Google Earth Engine（GEE）——数组转影像和降维以及矩阵的相乘变换
函数：
toArray()
Converts an image collection into an image of 2D arrays. At each pixel, the images that have valid (unmasked) values in all bands are laid out along the first axis of the array in the order they appear in the image collection. The bands of each image are laid out along the second axis of the array, in the order the bands appear in that image. The array element type will be the union of the types of each band.
将一个图像集合转换为一个二维数组的图像。在每个像素点上，在所有波段中具有有效（未屏蔽）值的图像，按照它们在图像集合中出现的顺序，沿着阵列的第一轴排列。每幅图像的波段沿数组的第二轴排列，以波段在该图像中出现的顺序排列。数组元素的类型将是每个波段的类型的结合。
Arguments:
this:collection (ImageCollection):
Image collection to convert to an array image. Bands must have scalar values, not array values.要转换为数组图像的图像集合。波段必须有标量值，而不是数组值。