基于群体协同优化的高清图像前景遮罩提取算法

高清图像(高分辨率图像)前景遮罩提取问题是图像合成、自动前景提取等图像处理领域的热点难题,其本质是前景背景像素对的大规模组合优化问题,目前相关研究成果较少.本文针对问题维度过高难以直接求解这一问题,设计了基于RGB聚类的多类协同优化策略,以实现决策空间的有效降维;给出协同目标反馈的分组优化策略,通过将协同目标中的最优前景背景像素对作为启发式信息反馈给每个分组,实现大规模组合优化问题的分组协同求解.在分组优化策略的基础上,论文提出了基于分组协同的群体竞争优化算法(competitive swarm optimization algorithm based on group collaboration,GC-CSO),为高维优化问题分析提供了借鉴.为了验证所提方法的有效性,本文选用alpha matting基准数据集作为测试数据,通过与群体竞争优化算法、典型带分组策略的大规模优化算法进行对比分析,验证了:(1)基于RGB聚类的协同优化策略可以显著地降低问题维度;(2) GC-CSO算法提高了高清图像前景遮罩的提取精度.

APFD:an effective approach to taxi route recommendation with mobile trajectory big data

With the rapid development of data-driven intelligent transportation systems,an efficient route recommendation method for taxis has become a hot topic in smart cities.We present an effective taxi route recommendation approach(called APFD)based on the artificial potential field(APF)method and Dijkstra method with mobile trajectory big data.Specifically,to improve the efficiency of route recommendation,we propose a region extraction method that searches for a region including the optimal route through the origin and destination coordinates.Then,based on the APF method,we put forward an effective approach for removing redundant nodes.Finally,we employ the Dijkstra method to determine the optimal route recommendation.In particular,the APFD approach is applied to a simulation map and the real-world road network on the Fourth Ring Road in Beijing.On the map,we randomly select 20 pairs of origin and destination coordinates and use APFD with the ant colony(AC)algorithm,greedy algorithm(A*),APF,rapid-exploration random tree(RRT),non-dominated sorting genetic algorithm-II(NSGA-II),particle swarm optimization(PSO),and Dijkstra for the shortest route recommendation.Compared with AC,A*,APF,RRT,NSGA-II,and PSO,concerning shortest route planning,APFD improves route planning capability by 1.45%–39.56%,4.64%–54.75%,8.59%–37.25%,5.06%–45.34%,0.94%–20.40%,and 2.43%–38.31%,respectively.Compared with Dijkstra,the performance of APFD is improved by 1.03–27.75 times in terms of the execution efficiency.In addition,in the real-world road network,on the Fourth Ring Road in Beijing,the ability of APFD to recommend the shortest route is better than those of AC,A*,APF,RRT,NSGA-II,and PSO,and the execution efficiency of APFD is higher than that of the Dijkstra method.