Set options to step in range

hi, there is an option to set an array for choose options for the step in the range?

i try to create a slider for the user to change the size of images which are inside col’s,
so i try to set the cols size from the slider… what i have below is work, but i have two problems in it:

  1. my step range not works (it still step:1), so the user should try find himself to reach the exact col value to actually change the col (its impossible to be like this)
  2. and the change of the col comes only with click and not “live” with the change as i want it to be.

html:

controller:
//not work : $scope.step = [20,25,33,50,67,75,80]

$scope.imgColSize= {
min:“20”,
max:“80”,
value:“50”
}

$scope.changeValue = function() {
$scope.cola = "col-" + $scope.imgColSize.value;
}

}