feat: add image transform route with Sharp resize and crop

backend/src/routes/image.ts

@@ -0,0 +1,65 @@
+import { Router } from "express";
+import multer from "multer";
+import sharp from "sharp";
+import { TransformRequest } from "../types/image";
+
+const upload = multer({ storage: multer.memoryStorage() });
+const router = Router();
+
+router.post(
+  "/transform",
+  upload.single("file"),
+  async (req, res): Promise<void> => {
+    if (!req.file) {
+      res.status(400).json({ error: "No file uploaded" });
+      return;
+    }
+
+    const {
+      width,
+      height,
+      quality,
+      format = "png",
+      fit = "inside",
+      position = "center"
+    } = req.body as any;
+
+    const numericWidth = width ? Number(width) : undefined;
+    const numericHeight = height ? Number(height) : undefined;
+    const numericQuality = quality ? Number(quality) : 80;
+
+    try {
+      let image = sharp(req.file.buffer);
+
+      image = image.resize({
+        width: numericWidth,
+        height: numericHeight,
+        fit,       // "inside" (no crop) or "cover" (crop to fill)
+        position,  // where to crop when fit === "cover"
+        withoutEnlargement: true
+      });
+
+      if (format === "webp") {
+        image = image.webp({ quality: numericQuality });
+      } else if (format === "jpeg") {
+        image = image.jpeg({ quality: numericQuality });
+      } else {
+        image = image.png({ quality: numericQuality, compressionLevel: 9 });
+      }
+
+      const outputBuffer = await image.toBuffer();
+
+      res.setHeader("Content-Type", `image/${format}`);
+      res.setHeader(
+        "Content-Disposition",
+        `attachment; filename="output.${format}"`
+      );
+      res.send(outputBuffer);
+    } catch (err) {
+      console.error(err);
+      res.status(500).json({ error: "Image processing failed" });
+    }
+  }
+);
+
+export default router;