let mutable median_bg = (!max).[0] - ((!max).[0] - (!min).[0]) / 4.0
let mutable median_fg = (!min).[0] + ((!max).[0] - (!min).[0]) / 4.0
let mutable d_bg = new Image<Gray, float32>(img.Size)
let mutable d_fg = new Image<Gray, float32>(img.Size)
let mutable fg = new Image<Gray, byte>(img.Size)
let mutable median_bg = (!max).[0] - ((!max).[0] - (!min).[0]) / 4.0
let mutable median_fg = (!min).[0] + ((!max).[0] - (!min).[0]) / 4.0
let mutable d_bg = new Image<Gray, float32>(img.Size)
let mutable d_fg = new Image<Gray, float32>(img.Size)
let mutable fg = new Image<Gray, byte>(img.Size)