annotation.rb

a = { 
  "annotations" => [
    {
      "x" => 19,
      "y" => 20,
      "w" => 50,
      "h" => 50,
      "predictions" => {
        "green" => 0.2,
        "red" => 0.95
      }
    }
   ]}

def hstorify_annotation(annotation)
 annotation.inject({}) do |acc, (k,v)|
    acc[k] = v if ["x", "y", "w", "h"].include?(k)
    if k == "predictions"
      v.each do |(pred_k, pred_v)|
        acc[pred_k + "_prediction"] = pred_v
      end
    end
    acc
 end
end

annotations = a["annotations"].collect{|a| hstorify_annotation(a)}

pp annotations

# =>
[{"x"=>19,
  "y"=>20,
  "w"=>50,
  "h"=>50,
  "green_prediction"=>0.2,
  "red_prediction"=>0.95}]