Development of a System for Pig Weight Measurement by Image Analysis

为了通过交接法估计猪的体重，我们制作了一个由摄像机和网状成像幻灯片投影仪组成的设备。分析从猪圈里的猪的图像开始，当将幻灯片投影仪放置在水面上方的天花板上，从上方投射出猪圈上的格纹阴影线，并将摄像机固定在投影仪旁边拍摄猪的图像。从猪的图像中，测量了展台肩膀和地板之间边界处阴影线的像素间隙，并与高度相关。并测量了猪的指定投影图像区域，该区域缺少耳朵和尾巴的图像区域。然后用面积和高度的指数函数估计猪的体重，并与实测值进行比较。对12头猪舍产仔，在81日龄至98日龄期间分5次进行猪体重估算试验。安装在天花板上的装置提供了猪以正常姿势站立喝水的清晰图像。估计每头猪体重的平均相对误差为2.1%，标准差为1.8%。该装置对猪群体重有较好的预测效果，但对猪群体重的预测误差不存在波动。估计组平均体重与测量组平均体重之间的差异仅为+0.3 kg，相对误差为0.8%。尽管在积极方面高估了，但它表明了实际的准确性。尽管估计猪体重的可靠性仍然存在限制，但该方法可以快速估计体重

To estimate pig weight by a hand-off method, we made a device composed of a video camera and a mesh imaged slide projector.Analysis proceeded from the image of a pig in a pen, when projecting shadow lines of lattice pattern on the pig from above with the slide projector placed at the ceiling above the waterer and taking image of the pig with the video camera fixed beside the projector. From the image of the pig, the gap in pixel of a shadow line at the border between the shoulder and the floor of the booth was measured and related with height. The specified projected image area of the pig, which lacked the image area of ears and a tail, was also measured. Then pig weight was estimated from an exponential function of the area and the height and was compared with the measured one. For the litter of 12 growing pigs in the pen, experiments to estimate pig weight were done at five times during an age of 81 days to that of 98 days. The device set at the ceiling provided a clear image of a pig standing in a normal posture while drinking water.A mean relative error of 2.1% with 1.8% in standard deviation was obtained when estimate each pig weight. The fluctuation of error to estimate pig weight was remained, however, the device had a good prediction for the group weight of the pigs. The difference between estimated and measured mean group weights was only +0.3 kg, or 0.8% in relative error. Despite overestimating in positive side, it indicates a practical accuracy. Although a limitation in reliability to estimate pig weight remains, the method allows for rapid estimation of the weight