Source file hash.ml

type t = Int64.t

module Set = Set.Make (Int64)

let bit_set number n b =
  let open Int64 in
  if b then logor number (shift_left one n)
  else logand number (lognot (shift_left one n))

let bit_check number n =
  Int64.(compare (logand (shift_right number n) one) one) = 0

(* Get average pixel value *)
let pixel_avg px =
  Pixel.fold (fun a b -> a +. b) px 0.0 /. float_of_int (Pixel.length px)

let phash im =
  let im =
    Filter.eval_expr (Expr.resize 8 8) ~width:8 ~height:8 im.Image.ty im.color
      [| Image.any im |]
  in
  let h = ref Int64.zero in
  let index = ref 0 in
  for j = 0 to 7 do
    for i = 0 to 7 do
      let p = Image.get_pixel im i j |> pixel_avg in
      h := bit_set !h !index (p > 0.5);
      incr index
    done
  done;
  !h

let diff a b =
  let diff = ref 0 in
  for i = 0 to 63 do
    if bit_check a i <> bit_check b i then incr diff
  done;
  !diff

let equal a b = diff a b = 0
let to_string hash = Printf.sprintf "%016Lx" hash
let to_int64 hash = hash