Source file ocolor_color_space.ml
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open Ocolor_types
type srgb = Srgb of float * float * float
type xyz = XYZ of float * float * float
type lab = Lab of float * float * float
let (d65 : xyz) = XYZ(0.95047, 1.0000, 1.08883)
let srgb_of_rgb (r, g, b: rgb) : srgb =
Srgb (float_of_int r /. 255., float_of_int g /. 255., float_of_int b /. 255.)
let xyz_of_srgb (Srgb(r, g, b) : srgb) : xyz =
let a = 0.055 in
let f (x: float) : float =
if x < 0.04045 then
x /. 12.92
else
((x +. a)/.(1. +. a))**2.4
in
let rl = f r in
let gl = f g in
let bl = f b in
let x = 0.4124*.rl +. 0.3576*.gl +. 0.1805*.bl in
let y = 0.2126*.rl +. 0.7152*.gl +. 0.0722*.bl in
let z = 0.0193*.rl +. 0.1192*.gl +. 0.9505*.bl in
XYZ(x, y, z)
let lab_of_xyz (XYZ(x, y, z) : xyz) : lab =
let XYZ(xn, yn, zn) = d65 in
let x = x /. xn in
let y = y /. yn in
let z = z /. zn in
let delta : float = 6./.29. in
let f (t: float) : float =
if t > delta ** 3. then
t ** (1. /. 3.)
else
t /. (3. *. delta ** 2.) +. 4. /. 29.
in
let l = 116. *. (f y) -. 16. in
let a = 500. *. (f x -. f y) in
let b = 200. *. (f y -. f z) in
Lab(l, a, b)
let lab_distance (Lab(l1, a1, b1) : lab) (Lab(l2, a2, b2) : lab) : float =
let sq (x: float) : float =
x *. x
in
sqrt(sq (l1 -. l2) +. sq (a1 -. a2) +. sq (b1 -. b2))
let lab_of_rgb (c: rgb) : lab =
c |> srgb_of_rgb |> xyz_of_srgb |> lab_of_xyz
let rgb_and_lab_of_rgb (c: rgb) : rgb * lab =
c, lab_of_rgb c
let palettes4 : (rgb*lab) Color4Map.t ColorPaletteMap.t =
List.fold_left
(fun acc (c, map) -> ColorPaletteMap.add c (Color4Map.map rgb_and_lab_of_rgb map) acc)
ColorPaletteMap.empty
Ocolor_palettes.[
VGA, vga;
CMD, cmd;
Terminal_app, terminal_app;
PuTTY, putty;
MIRC, mirc;
Xterm, xterm;
X, x;
Ubuntu, ubuntu;
]
let palette4 () : (rgb * lab) Color4Map.t =
((match Ocolor_config.get_palette () with
| Custom_palette p -> Color4Map.map rgb_and_lab_of_rgb p
| palette -> ColorPaletteMap.find palette palettes4)
[@warning "-4"])
let standard_palette8 : (rgb * lab) Color8Map.t =
let p : (rgb * lab) Color8Map.t = Color8Map.empty in
let p : (rgb * lab) Color8Map.t =
fold_greyscale
(fun gs p ->
Color8Map.add (Grayscale gs) (rgb_and_lab_of_rgb (gs*255/23, gs*255/23, gs*255/23)) p
)
p
in
let p : (rgb * lab) Color8Map.t =
fold_cube6
(fun ({r6; g6; b6} as c6) p ->
Color8Map.add (Cube6 c6) (rgb_and_lab_of_rgb (r6*255/5, g6*255/5, b6*255/5)) p
)
p
in
p
let palette8_of_palette4 (p: (rgb * lab) Color4Map.t) : (rgb * lab) Color8Map.t =
let p : (rgb * lab) Color8Map.t =
Color4Map.fold
(fun c lab acc ->
Color8Map.add (Standard c) lab acc
)
p
standard_palette8
in
p
let palettes8 : (rgb * lab) Color8Map.t ColorPaletteMap.t =
ColorPaletteMap.fold
(fun c map acc -> ColorPaletteMap.add c (palette8_of_palette4 map) acc)
palettes4
ColorPaletteMap.empty
let palette8 () : (rgb * lab) Color8Map.t =
((match Ocolor_config.get_palette () with
| Custom_palette p -> p |> Color4Map.map rgb_and_lab_of_rgb |> palette8_of_palette4
| palette -> ColorPaletteMap.find palette palettes8)
[@warning "-4"])
let closest_color4 (map: (rgb * lab) Color4Map.t) (c: rgb) : color4 * rgb * lab * float =
let (c4, (rgb, lab)) =
try
Color4Map.choose map
with Not_found -> failwith (Printf.sprintf "%s: empty palette" __LOC__)
in
let c = lab_of_rgb c in
let d = lab_distance lab c in
let c4, rgb, lab, distance =
Color4Map.fold
(
fun a (rgb, b) (min, rgb', argmin, d) ->
let d1 = lab_distance b c in
if d1 < d then
(a, rgb, b, d1)
else
(min, rgb', argmin, d)
)
map
(c4, rgb, lab, d)
in
c4, rgb, lab, distance
let closest_color4 (c: rgb) : color4 =
let c, _, _, _ = closest_color4 (palette4 ()) c in
c
let closest_color8 (map: (rgb * lab) Color8Map.t) (c: rgb) : color8 * rgb * lab =
let (a, (rgb, b)) =
try
Color8Map.choose map
with Not_found -> failwith (Printf.sprintf "%s: empty palette" __LOC__)
in
let c = lab_of_rgb c in
let d = lab_distance b c in
let a, rgb, b, _ =
Color8Map.fold
(
fun a (rgb, b) (min, rgb', argmin, d) ->
let d1 = lab_distance b c in
if d1 < d then
(a, rgb, b, d1)
else
(min, rgb', argmin, d)
)
map
(a, rgb, b, d)
in
a, rgb, b
let closest_color8 (c: rgb) : color8 =
let c, _, _ = closest_color8 (palette8 ()) c in
c
let rgb_of_color4 (c: color4) : rgb =
let p = palette4 () in
let (r, g, b), _ = Color4Map.find c p in
r, g, b