全局画布配置
canvasOptions
canvasOptions其实就是canvas的一套模板。在canvasOptions中配置好canvas的通用属性，那么在canvas中只需要将与canvasOptions中不同的属性再做个设值即可，避免了相同属性重复定义的麻烦。
下面是canvasOptions相关属性的介绍：
{
"canvasOptions": {
"graphBackgroundFill": {
"fillAlpha": 1,
"fillColor": "#000000"
},
"graphBorderStyle": {
"lineWidth": 1,
"lineColor": "#000000",
"lineAlpha": 1,
"lineCap": "BUTT",
"lineJoin": "MITER",
"dashStyle": {
"intervals": [0, 0, 0, 0],
"phase": 0
}
},
"plotBackgroundFill": {
"fillAlpha": 1,
"fillColor": "#000000"
},
"plotBorderStyle": {
"lineWidth": 1,
"lineColor": "#000000",
"lineAlpha": 1,
"lineCap": "BUTT",
"lineJoin": "MITER",
"dashStyle": {
"intervals": [0, 0, 0, 0],
"phase": 0
}
},
"chartPadding": {
"left": 0,
"top": 0,
"right": 0,
"bottom": 0
},
"graphPadding": {
"left": 0,
"top": 0,
"right": 0,
"bottom": 0
}
}
}
chartOptions中各部分的含义请见canvas