feat(image-import): add compressImage with canvas resize + JPEG re-encode

image-import.js

@@ -11,6 +11,57 @@ class ImageImporter {
         this.session = null;
         this.abortController = null;
     }
+
+    /**
+     * Resize image so the longest edge is <= 2048 px, re-encode as JPEG q=0.85.
+     * @param {File|Blob} file
+     * @returns {Promise<{blob: Blob, dataUrl: string, width: number, height: number}>}
+     */
+    async compressImage(file) {
+        const objUrl = URL.createObjectURL(file);
+        try {
+            const img = await new Promise((resolve, reject) => {
+                const i = new Image();
+                i.onload = () => resolve(i);
+                i.onerror = () => reject(new Error('Bild konnte nicht geladen werden'));
+                i.src = objUrl;
+            });
+
+            const longest = Math.max(img.width, img.height);
+            let newW = img.width;
+            let newH = img.height;
+            if (longest > 2048) {
+                const scale = 2048 / longest;
+                newW = Math.round(img.width * scale);
+                newH = Math.round(img.height * scale);
+            }
+
+            const canvas = document.createElement('canvas');
+            canvas.width = newW;
+            canvas.height = newH;
+            const ctx = canvas.getContext('2d');
+            ctx.drawImage(img, 0, 0, newW, newH);
+
+            const blob = await new Promise((resolve, reject) => {
+                canvas.toBlob(
+                    (b) => b ? resolve(b) : reject(new Error('toBlob fehlgeschlagen')),
+                    'image/jpeg',
+                    0.85
+                );
+            });
+
+            const dataUrl = await new Promise((resolve, reject) => {
+                const reader = new FileReader();
+                reader.onload = () => resolve(reader.result);
+                reader.onerror = () => reject(new Error('FileReader fehlgeschlagen'));
+                reader.readAsDataURL(blob);
+            });
+
+            return { blob, dataUrl, width: newW, height: newH };
+        } finally {
+            URL.revokeObjectURL(objUrl);
+        }
+    }
 }
 
 // Make available globally

test-suite.js

@@ -527,6 +527,52 @@ runner.test('Storage API Key: clearAll laesst API-Key unberuehrt', (t) => {
     storage.clearApiKey();
 });
 
+// ============================================================================
+// ImageImporter Tests - Preprocessing (Feature A)
+// ============================================================================
+
+/**
+ * Helper: build a synthetic image File from a canvas.
+ */
+async function makeTestImageFile(width, height, mime = 'image/png') {
+    const canvas = document.createElement('canvas');
+    canvas.width = width;
+    canvas.height = height;
+    const ctx = canvas.getContext('2d');
+    ctx.fillStyle = '#3366cc';
+    ctx.fillRect(0, 0, width, height);
+    ctx.fillStyle = '#ffffff';
+    ctx.font = '32px sans-serif';
+    ctx.fillText('TEST', 20, 50);
+    const blob = await new Promise(res => canvas.toBlob(res, mime));
+    return new File([blob], 'test.png', { type: mime });
+}
+
+runner.test('Preprocess: 4000x3000 wird auf laengste Kante 2048 skaliert', async (t) => {
+    const importer = new ImageImporter(null);
+    const file = await makeTestImageFile(4000, 3000);
+    const result = await importer.compressImage(file);
+    t.assertEqual(result.width, 2048, 'Breite sollte 2048 sein');
+    t.assertEqual(result.height, 1536, 'Hoehe sollte 1536 sein (Seitenverhaeltnis erhalten)');
+    t.assertTrue(result.dataUrl.startsWith('data:image/jpeg;base64,'), 'dataUrl-Prefix korrekt');
+});
+
+runner.test('Preprocess: 800x600 bleibt unveraendert (kein Upscale)', async (t) => {
+    const importer = new ImageImporter(null);
+    const file = await makeTestImageFile(800, 600);
+    const result = await importer.compressImage(file);
+    t.assertEqual(result.width, 800, 'Breite unveraendert');
+    t.assertEqual(result.height, 600, 'Hoehe unveraendert');
+});
+
+runner.test('Preprocess: Output ist immer JPEG', async (t) => {
+    const importer = new ImageImporter(null);
+    const file = await makeTestImageFile(500, 500, 'image/png');
+    const result = await importer.compressImage(file);
+    t.assertTrue(result.dataUrl.startsWith('data:image/jpeg;base64,'), 'Output ist JPEG');
+    t.assertTrue(result.dataUrl.length > 1000, 'Output-Laenge > 1KB');
+});
+
 // ============================================================================
 // Display Functions
 // ============================================================================

test.html

@@ -142,6 +142,7 @@
     <script src="holidays.js"></script>
     <script src="calculator.js"></script>
     <script src="storage.js"></script>
+    <script src="image-import.js"></script>
     <script src="test-suite.js"></script>
 </body>
 </html>