add pie chart example

apps/color-buddy/public/examples/pie-chart.json

@@ -0,0 +1,29 @@
+{
+  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
+  "description": "A simple pie chart with labels.",
+  "data": {
+    "values": [
+      { "category": "a", "value": 4 },
+      { "category": "b", "value": 6 },
+      { "category": "c", "value": 10 },
+      { "category": "d", "value": 3 },
+      { "category": "e", "value": 7 },
+      { "category": "f", "value": 8 }
+    ]
+  },
+  "encoding": {
+    "theta": { "field": "value", "type": "quantitative", "stack": true },
+    "color": { "field": "category", "type": "nominal", "legend": null }
+  },
+  "layer": [
+    {
+      "mark": { "type": "arc", "outerRadius": 80 }
+    },
+    {
+      "mark": { "type": "text", "radius": 90 },
+      "encoding": {
+        "text": { "field": "category", "type": "nominal" }
+      }
+    }
+  ]
+}

apps/color-buddy/src/stores/example-store.ts

@@ -29,6 +29,11 @@ export const DEMOS = [
     title: "Bar Chart",
     filename: "./examples/grouped-bar-chart.json",
   },
+  {
+    type: "vega",
+    title: "Pie Chart",
+    filename: "./examples/pie-chart.json",
+  },
   { type: "vega", title: "Heatmap", filename: "./examples/heatmap.json" },
   { type: "vega", title: "Map", filename: "./examples/illinois-map.json" },
   {

packages/palette/src/Color.ts

@@ -139,6 +139,11 @@ export class Color {
     return this.toColorIO().luminance;
   }
   deltaE(color: Color, algorithm: DistAlgorithm = "2000"): number {
+    const allowedAlgorithms = new Set(["76", "CMC", "2000", "ITP", "Jz", "OK"]);
+    if (!allowedAlgorithms.has(algorithm)) {
+      return 0;
+    }
+
     const left = this.toColorIO().to("srgb");
     const right = color.toColorIO().to("srgb");
     return left.deltaE(right, algorithm);