函数：
size()
Returns the number of elements in the collection.
返回集合中元素的数量。
Arguments:
this:collection (FeatureCollection):
The collection to count.
Returns: Integer
融合影像可以一个接一个进行融合
merge(collection2)
Merges two image collections into one. The result has all the images that were in either collection.将两个图片集合并为一个。其结果是所有的图像都在任何一个集合中。
Arguments:
this:collection1 (ImageCollection):
The first collection to merge.
collection2 (ImageCollection):
The second collection to merge.
Returns: ImageCollection
标签：Engine,1986,Google,ImageCollection,collection,merge,Returns,Arguments,collection From： https://blog.csdn.net/qq_31988139/article/details/121195776