蔡骋, 宋肖肖, 何进荣. 基于计算机视觉的牛脸轮廓提取算法及实现[J]. 农业工程学报, 2017, 33(11): 171-177. DOI: 10.11975/j.issn.1002-6819.2017.11.022
    引用本文: 蔡骋, 宋肖肖, 何进荣. 基于计算机视觉的牛脸轮廓提取算法及实现[J]. 农业工程学报, 2017, 33(11): 171-177. DOI: 10.11975/j.issn.1002-6819.2017.11.022
    Cai Cheng, Song Xiaoxiao, He Jinrong. Algorithm and realization for cattle face contour extraction based on computer vision[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(11): 171-177. DOI: 10.11975/j.issn.1002-6819.2017.11.022
    Citation: Cai Cheng, Song Xiaoxiao, He Jinrong. Algorithm and realization for cattle face contour extraction based on computer vision[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(11): 171-177. DOI: 10.11975/j.issn.1002-6819.2017.11.022

    基于计算机视觉的牛脸轮廓提取算法及实现

    Algorithm and realization for cattle face contour extraction based on computer vision

    • 摘要: 计算机视觉技术已越来越多地应用于检测牛个体行为以给出养殖管理决策,牛脸轮廓的提取及形状分析能够进一步提高牛身份鉴别,咀嚼分析及健康状况评估的自动化程度。为实现基于计算机视觉的无接触、高精度、适用性强的肉牛养殖场环境下的牛脸轮廓提取,提出用自适应级联检测器定位牛脸位置,用统计迭代模型提取牛脸轮廓的方法。该方法采集牛脸正面图像,用级联式检测器定位出牛脸的位置,并分别采用监督式梯度下降算法(supervised descent method, SDM),局部二值算法(local binary features, LBF)和主动外观模型算法(fast active appearance model, FAAM)3种算法被用于提取牛脸轮廓。对20头肉牛共拍摄800幅牛脸正面图,随机选取训练数据720幅和测试数据80幅。结果表明,主动外观模型算法准确率最高,其轮廓提取误差为0.0184 像素,适于应用在轮廓提取精度要求较高的场合,而局部二值算法的运行效率最高,在分辨率为744 像素(水平)?852像素(垂直)的牛脸图像中轮廓提取时间为0.35 s,更适于应用在实时性要求较高的场合。该方法可实现养殖场中肉牛的无接触精确的面部轮廓提取,具有适用性强、成本低的特点。

       

      Abstract: Abstract: Since cattle facial information is very rich, ranging from skin color, chewing conditions to health status, it is of great importance for cattle disease monitoring. This paper proposed a scheme on cattle facial automatic extraction to cope with the problems caused by different camera angles, varied illumination and partial occlusion. Three classical human facial contour extraction algorithms were employed in the study: Supervised descent method (SDM), local binary features (LBF) and fast active appearance model (FAAM). For contour extraction performance evaluation, 800 cattle facial images were collected from a cattle farm at Northwest A&F University. For each cattle face, 29 facial feature points were manually labeled. In order to cope with cattle face scale and rotation, all the labeled facial feature points were aligned to a normalized model. Compared with human face, cattle face height-width ratio was much larger. Based on the characteristics of cattle face, this study used the AdaBoost detector to train cattle face detector. Because cattle face was rather long, we cut the image to the size of 15×25 pixels. And the background was a negative sample with the same size. The detection rate of the cattle face detector for 800 cattle face images was 96%. Considering the characteristics of cattle face, we improved the algorithms and optimized our parameters. Also because of the long face, a split model was used to initialize the cattle face model. The first part included an eye contour with cheeks on both sides, and the second part included the nose and mouth contour. The results showed that the accuracy of the contour extraction was improved significantly. We then analyzed and compared the time efficiency and the accuracy of the 3 algorithms. Finally, the performance of each method was evaluated by the Euclidean errors normalized by the left and right corners of the eyes and their corresponding computational time costs. The average computational costs of the 3 contour information extraction methods were 1.75, 0.35, and 60.62 s respectively. The average pairwise Euclidean errors normalized by the left and right corners of the eyes were 0.0188, 0.0245, and 0.0184 pixel. The experiment verified the feasibility and practicability of the facial contour extraction methods. Results showed that the FAAM algorithm achieved the highest accuracy with the minimal alignment errors while the LBF algorithm was the most efficient. Therefore, in the process of facial contour extraction, we can choose proper algorithm in varied situation which requires different accuracy and efficiency. The contour extraction algorithm can effectively extract cattle facial contour information, which provides a theoretical basis for the further analysis of cattle facial expressions. As this is the first time that the contour extraction algorithm is applied to cattle face analysis, the present study serves as a good guide for other researches, which provides feasible data for computer vision based cattle disease analysis and a comprehensive guideline on cattle facial analysis under different circumstances in intelligent farm.

       

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