Closest will search for the parent elements. Here the input is not the parent element of the image. Its a sibling only. You can use siblings() selector for this purpose.
var input = $(image).siblings("input");
Or you can use,
var input = $(image).closest(".col-md-2").find("input");
- Get the parent div(since the image and input are under same parent)
- Then find the child input of that parent
solved jQuery Find Closest Input