Merge pull request #1 from sunnywalker/sunnywalker-contrasting-color

Add files via upload

Scripts/contrastingColor.js

@@ -0,0 +1,65 @@
+/**
+{
+    "api": 1,
+    "name": "Contrasting Color",
+    "description": "Determine whether black or white contrasts better with the given color(s) (one per line).",
+    "author": "Sunny Walker",
+    "icon": "table",
+    "tags": "contrast,color,wcag"
+}
+**/
+
+function main(input) {
+  let lines = input.fullText.split("\n");
+  let o = lines.map(c => betterColor(c));
+  input.fullText = o.join("\n");
+}
+
+// convert #rrggbb into its integer r, g, b components
+const hex2Rgb = hex => {
+  const rgb = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
+  return rgb ? {
+    r: parseInt(rgb[1], 16),
+    g: parseInt(rgb[2], 16),
+    b: parseInt(rgb[3], 16)
+  } : null;
+};
+
+// calculate the luminance of a color
+const luminance = hex => {
+  var rgb = hex2Rgb(hex);
+  var a = [rgb.r, rgb.g, rgb.b].map(v => {
+    v /= 255;
+    return (v <= 0.03928) ? v / 12.92 : Math.pow(((v + 0.055) / 1.055), 2.4);
+  });
+  return a[0] * 0.2126 + a[1] * 0.7152 + a[2] * 0.0722;
+};
+
+// calculate the contrast ratio between two colors
+const contrast = (c1, c2) => {
+  const l1 = luminance(c1) + .05;
+  const l2 = luminance(c2) + .05;
+  let ratio = l1 / l2;
+  if (l2 > l1) {
+    ratio = 1 / ratio;
+  }
+  return Math.floor(ratio * 100) / 100;
+};
+
+// convert #rbg to #rrggbb
+const normalizeHex = hex => hex.replace(/^#?([a-f\d])([a-f\d])([a-f\d])$/i, '#$1$1$2$2$3$3');
+
+// determine the WCAG 2.0 contrast ratio level
+const wcagLevel = ratio => ratio >= 7 ? 'AAA' : ratio >= 4.5 ? 'AA' : 'fail';
+
+// determine the better contrasting color for a color
+const betterColor = hex => {
+  const h = normalizeHex(hex);
+  if (!h.match(/^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i)) {
+    return hex;
+  }
+  var w = contrast(h, '#ffffff');
+  var b = contrast(h, '#000000');
+  var r = Math.max(w, b);
+  return hex + ' // contrasts best with ' + (w > b ? '#fff' : '#000') + ' with a ratio of ' + r + ' to 1; WCAG 2.0: ' + wcagLevel(r);
+};