今天简单介绍一些核函数：ee.Kernel
在GEE当中有很多关于核函数的函数，所以我们大致看一下，其实大多情况下都是对核的参数设定
ee.Kernel.chebyshev(radius, units, normalize, magnitude)
ee.Kernel.circle(radius, units, normalize, magnitude)
ee.Kernel.compass(magnitude, normalize)
ee.Kernel.cross(radius, units, normalize, magnitude)
ee.Kernel.diamond(radius, units, normalize, magnitude)
ee.Kernel.euclidean(radius, units, normalize, magnitude)
ee.Kernel.fixed(width, height, weights, x, y, normalize)
ee.Kernel.gaussian(radius, sigma, units, normalize, magnitude)
ee.Kernel.kirsch(magnitude, normalize