feat: add iOS support and harden receipt scanning

tests/e2e/sprint_c_image.test.ts

@@ -3,6 +3,7 @@
  */
 
 import { describe, test, expect } from "./runner";
+import sharp from "sharp";
 import {
   AI_IMAGE_LONG_EDGE_PX,
   AI_IMAGE_MIN_WIDTH_PX,
@@ -10,10 +11,12 @@ import {
 } from "../../src/lib/image/resize";
 import {
   contentBoundingBox,
+  detectPaperQuadrilateral,
   estimateSkewDegrees,
   needsContrastBoost,
+  paperReceiptBoundingBox,
 } from "../../src/lib/image/enhance";
-import { processReceiptImage } from "../../src/lib/image/processor";
+import { assessReceiptDetailQuality, processReceiptImage } from "../../src/lib/image/processor";
 
 describe("Sprint C — Mindestbreite", () => {
   test("Querformat bleibt am 1536-Long-Edge", () => {
@@ -86,6 +89,74 @@ describe("Sprint C — Crop", () => {
     const data = new Uint8Array(40 * 40).fill(200);
     expect(contentBoundingBox(data, 40, 40)).toBeNull();
   });
+
+  test("heller Thermobon wird auf strukturiertem farbigem Untergrund erkannt", () => {
+    const w = 100;
+    const h = 140;
+    const data = new Uint8Array(w * h * 3);
+    for (let y = 0; y < h; y++) {
+      for (let x = 0; x < w; x++) {
+        const i = (y * w + x) * 3;
+        const onPaper = x >= 32 && x < 68;
+        data[i] = onPaper ? 200 : 180;
+        data[i + 1] = onPaper ? 207 : 132;
+        data[i + 2] = onPaper ? 214 : 82;
+      }
+    }
+    const box = paperReceiptBoundingBox(data, w, h, 3);
+    expect(box).not.toBeNull();
+    expect(box!.left).toBeLessThanOrEqual(32);
+    expect(box!.left + box!.width).toBeGreaterThanOrEqual(68);
+    expect(box!.width).toBeLessThan(60);
+  });
+
+  test("Perspektive, Schatten, Falte und gemusterter Untergrund werden konservativ erkannt", () => {
+    const w = 120;
+    const h = 180;
+    const data = new Uint8Array(w * h * 3);
+    for (let y = 0; y < h; y++) {
+      const progress = y / (h - 1);
+      const left = Math.round(32 - progress * 10);
+      const right = Math.round(88 + progress * 10);
+      for (let x = 0; x < w; x++) {
+        const offset = (y * w + x) * 3;
+        const onPaper = x >= left && x <= right;
+        const folded = Math.abs(y - 92) < 2;
+        const shadow = 165 + Math.round(progress * 65);
+        data[offset] = onPaper ? (folded ? 125 : shadow) : 115 + ((x + y) % 18);
+        data[offset + 1] = onPaper ? (folded ? 125 : shadow) : 72 + ((x * 3 + y) % 14);
+        data[offset + 2] = onPaper ? (folded ? 125 : shadow) : 35 + ((x + y * 2) % 11);
+      }
+    }
+    const quad = detectPaperQuadrilateral(data, w, h, 3);
+    expect(quad).not.toBeNull();
+    expect(quad!.topLeft.x).toBeGreaterThan(quad!.bottomLeft.x);
+    expect(quad!.topRight.x).toBeLessThan(quad!.bottomRight.x);
+    expect(quad!.confidence).toBeGreaterThanOrEqual(0.72);
+  });
+
+  test("unsichere helle Vollfläche wird nicht als Perspektivkorrektur behandelt", () => {
+    const data = new Uint8Array(100 * 140 * 3).fill(220);
+    expect(detectPaperQuadrilateral(data, 100, 140, 3)).toBeNull();
+  });
+});
+
+describe("Sprint C — lokale Lesbarkeit", () => {
+  test("Unschärfe erhält einen niedrigeren Qualitätswert als klare Druckzeilen", async () => {
+    const width = 200;
+    const height = 300;
+    const raw = Buffer.alloc(width * height, 235);
+    for (let y = 12; y < height - 12; y += 18) {
+      for (let yy = y; yy < y + 3; yy++) {
+        raw.fill(25, yy * width + 18, yy * width + width - 18);
+      }
+    }
+    const crisp = await sharp(raw, { raw: { width, height, channels: 1 } }).jpeg().toBuffer();
+    const blurred = await sharp(crisp).blur(4).jpeg().toBuffer();
+    expect(await assessReceiptDetailQuality(crisp)).toBeGreaterThan(
+      await assessReceiptDetailQuality(blurred)
+    );
+  });
 });
 
 describe("Sprint C — Deskew", () => {