Config Page

test/readJpegWidth.test.js

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+'use strict';
+
+const { readJpegWidth } = require('../src/cameraSwitch');
+
+// Minimaler JPEG-Kopf: SOI (FFD8) + SOF-Marker mit Höhe/Breite.
+// SOF-Layout: FF Cx | len(2) | precision(1) | height(2) | width(2)
+function jpegWithWidth(width, height = 480, marker = 0xC0) {
+  const b = Buffer.alloc(20, 0);
+  b[0] = 0xFF; b[1] = 0xD8;        // SOI
+  b[2] = 0xFF; b[3] = marker;      // SOF0 / SOF2
+  b.writeUInt16BE(17, 4);          // Segment-Länge
+  b[6] = 8;                        // precision
+  b.writeUInt16BE(height, 7);      // Höhe
+  b.writeUInt16BE(width, 9);       // Breite
+  return b;
+}
+
+describe('readJpegWidth', () => {
+  test('liest Breite aus SOF0 (baseline)', () => {
+    expect(readJpegWidth(jpegWithWidth(320))).toBe(320);
+    expect(readJpegWidth(jpegWithWidth(1920))).toBe(1920);
+  });
+
+  test('liest Breite aus SOF2 (progressive)', () => {
+    expect(readJpegWidth(jpegWithWidth(1280, 720, 0xC2))).toBe(1280);
+  });
+
+  test('kein SOF-Marker → null', () => {
+    const b = Buffer.from([0xFF, 0xD8, 0xFF, 0xD9, 0, 0, 0, 0, 0, 0, 0, 0]);
+    expect(readJpegWidth(b)).toBeNull();
+  });
+});