Add optimized tutorial cover images

server/tutorialImages.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, it } from "vitest";
+import {
+  buildTutorialImageFfmpegArgs,
+  buildTutorialImageKey,
+  buildTutorialImageUrl,
+  getTutorialImageSpec,
+} from "./tutorialImages";
+
+describe("tutorialImages", () => {
+  it("maps tennis categories to image specs", () => {
+    expect(getTutorialImageSpec("forehand")?.sourcePageUrl).toContain("Ray_Dunlop_forehand");
+    expect(getTutorialImageSpec("backhand")?.sourcePageUrl).toContain("Backhand_Federer");
+    expect(getTutorialImageSpec("serve")?.sourcePageUrl).toContain("Serena_Williams_Serves");
+    expect(getTutorialImageSpec("wall")?.sourcePageUrl).toContain("Tennis_wall");
+    expect(getTutorialImageSpec("unknown")).toBeNull();
+  });
+
+  it("builds stable storage keys and public URLs", () => {
+    expect(buildTutorialImageKey("forehand-fundamentals")).toBe("tutorials/forehand-fundamentals.webp");
+    expect(buildTutorialImageUrl("forehand-fundamentals")).toBe("/uploads/tutorials/forehand-fundamentals.webp");
+  });
+
+  it("uses a fixed compression pipeline for tutorial images", () => {
+    const args = buildTutorialImageFfmpegArgs("/tmp/input.jpg", "/tmp/output.webp");
+
+    expect(args).toEqual([
+      "-y",
+      "-i",
+      "/tmp/input.jpg",
+      "-vf",
+      "scale=1200:675:force_original_aspect_ratio=increase,crop=1200:675",
+      "-frames:v",
+      "1",
+      "-c:v",
+      "libwebp",
+      "-quality",
+      "78",
+      "-compression_level",
+      "6",
+      "/tmp/output.webp",
+    ]);
+  });
+});