【OpenCV3图像处理】线性滤波：均值滤波，高斯滤波

拟合圆

参考：
http://blog.csdn.net/liyuanbhu/article/details/50890587
http://blog.csdn.net/taily_duan/article/details/51907633

检测圆

参考：
http://blog.csdn.net/holybin/article/details/20214169
http://www.opencv.org.cn/forum.php?mod=viewthread&tid=34096
http://blog.csdn.net/thefutureisour/article/details/7599537