first commit

server/gallery/color.ts

@@ -0,0 +1,93 @@
+export type GalleryColorFamily =
+    | "black"
+    | "blue"
+    | "green"
+    | "light"
+    | "orange"
+    | "purple"
+    | "red"
+    | "yellow";
+
+function hexToRgb(hex: string) {
+    const normalized = hex.trim().replace(/^#/, "");
+
+    if (!/^[0-9a-f]{6}$/i.test(normalized)) {
+        return null;
+    }
+
+    return {
+        r: parseInt(normalized.slice(0, 2), 16),
+        g: parseInt(normalized.slice(2, 4), 16),
+        b: parseInt(normalized.slice(4, 6), 16),
+    };
+}
+
+export function getGalleryColorFamily(
+    color: string | null | undefined,
+): GalleryColorFamily | null {
+    if (!color) {
+        return null;
+    }
+
+    const rgb = hexToRgb(color);
+
+    if (!rgb) {
+        return null;
+    }
+
+    const { r, g, b } = rgb;
+    const max = Math.max(r, g, b);
+    const min = Math.min(r, g, b);
+    const lightness = (max + min) / 510;
+
+    if (lightness > 0.78) {
+        return "light";
+    }
+
+    if (lightness < 0.2) {
+        return "black";
+    }
+
+    const delta = max - min;
+
+    if (delta < 24) {
+        return lightness > 0.52 ? "light" : "black";
+    }
+
+    let hue = 0;
+
+    if (max === r) {
+        hue = ((g - b) / delta) % 6;
+    } else if (max === g) {
+        hue = (b - r) / delta + 2;
+    } else {
+        hue = (r - g) / delta + 4;
+    }
+
+    hue = Math.round(hue * 60);
+
+    if (hue < 0) {
+        hue += 360;
+    }
+
+    if (hue < 18 || hue >= 345) {
+        return "red";
+    }
+    if (hue < 45) {
+        return "orange";
+    }
+    if (hue < 70) {
+        return "yellow";
+    }
+    if (hue < 170) {
+        return "green";
+    }
+    if (hue < 255) {
+        return "blue";
+    }
+    if (hue < 345) {
+        return "purple";
+    }
+
+    return null;
+}