本教程的主要目的是实现点线面矢量对栅格的转换，这里我们首先要看一下这个属性信息中是有一个X的列表，这也是转换前所需要的一个必备参数，当你在使用其它矢量进行转换的过程要完成此类转换的主要目的就是获取矢量属性值，从而给不同的栅格进行赋值。
ee.Reducer.first()
Returns a Reducer that returns the first of its inputs.
No arguments.
Returns: Reducer
reduceToImage(properties, reducer)
Creates an image from a feature collection by applying a reducer over the selected properties of all the features that intersect each pixel.
Arguments:
this:collection (FeatureCollection):
Feature collection to intersect with each output pixe