediate features of GCM and the target high-resolution depth in the gradient domain.
Frequency Domain
FAM introduces a series of Spectrum Differencing Blocks (SDB), which operate recursively to embed the high-frequency components of the RGB image into the low-resolution depth. It starts by mapping the RGB and low-resolution depth images into the frequency space, where the difference in high-frequency information between the two is emphasized and merged to enhance the depth map structure. A frequency-aware loss function is also employed to solidify the response of FAM in the frequency space.
Related Work
DSR has been subject to extensive research, with various methods focusing on the spatial domain to leverage the rich structure information of RGB images to aid in depth map reconstruction. However, previous methods have not fully explored the potential of gradient and frequency information. By comparison, SGNet stands out for its innovative use of these domains to guide the structural recovery of depth maps.
Experiments and Results
Comprehensive testing on both real-world and synthetic data sets demonstrates that SGNet surpasses state-of-the-art methods, significantly improving depth map quality. Notably, on multiple benchmarks, SGNet improved upon the next-best methodologies by considerable margins.
Conclusion
SGNet proposes an advanced approach to depth map super-resolution by extending beyond the spatial domain to incorporate insights from gradient and frequency domains. It has shown notable performance gains over existing methods, highlighting the importance of multi-domain information exploitation in DSR tasks. With its publicly available codes and pre-trained models, SGNet is poised to be a valuable contribution to the research community.
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