refactor(media): share image resize side grid and quality steps

src/media/image-ops.helpers.test.ts

@@ -0,0 +1,18 @@
+import { describe, expect, it } from "vitest";
+import { buildImageResizeSideGrid, IMAGE_REDUCE_QUALITY_STEPS } from "./image-ops.js";
+
+describe("buildImageResizeSideGrid", () => {
+  it("returns descending unique sides capped by maxSide", () => {
+    expect(buildImageResizeSideGrid(1200, 900)).toEqual([1200, 1000, 900, 800]);
+  });
+
+  it("keeps only positive side values", () => {
+    expect(buildImageResizeSideGrid(0, 0)).toEqual([]);
+  });
+});
+
+describe("IMAGE_REDUCE_QUALITY_STEPS", () => {
+  it("keeps expected quality ladder", () => {
+    expect([...IMAGE_REDUCE_QUALITY_STEPS]).toEqual([85, 75, 65, 55, 45, 35]);
+  });
+});

src/media/image-ops.ts

@@ -10,6 +10,15 @@ export type ImageMetadata = {
   height: number;
 };
 
+export const IMAGE_REDUCE_QUALITY_STEPS = [85, 75, 65, 55, 45, 35] as const;
+
+export function buildImageResizeSideGrid(maxSide: number, sideStart: number): number[] {
+  return [sideStart, 1800, 1600, 1400, 1200, 1000, 800]
+    .map((value) => Math.min(maxSide, value))
+    .filter((value, idx, arr) => value > 0 && arr.indexOf(value) === idx)
+    .toSorted((a, b) => b - a);
+}
+
 function isBun(): boolean {
   return typeof (process.versions as { bun?: unknown }).bun === "string";
 }