Initial commit

build/dev/javascript/gleam_community_colour/gleam_community/colour/accessibility.mjs

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+import * as $float from "../../../gleam_stdlib/gleam/float.mjs";
+import * as $list from "../../../gleam_stdlib/gleam/list.mjs";
+import { Ok, makeError, divideFloat } from "../../gleam.mjs";
+import * as $colour from "../../gleam_community/colour.mjs";
+
+const FILEPATH = "src/gleam_community/colour/accessibility.gleam";
+
+function intensity(colour_value) {
+  let $ = true;
+  if (colour_value <= 0.03928) {
+    return colour_value / 12.92;
+  } else {
+    let $1 = $float.power((colour_value + 0.055) / 1.055, 2.4);
+    let i;
+    if ($1 instanceof Ok) {
+      i = $1[0];
+    } else {
+      throw makeError(
+        "let_assert",
+        FILEPATH,
+        "gleam_community/colour/accessibility",
+        62,
+        "intensity",
+        "Pattern match failed, no pattern matched the value.",
+        {
+          value: $1,
+          start: 2399,
+          end: 2470,
+          pattern_start: 2410,
+          pattern_end: 2415
+        }
+      )
+    }
+    return i;
+  }
+}
+
+/**
+ * Returns the relative brightness of the given `Colour` as a `Float` between
+ * 0.0, and 1.0 with 0.0 being the darkest possible colour and 1.0 being the lightest.
+ *
+ * <details>
+ * <summary>Example:</summary>
+ *
+ * ```gleam
+ * fn example() {
+ *   luminance(colour.white) // 1.0
+ * }
+ * ```
+ * </details>
+ *
+ * <div style="position: relative;">
+ *     <a style="position: absolute; left: 0;" href="https://github.com/gleam-community/colour/issues">
+ *         <small>Spot a typo? Open an issue!</small>
+ *     </a>
+ *     <a style="position: absolute; right: 0;" href="#">
+ *         <small>Back to top ↑</small>
+ *     </a>
+ * </div>
+ */
+export function luminance(colour) {
+  let $ = $colour.to_rgba(colour);
+  let r;
+  let g;
+  let b;
+  r = $[0];
+  g = $[1];
+  b = $[2];
+  let r_intensity = intensity(r);
+  let g_intensity = intensity(g);
+  let b_intensity = intensity(b);
+  return ((0.2126 * r_intensity) + (0.7152 * g_intensity)) + (0.0722 * b_intensity);
+}
+
+/**
+ * Returns the contrast between two `Colour` values as a `Float` between 1.0,
+ * and 21.0 with 1.0 being no contrast and, 21.0 being the highest possible contrast.
+ *
+ * <details>
+ * <summary>Example:</summary>
+ *
+ * ```gleam
+ * fn example() {
+ *   contrast_ratio(between: colour.white, and: colour.black) // 21.0
+ * }
+ * ```
+ * </details>
+ *
+ * <div style="position: relative;">
+ *     <a style="position: absolute; left: 0;" href="https://github.com/gleam-community/colour/issues">
+ *         <small>Spot a typo? Open an issue!</small>
+ *     </a>
+ *     <a style="position: absolute; right: 0;" href="#">
+ *         <small>Back to top ↑</small>
+ *     </a>
+ * </div>
+ */
+export function contrast_ratio(colour_a, colour_b) {
+  let luminance_a = luminance(colour_a) + 0.05;
+  let luminance_b = luminance(colour_b) + 0.05;
+  let $ = luminance_a > luminance_b;
+  if ($) {
+    return divideFloat(luminance_a, luminance_b);
+  } else {
+    return divideFloat(luminance_b, luminance_a);
+  }
+}
+
+/**
+ * Returns the `Colour` with the highest contrast between the base `Colour`,
+ * and and the other provided `Colour` values.
+ *
+ * <details>
+ * <summary>Example:</summary>
+ *
+ * ```gleam
+ * fn example() {
+ *   maximum_contrast(
+ *    colour.yellow,
+ *    [colour.white, colour.dark_blue, colour.green],
+ *  )
+ * }
+ * ```
+ * </details>
+ *
+ * <div style="position: relative;">
+ *     <a style="position: absolute; left: 0;" href="https://github.com/gleam-community/colour/issues">
+ *         <small>Spot a typo? Open an issue!</small>
+ *     </a>
+ *     <a style="position: absolute; right: 0;" href="#">
+ *         <small>Back to top ↑</small>
+ *     </a>
+ * </div>
+ */
+export function maximum_contrast(base, colours) {
+  let _pipe = colours;
+  let _pipe$1 = $list.sort(
+    _pipe,
+    (colour_a, colour_b) => {
+      let contrast_a = contrast_ratio(base, colour_a);
+      let contrast_b = contrast_ratio(base, colour_b);
+      return $float.compare(contrast_b, contrast_a);
+    },
+  );
+  return $list.first(_pipe$1);
+}