Integration of category-quantity adaptive deep data augmentation and transfer learning for reef-building coral recognition
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摘要: 造礁珊瑚识别对于珊瑚礁生态系统的保护与监测具有重要意义。深度学习作为图像识别的前沿技术,在珊瑚识别领域逐渐得到应用。然而,其识别性能仍然面临挑战。其中,数据集中类别间样本数量不平衡和数据多样性欠缺是两个主要问题。前者使得深度学习模型在特征提取过程中更偏向于样本数较多的类,对少数类(尤其是濒危珊瑚)的学习能力不足进而影响其识别准确度。后者因为数据缺乏多样性使得模型无法充分学习各种珊瑚特征,进而限制了特征提取的能力。鉴于此,本文提出了一种融合类别数量自适应深度数据增强和迁移学习的造礁珊瑚类型识别方法。针对第一个问题,本文利用识别结果评价指标F1-score定义的数据生成量化公式对原始深度数据增强方法DeepSMOTE进行改进,提出了类别数量自适应的深度数据增强方法DeepSMOTE-F1。该方法根据每类珊瑚的识别结果自适应地增强其样本数量,确保模型充分学习各类珊瑚特征。针对第二个问题,利用迁移学习强化了模型的提取能力。实验结果表明,在RSMAS、EILAT和EILAT2这3个代表性珊瑚识别数据集上,相较于原始DeepSMOTE,本文提出的DeepSMOTE-F1识别准确率分别提升了2.88%、0.39%和1.54%;与现有的珊瑚智能识别方法相比,准确率分别提升了0.76%、1.40%和1.30%。Abstract: Recognition of reef-building corals is important for protecting and monitoring coral reef ecosystems. Deep learning, as an advanced technology in image recognition, has been increasingly applied in coral recognition. However, its performance is still challenged by several issues, such as the imbalance of samples among different coral categories within a dataset and the limitation of data diversity. The former makes the deep learning model more likely to extract features from classes with a large number of samples and, therefore, decreases its ability to recognize small-sample-size corals, which often refer to endangered ones needing to be protected. The latter further reduces the performance of deep learning in recognizing corals with different appearances and are captured in variant environments. To solve these two problems, this study develops a reef-building coral recognition method by integrating a category-quantity adaptive deep data augmentation algorithm and transfer learning. To address the first problem, a category-quantity adaptive deep data augmentation algorithm named DeepSMOTE-F1 is proposed. This algorithm improves the existing DeepSMOTE by introducing a sample-size determination stagey using an F1-score based evaluation metric. It can adaptively augment the number of samples of each category of corals according to its recognition performance so that the deep learning model can fully learn features from each class of corals. For the second problem, transfer learning is used to further enhance the model's ability to extract features. The experimental results on three widely used public coral recognition datasets, RSMAS, EILAT, and EILAT2 show that the recognition accuracy of the proposed DeepSMOTE-F1 is improved by 2.88%, 0.39%, and 1.54%, respectively, compared with the traditional DeepSMOTE; and the accuracy of the integrated method is improved by 0.76%, 1.40% and 1.30% compared with the existing deep learning methods for coral recognition.
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Key words:
- coral recognition /
- deep learning /
- imbalanced dataset /
- data augmentation /
- transfer learning.
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图 3 DeepSMOTE深度数据增强结果示例:a中展示了RSMAS数据集[20]中3个珊瑚类:Colpophyllia natans, Acropora cervicornis和Meandrina meandrites,b中展示了EILAT数据集[20]中3个珊瑚类:Branches TypeⅡ, Brain Coral和Favid Coral。每个类有3个示例,从左到右依次为原始图像、近邻图像、新图像。右上角的数值是由SMOTE算法随机确定的比例因子,介于0~1,表示新的图像与原始图像和近邻图像的接近程度。值越大则代表越接近原始图像,值越小则代表越接近近邻图像
Fig. 3 The example results of deep data augmentation using DeepSMOTE: a. displays three classes of coral in the RSMAS dataset[20]: Colpophyllia Natans, Acropora Cervicornis and Meandrina Meandrites, b. displays three classes of coral in the EILAT dataset[20]: Branches TypeⅡ, Brain Coral和Favid Coral. There are three examples provided for each class. The 1st−3rd column shows the original image, the nearest neighbor image, and the generated image, respectively. The value in the top right corner is the scale factor randomly determined by the SMOTE, which ranges from 0 to 1. It indicates the degree of similarity between the generated image and the original image, as well as the nearest neighbor image. A higher value indicates greater similarity with the original image, while a lower value indicates greater similarity with the nearest neighbor image
表 1 RSMAS数据集基本信息[12]
Tab. 1 The information of the RSMAS dataset
数据集 类 数量 RSMAS Acropora cervicornis 109 Acropora palmata 77 Colpophyllia natans 57 Diadema antillarum 63 Diploria strigosa 24 Gorgonians 60 Millepora alcicornis 22 Montastraea cavernosa 79 Meandrina meandrites 54 Montipora spp. 28 Palythoas palythoa 32 Sponge fungus 88 Siderastrea siderea 37 Tunicates 36 总数 766 表 2 EILAT数据集基本信息[12]
Tab. 2 The basic information of the EILAT dataset
数据集 类 数量 EILAT Sand 87 Urchin 80 Dead Coral 280 Brain Coral 160 Favid Coral 200 Branches TypeⅠ 23 Branches TypeⅡ 216 Branches TypeⅢ 77 总数 1123 表 3 EILAT2数据集基本信息[24]
Tab. 3 The basic information of the EILAT2 dataset
数据集 类 数量 EILAT2 Sand 80 Urchin 14 Brain Coral 71 Favid Coral 89 Branches Type 49 总数 303 表 4 参数设置
Tab. 4 The setting of parameters
模型 批次大小 学习率 迭代次数 ResNet-50 32 0.001/ 0.0001 /0.00001 300/500/ 1000 64 0.001/ 0.0001 /0.00001 300/500/ 1000 128 0.001/ 0.0001 /0.00001 300/500/ 1000 表 5 每个敏感性实验在RSMAS、EILAT和EILAT2数据集上的识别准确率
Tab. 5 The classification accuracy of each sensitivity experiment on RSMAS, EILAT, and EILAT2 datasets
方法 RSMAS EILAT EILAT2 基线 84.19% 74.28% 74.23% DeepSMOTE 85.00% 79.22% 80.08% DeepSMOTE-F1 87.88% 79.61% 81.62% 迁移学习 97.54% 94.84% 97.06% DeepSMOTE-F1 + 迁移学习 98.81% 98.02% 99.01% 表 6 本文方法提供最佳识别准确率的参数设置
Tab. 6 The setting of parameters of the proposed method on achieving the highest classification accuracy
数据集 批次大小 学习率 迭代次数 RSMAS 64 0.001 500 EILAT 32 0.001 300 EILAT2 32 0.001 300 表 7 与现有珊瑚识别方法在RSMAS、EILAT和EILAT2数据集上的识别准确率对比
Tab. 7 The comparison of classification accuracy with existing coral classification methods on RSMAS, EILAT and EILAT2 datasets
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