Calculate how many pixels=1 in a 3*3 kernel based on GEE

Question

Now, I have a cropland map. It's only one band, 1=cropland,0=Non-cropland. So how to calculate how many pixels=1 in a 3*3 kernel? and then get a map of contain the numbers.

eg:

[1,0,1],  
[1,0,1],  
[1,1,0] 

stand for 9 pixels. how to get the number of '1' =6?

Answer 1

Probably just sum it. If you sum of 3x3 kernel, you will have how many ones you have.