echarts关系图圆心颜色渐变

let option = {
    backgroundColor: '#1a4377',
    animationDurationUpdate: 1500,                       // 动画更新变化时间
    animationEasingUpdate: 'quinticInOut',               // 动画缓动效果
    series: [
        {
            type: 'graph',                               // 选择关系图
            layout: 'force',                             // 'none'无部局，需要自己添加坐标,'circular'环形布局,'force'引导布局，出来的效果随机
            force:{
                repulsion: 1000,                         // 节点间的斥力
                edgeLength: 50                           // 两节点间距离，受斥力影响
            },
            roam: true,
            label: {                                     // 节点中字的全局样式
                normal: {
                    show: true,
                    color: '#fff'
                }
            },
            itemStyle: {                                 // 节点圆圈的全局样式
                normal: {
                    // borderColor: '#fff',
                    // borderWidth: 1,
                    // shadowBlur: 1,
                    // shadowColor: 'rgba(0, 0, 0, 0.3)'
                }
            },
            focusNodeAdjacency: true,                    // 鼠标悬浮一个节点时突出与它有关系的节点，淡化其它无关系的节点
            data: [                                      // 各个节点数据
                {
                    id: 'a1',
                    name: '校园大数据',
                    symbolSize: 120,                     // 决定各个节点大小
                    draggable: true,                     // 可拖拽
                    category: 0,                         // 节点间分类
                    itemStyle: {                         // 各圆圈自定义样式
                        normal: {
                            borderColor: '#b457ff',
                            borderWidth: 1,
                            shadowBlur: 20,
                            shadowColor: '#b457ff',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [          // 由中心向四周渐变
                                {
                                    offset: 0,
                                    color: "rgba(180, 87, 255, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(180, 87, 255, 1)"
                                }
                            ]),
                        }
                    }
                },
                {
                    id: '2',
                    name: '舆情大数据',
                    symbolSize: 100,
                    itemStyle: {
                        normal: {
                            borderColor: '#04f2a7',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#04f2a7',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(4, 242, 164, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(4, 242, 164, 1)"
                                }
                            ]),
                        }
                    },
                    category: 1,
                },
                {
                    id: '3',
                    name: '用户分析',
                    symbolSize: 80,
                    category: 1,
                    itemStyle: {
                        normal: {
                            borderColor: '#04f2a7',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#04f2a7',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(4, 242, 164, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(4, 242, 164, 1)"
                                }
                            ]),
                        }
                    },
                },
                {
                    id: '4',
                    name: '话题分析',
                    symbolSize: 80,
                    category: 1,
                    itemStyle: {
                        normal: {
                            borderColor: '#04f2a7',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#04f2a7',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(4, 242, 164, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(4, 242, 164, 1)"
                                }
                            ]),
                        }
                    },

                },
                {
                    id: '5',
                    name: '评论分析',
                    symbolSize: 80,
                    category: 1,
                    itemStyle: {
                        normal: {
                            borderColor: '#04f2a7',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#04f2a7',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(4, 242, 164, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(4, 242, 164, 1)"
                                }
                            ]),
                        }
                    },

                },
                {
                    id: '6',
                    name: '图书馆分析',
                    symbolSize:100,
                    category: 2,
                    itemStyle: {
                        normal: {
                            borderColor: '#82dffe',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#82dffe',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(130, 223, 254, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(130, 223, 254, 1)"
                                }
                            ]),
                        }
                    },

                },
                {
                    id: '7',
                    name: '借阅分析',
                    symbolSize:80,
                    category: 2,
                    itemStyle: {
                        normal: {
                            borderColor: '#82dffe',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#82dffe',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(130, 223, 254, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(130, 223, 254, 1)"
                                }
                            ]),
                        }
                    },

                },
                {
                    id: '8',
                    name: '借阅排行',
                    symbolSize:80,
                    itemStyle: {
                        normal: {
                            borderColor: '#82dffe',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#82dffe',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(130, 223, 254, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(130, 223, 254, 1)"
                                }
                            ]),
                        }
                    },
                    category: 2,

                },
                {
                    id: '9',
                    name: '图书收录',
                    symbolSize:80,
                    itemStyle: {
                        normal: {
                            borderColor: '#82dffe',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#82dffe',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(130, 223, 254, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(130, 223, 254, 1)"
                                }
                            ]),
                        }
                    },
                    category: 2,

                },
                {
                    id: '10',
                    name: '图书分析',
                    symbolSize:80,
                    category: 2,
                    itemStyle: {
                        normal: {
                            borderColor: '#82dffe',
                            borderWidth: 1,
                            shadowBlur: 10,
                            shadowColor: '#82dffe',
                            color: new echarts.graphic.RadialGradient(0.5, 0.5, 1.0, [
                                {
                                    offset: 0,
                                    color: "rgba(130, 223, 254, 0.1)"
                                },
                                {
                                    offset: 1,
                                    color: "rgba(130, 223, 254, 1)"
                                }
                            ]),
                        }
                    },

                }],
            links: [                                // 各个节点间的关系，可传id或name,这里选择的id
                {
                    source: 'a1',
                    target: '2'
                },
                {
                    source: '2',
                    target: '3',
                },
                {
                    source: '2',
                    target: '4',
                },
                {
                    source: '2',
                    target: '5',
                },
                {
                    source: 'a1',
                    target: '6',
                },
                {
                    source: '6',
                    target: '10',
                },
                {
                    source: '6',
                    target: '7',
                },
                {
                    source: '6',
                    target: '8',
                },
                {
                    source: '6',
                    target: '9'
                }
            ],
            lineStyle: {                      // 连线的样式
                normal: {
                    opacity: 0.9,
                    width: 1,    
                    curveness: 0              // 线的弯曲程度，0代表直线，数值越大越弯
                }
            }
        }
    ]
};

let myChart = echarts.init(document.getElementById('relate'));
myChart.setOption(option);