传统轻量级图像语义分割网络中的跨步下采样卷积导致感受野呈现刺状分布，使得像素点利用率出现系统偏差，影响分割精度的提升。为此，针对传统的轻量级图像语义分割网络设计一种奇偶交叉卷积的下采样模块，在跨步奇数卷积模块前增加单步偶数卷积模块，在一定程度上缓解了刺状分布带来的不良影响，消除了分割网络中不同空间位置上像素利用率的偏差，最终提高了模型对像素点的分割精度。通过7种不同轻量级图像语义分割网络的对比可以看出，所提模型可以明显消除刺状分布，使分割网络的精度进一步提高，同时也证明了该模型适用于不同的轻量级网络，具有普适性。
The multi-step down-sampling convolution in traditional lightweight image semantic segmentation networks easily causes a thorn-like distribution in receptive fields. This will introduce systematic deviations in pixel utilization and finally affect the improvement of segmentation accuracy. Regarding this problem, a down-sampling module of parity cross convolution is designed for traditional lightweight image semantic segmentation networks. In the scheme, an even-convolution module is added before the strided odd-numbered convolution module, in order to alleviate the negative effects caused by spur distribution. Accordingly, the deviation of pixel utilization at different spatial positions in the segmentation network can be eliminated effectively, and the improvement of pixel segmentation accuracy can be finally achieved. Experimental results demonstrate that through the comparison of seven different lightweight image semantic segmentation networks, the proposed model can obviously eliminate the thorn-like distribution and improve the accuracy of the segmentation network. Also, the proposed model performs excellent adaptability to different lightweight networks.
[1] 李欣,唐文莉,杨博.利用深度残差网络的高分遥感影像语义分割[J].应用科学学报, 2019, 37(2):282-290. Li X, Tang W L, Yang B. Semantic segmentation of high-resolution remote sensing image based on deep residual network[J]. Journal of Applied Sciences, 2019, 37(2):282-290.(in Chinese)
[2] Luo W, Li Y, Urtasun R, et al. Understanding the effective receptive field in deep convolutional neural networks[C]//Proceedings of the 30th International Conference on Neural Information Processing Systems, 2016:4905-4913.
[3] Chen L C, Papandreou G, Kokkinos I, et al. Deeplab:semantic image segmentation with deep convolutional nets, atrous convolution, and fully connected CRFs[J]. IEEE Transactions on Pattern Analysis and Machine Intelligence, 2017, 40(4):834-848.
[4] Wang P, Chen P, Yuan Y, et al. Understanding convolution for semantic segmentation[C]//2018 IEEE Winter Conference on Applications of Computer Vision (WACV). IEEE, 2018:1451-1460.
[5] Howard A, Sandler M, Chu G, et al. Searching for mobilenetv3[C]//Proceedings of the IEEE International Conference on Computer Vision, 2019:1314-1324.
[6] Yu C, Wang J, Peng C, et al. Bisenet:bilateral segmentation network for real-time semantic segmentation[C]//Proceedings of the European Conference on Computer Vision (ECCV), 2018:325-341.
[7] 李宝奇,贺昱曜,何灵蛟,等.基于全卷积神经网络的非对称并行语义分割模型[J].电子学报, 2019, 47(5):1058-1064. Li B Q, He Y Y, He L J, et al. Asymmetric parallel semantic segmentation model based on full convolutional neural network[J]. Acta Electronica Sinica, 2019, 47(5):1058-1064.(in Chinese)
[8] 韩慧慧,李帷韬,王建平,等.编码-解码结构的语义分割[J].中国图象图形学报, 2020, 25(2):255-266. Han H H, Li W T, Wang J P, et al. Semantic segmentation of encoder-decoder structure[J]. Journal of Image and Graphics, 2020, 25(2):255-266.(in Chinese)
[9] Poudel R P K, Liwicki S, Cipolla R. Fast-SCNN:fast semantic segmentation network[DB/OL]. 2019[2019-02-12]. https://arxiv.org/abs/1902.04502.
[10] Yu C, Gao C, Wang J, et al. BiSeNet V2:bilateral network with guided aggregation for realtime semantic segmentation[DB/OL]. 2020[2020-04-05]. https://arxiv.org/abs/2004.02147.
[11] Poudel R P K, Bonde U, Liwicki S, et al. Contextnet:exploring context and detail for semantic segmentation in real-time[DB/OL]. 2018[2018-11-05]. https://arxiv.org/abs/1805.04554.
[12] Li G, Yun I, Kim J, et al. DABNet:depth-wise asymmetric bottleneck for real-time semantic segmentation[DB/OL]. 2019[2019-10-01]. https://arxiv.org/abs/1907.11357.
[13] Li X, Zhou Y, Pan Z, et al. Partial order pruning:for best speed/accuracy trade-off in neural architecture search[C]//Proceedings of IEEE Conference on Computer Vision and Pattern Recognition, 2019:9145-9153.
[14] Liu M, Yin H. Feature pyramid encoding network for real-time semantic segmentation[DB/OL]. 2019[2019-09-18]. https://arxiv.org/abs/1909.08599.
