def getSobels
      unless defined?(@sobels)
        l = []
        (0...(@width * @height)).each do |xy|
          s = getSobel(xy % @width, (xy / @width).floor)
          l.push(s)
        end
        @sobels = l
      end
      @sobels
    end
def getSobels
      unless defined?(@sobels)
        l = []
        (0...(@width * @height)).each do |xy|
          s = getSobel(xy % @width, (xy / @width).floor)
          l.push(s)
        end
        @sobels = l
      end
      @sobels
    end
Retrieve the Sobel values for every pixel and set it as @sobel.