HWT-SRNet: Heterogeneous Windows Transformer Network for Image Super-Resolution
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摘要: 在大数据时代,图像质量参差不齐,对低质量图像进行高分辨率重建具有重要的研究与应用价值。基于 Transformer的单图像超分辨率方法通常将自注意力机制限制在局部非重叠窗口中,导致感受野受限、窗口边界失真以及高频细节重构能力不足等问题。为此,该文提出一种基于Swin IR的异质窗口注意力网络(Heterogeneous window Transformer Network for Image Super-Resolution, HWT-SRNet)。首先,设计异质窗口注意力机制,充分融合多尺度特征,以缓解窗口边界失真问题并有效扩大感受野。其次,针对Transformer在高频信息重构能力上的不足,提出一种高频先验特征提取网络,增强网络对边缘与纹理细节的恢复能力。实验结果表明,HWT-SRNet在Set5, Set14, BSD100, Urban100, Manga109五个基准测试集上,PSNR指标相比基线模型Swin IR提升0.10 dB至0.37 dB,同时,与其他具有代表性的超分模型CAT, ACT, ART等相比,在图像细节和纹理方面也取得了更优的视觉效果。
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关键词:
- 超分辨率重建 /
- Transformer /
- 异质窗口 /
- 高频先验
Abstract:In the era of big data, image quality varies greatly, making the reconstruction of high-resolution images from low-quality inputs a critical task in computer vision. Existing super-resolution methods based on window self-attention, such as SwinIR, encounter limitations in receptive field expansion and insufficient ability to capture high-frequency details. These shortcomings reduce their effectiveness in reconstructing fine image structures, thereby necessitating further improvements. To overcome these challenges, this study proposes the Heterogeneous Windows Transformer Network for Image Super-Resolution (HWT-SRNet), a novel architecture built upon SwinIR. By integrating innovative module designs, HWT-SRNet enhances the extraction of high-frequency details while simultaneously expanding the receptive field, offering a more advanced solution for super-resolution tasks. Methods Building upon the Swin IR framework, this study incorporates two key modules to optimize super-resolution reconstruction performance:(1) Heterogeneous Windows Transformer Block (HWTB): Traditional window-based self-attention mechanisms suffer from a constrained receptive field, limiting their ability to capture long-range dependencies. To overcome this limitation, HWTB alternates between square windows and pale windows, preserving local feature extraction while significantly expanding the receptive field. This alternating mechanism enables the network to better model both fine-grained details and global structural information, improving the overall image reconstruction quality. The choice of window size and alternation frequency is optimized to trade off between computational efficiency and feature extraction.(2) High-Frequency Prior Extraction Network (HFPEN): Transformer-based super-resolution models often struggle with capturing high-frequency details due to their inherent bias towards low-frequency components. To mitigate this issue, the HFPEN module is introduced to explicitly extract high-frequency prior information from images using a Gaussian Difference of Gaussian (DoG) filter. The DoG filter emphasizes high-frequency details, including edges and textures, by computing the difference between a lightly blurred image (containing mid-frequency information) and a more heavily blurred one (capturing low-frequency information).This high-frequency information is then fused with the heterogeneous window attention mechanism, allowing HWT-SRNet to enhance fine details while maintaining structural coherence. The DoG filter is applied in the spatial domain, enabling the model to effectively capture and reconstruct sharp edges and textures without the need for frequency-domain transformations. This approach ensures that the network can focus on high-frequency features while preserving the overall image structure. Results and Discussions To thoroughly assess the effectiveness of HWT-SRNet, we performed experiments on several widely used benchmark datasets, namely Set5, Set14, BSD100, Urban100, and Manga109. Our method was compared with representative state-of-the-art approaches, including ACT, ART, and CAT.,The results demonstrate its superior performance across key evaluation metrics (see Table 1 for detailed comparisons). Specifically, HWT-SRNet achieves improvements in PSNR ranging from 0.10 dB to 0.37 dB compared to baseline models, demonstrating its effectiveness in enhancing image quality. Additionally, structural similarity (SSIM) scores also exhibit consistent improvement, indicating better perceptual quality and more visually pleasing reconstructions. Qualitative results further confirm that HWT-SRNet is capable of restoring sharper edges, preserving textures, and reducing blurring artifacts compared to existing methods. To further validate the contribution of each component in HWT-SRNet, we conducted ablation studies to analyze the impact of the Heterogeneous Windows Transformer Block (HWTB) and the High-Frequency Prior Extraction Network (HFPEN) (seeTable 2 for ablation results).These advantages stem from the synergistic effect of heterogeneous window attention mechanisms and high-frequency prior extraction, which enable the network to effectively balance local feature refinement and global contextual understanding. By leveraging the alternating self-attention mechanisms and high-frequency prior extraction, HWT-SRNet provides a highly efficient solution for expanding the receptive field and improving high-frequency detail reconstruction.Conclusion Considering the limitations of existing super-resolution algorithms, this paper proposes a novel Heterogeneous Windows Transformer Network (HWT-SRNet), designed to improve image reconstruction quality by addressing challenges in receptive field expansion and high-frequency detail capture. The integration of heterogeneous window attention mechanisms and high-frequency prior feature extraction allows the model to achieve a more effective fusion of local and global features, leading to superior performance in both PSNR and SSIM. Experimental results confirm that HWT-SRNet surpasses existing state-of-the-art methods, providing a more efficient and accurate solution for super-resolution tasks. However, this study does not specifically explore the model's adaptability to noise interference in real-world scenarios. Future research can focus on further optimizing HWT-SRNet’s robustness to noisy and degraded inputs, improving its applicability to practical image restoration tasks in diverse environments. Additionally, the model's performance on specialized datasets, such as medical or satellite images, remains to be explored, which could further validate its generalization capabilities. -
表 1 不同方法各数据集的PSNR和SSIM均值比较
算法 缩放因子 Set5 Set14 BSD100 Urban100 Manga109 PSNR/SSIM/ PSNR/SSIM PSNR/SSIM PSNR/SSIM PSNR/SSIM ESWT[8] ×2 38.33/ 0.9615 34.22/ 0.9233 32.47/ 0.9034 33.27/ 0.9397 39.79/ 0.9790 CAT-R[7] 38.48/ 0.9625 34.53/ 0.9251 32.56/ 0.9045 34.08/ 0.9443 40.09/ 0.9804 Swin IR[6] 38.42/ 0.9623 34.46/ 0.9250 32.53/ 0.9041 33.81/ 0.9427 39.92/ 0.9797 ACT[14] 38.46/ 0.9626 34.60/ 0.9256 32.56/ 0.9048 34.07/ 0.9443 39.95/ 0.9804 CRAFT[18] 38.23/ 0.9615 33.92/ 0.9211 32.33/ 0.9016 32.86/ 0.9343 39.39/ 0.9786 ART[11] 38.56/ 0.9629 34.59/ 0.9267 32.58/ 0.9048 34.30/ 0.9452 40.24/ 0.9808 DFDN[20] 38.19/ 0.9612 33.85/ 0.9199 32.30/ 0.9013 32.68/ 0.9335 —— MDIESR[21] 38.17/ 0.9613 33.83/ 0.9200 32.31/ 0.9013 32.65/ 0.9331 -—— HWT-SRNet 38.59/ 0.9632 34.81/ 0.9287 32.58/ 0.9050 34.42/ 0.9453 40.25/ 0.9812 ESWT[8] ×3 34.63/ 0.9290 30.55/ 0.8464 29.23/ 0.8088 28.70/ 0.8628 34.05/ 0.9479 CAT-R[7] 34.99/ 0.9320 31.00/ 0.8539 29.49/ 0.8154 29.91/ 0.8848 35.29/ 0.9542 Swin IR[6] 34.97/ 0.9318 30.93/ 0.8534 29.46/ 0.8145 29.75/ 0.8826 35.12/ 0.9537 ACT[14] 35.03/ 0.9321 31.08/ 0.8541 29.51/ 0.8164 30.08/ 0.8858 35.27/0.954 CRAFT[18] 34.71/ 0.9295 30.61/ 0.8469 29.24/ 0.8093 28.77/ 0.8635 34.29/ 0.9491 ART[11] 35.07/ 0.9325 31.02/ 0.8541 29.51/ 0.8159 30.10/ 0.8871 35.39/ 0.9548 DFDN[20] 34.69/ 0.9293 30.55/ 0.8464 29.25/ 0.8089 28.70/ 0.8630 —— MDIESR[21] 34.69/ 0.9295 30.58/ 0.8465 29.25/ 0.8087 28.72/ 0.8634 —— HWT-SRNet 35.12/ 0.9344 31.06/ 0.8551 29.57/ 0.8173 30.18/ 0.8889 35.48/ 0.9552 ESWT[8] ×4 32.46/ 0.8979 28.80/ 0.7866 27.70/ 0.7410 26.56/ 0.8006 30.94/ 0.9136 CAT-R[7] 32.89/ 0.9044 29.13/ 0.7955 27.95/ 0.7500 27.62/ 0.8292 32.16/ 0.9269 Swin IR[6] 32.92/ 0.9044 29.09/ 0.7950 27.92/ 0.7489 27.45/ 0.8254 32.03/ 0.9260 ACT[14] 32.97/ 0.9031 29.18/ 0.7954 27.95/ 0.7507 27.74/ 0.8305 32.20/ 0.9267 CRAFT[18] 32.52/ 0.8989 28.85/ 0.7872 27.72/ 0.7418 26.56/ 0.7995 31.18/ 0.9168 ART[11] 33.04/ 0.9051 29.16/ 0.7958 27.97/ 0.7510 27.77/ 0.8321 32.31/ 0.9283 DFDN[20] 32.56/ 0.8989 28.87/ 0.7880 27.73/ 0.7414 26.59/ 0.8008 —— MDIESR[21] 32.49/ 0.8986 28.84/ 0.7867 27.73/ 0.7399 26.59/ 0.8007 —— HWT-SRNet 33.08/ 0.9060 29.23/ 0.7975 28.02/ 0.7520 27.82/ 0.8370 32.35/ 0.9296 表 2 不同方法各数据集的LPIPS均值比较(×4)
算法 Set5 Set14 BSD100 Urban100 Manga109 ESWT[8] 0.2078 0.2977 0.3383 0.2812 0.1912 CAT-R[7] 0.2061 0.2927 0.3279 0.2496 0.1819 Swin IR[6] 0.2079 0.2957 0.3321 0.2602 0.1847 ACT[14] 0.2078 0.2904 0.3235 0.2506 0.1840 CRAFT[18] 0.2136 0.3044 0.3389 0.2816 0.1920 ART[11] 0.2068 0.2913 0.3259 0.2464 0.1804 HWT-SRNet 0.2050 0.2907 0.3255 0.2448 0.1799 表 3 参数量与重构时间的比较
表 4 不同窗口大小对比实验结果
序号 窗口形状 窗口大小 Multi-adds(GMac) PSNR/SSIM 1 方形窗口 (8,8) 53.6 32.92/ 0.9044 (16,16) 63.8 32.98/ 0.9050 (32,32) 119.3 33.01/ 0.9051 2 栅栏形窗口 2 79.5 32.56/ 0.8989 4 82.4 32.82/ 0.9029 8 94.1 32.99/ 0.9049 16 120.3 33.01/ 0.9050 3 异质窗口 (8,8),8 81.4 33.00/ 0.9050 (8,8),16 87.5 33.01/ 0.9052 (16,16),4 73.1 32.90/ 0.9040 (16,16),8 87.0 33.03/ 0.9054 表 5 不同模块对比实验结果
序号 Swin IR 异质窗口 高频先验特征提取网络 PSNR/SSIM 1 √ × × 32.92/ 0.9044 2 √ √ × 33.03/ 0.9054 3 √ × √ 32.98/ 0.9049 4 √ √ √ 33.08/ 0.9060 -
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