1 files changed, 38 insertions, 0 deletions
diff --git a/src/Color.ml b/src/Color.ml
new file mode 100644
index 0000000..b3d2f91
--- /dev/null
+++ b/src/Color.ml
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+let from_sRGB sRGB =
+  if sRGB <= 0.03928 then
+    sRGB /. 12.92
+  else
+    ((sRGB +. 0.055) /. 1.055) ** 2.4
+
+type rgb =
+  { r: float
+  ; g: float
+  ; b: float
+  }
+
+(* https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef *)
+let relativeLuminance (c: rgb) =
+  0.2126 *. from_sRGB (c.r /. 255.) +. 0.7152 *. from_sRGB (c.g /. 255.) +. 0.0722 *. from_sRGB (c.b /. 255.)
+
+(* https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrastratio *)
+let contrast_ratio (c1: rgb) (c2: rgb) =
+  let rl1 = relativeLuminance c1  in
+  let rl2 = relativeLuminance c2 in
+
+  if (rl1 > rl2) then
+    (rl1 +. 0.05) /. (rl2 +. 0.05)
+  else
+    (rl2 +. 0.05) /. (rl1 +. 0.05)
+
+let from_raw color =
+  let get_opt = function | Some x -> x | None -> raise (Invalid_argument "Option.get") in
+  let div = H.div [| HA.style ("color: " ^ color) |] [| |] in
+  let body = Document.querySelectorUnsafe "body" in
+  let () = Element.appendChild body div in
+  let rgb = [%raw {| window.getComputedStyle(div).color |}] in
+  let () = Element.removeChild body div in
+  let xs = Js.String.split ", " (get_opt (Js.String.splitByRe [%re "/[()]/"] rgb).(1)) in
+  { r = Js.Float.fromString xs.(0)
+  ; g = Js.Float.fromString xs.(1)
+  ; b = Js.Float.fromString xs.(2)
+  }