fix(dewarp): change manual slider to percentage (0-200%) instead of raw multiplier

The old -3.0 to +3.0 scale multiplied the full displacement map (up to ~79px)
directly, causing extreme distortion at values >1. New slider:
- 0% = no correction
- 100% = auto-detected correction (default)
- 200% = double correction
- Step size: 5%

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

admin-lehrer/components/ocr-pipeline/DewarpControls.tsx

@@ -29,7 +29,7 @@ export function DewarpControls({
   onNext,
   isApplying,
 }: DewarpControlsProps) {
-  const [manualScale, setManualScale] = useState(0)
+  const [manualScale, setManualScale] = useState(100)
   const [gtFeedback, setGtFeedback] = useState<'correct' | 'incorrect' | null>(null)
   const [gtNotes, setGtNotes] = useState('')
   const [gtSaved, setGtSaved] = useState(false)
@@ -94,22 +94,22 @@ export function DewarpControls({
       {/* Manual scale slider */}
       {dewarpResult && (
         <div className="bg-white dark:bg-gray-800 rounded-lg border border-gray-200 dark:border-gray-700 p-4">
-          <div className="text-sm font-medium text-gray-700 dark:text-gray-300 mb-2">Manuelle Staerke</div>
+          <div className="text-sm font-medium text-gray-700 dark:text-gray-300 mb-2">Korrekturstaerke</div>
           <div className="flex items-center gap-3">
-            <span className="text-xs text-gray-400 w-8 text-right">-3.0</span>
+            <span className="text-xs text-gray-400 w-8 text-right">0%</span>
             <input
               type="range"
-              min={-3}
+              min={0}
-              max={3}
+              max={200}
-              step={0.1}
+              step={5}
               value={manualScale}
-              onChange={(e) => setManualScale(parseFloat(e.target.value))}
+              onChange={(e) => setManualScale(parseInt(e.target.value))}
               className="flex-1 h-2 bg-gray-200 rounded-lg appearance-none cursor-pointer dark:bg-gray-700 accent-teal-500"
             />
-            <span className="text-xs text-gray-400 w-8">+3.0</span>
+            <span className="text-xs text-gray-400 w-10">200%</span>
-            <span className="font-mono text-sm w-14 text-right">{manualScale.toFixed(1)}</span>
+            <span className="font-mono text-sm w-14 text-right">{manualScale}%</span>
             <button
-              onClick={() => onManualDewarp(manualScale)}
+              onClick={() => onManualDewarp(manualScale / 100)}
               disabled={isApplying}
               className="px-3 py-1.5 text-sm bg-teal-600 text-white rounded-md hover:bg-teal-700 disabled:opacity-50 transition-colors"
             >
@@ -117,7 +117,7 @@ export function DewarpControls({
             </button>
           </div>
           <p className="text-xs text-gray-400 mt-1">
-            0 = keine Korrektur, positiv = nach rechts entzerren, negativ = nach links
+            100% = automatisch erkannte Korrektur, 0% = keine, 200% = doppelt so stark
           </p>
         </div>
       )}

klausur-service/backend/cv_vocab_pipeline.py

@@ -668,13 +668,13 @@ def dewarp_image_manual(img: np.ndarray, displacement_map: np.ndarray,
     Args:
         img: BGR image (deskewed, before dewarp).
         displacement_map: The displacement map from auto-dewarp.
-        scale: Manual scale factor (-3.0 to +3.0).
+        scale: Fraction of auto-detected correction (0.0 = none, 1.0 = auto, 2.0 = double).
 
     Returns:
         Corrected image.
     """
-    scale = max(-3.0, min(3.0, scale))
+    scale = max(0.0, min(2.0, scale))
-    if abs(scale) < 0.01:
+    if scale < 0.01:
         return img
     return _apply_displacement_map(img, displacement_map, scale=scale)
 

klausur-service/backend/ocr_pipeline_api.py

@@ -400,9 +400,9 @@ async def manual_dewarp(session_id: str, req: ManualDewarpRequest):
     if deskewed_bgr is None:
         raise HTTPException(status_code=400, detail="Deskew must be completed before dewarp")
 
-    scale = max(-3.0, min(3.0, req.scale))
+    scale = max(0.0, min(2.0, req.scale))
 
-    if displacement_map is None or abs(scale) < 0.01:
+    if displacement_map is None or scale < 0.01:
         # No displacement map or zero scale — use deskewed as-is
         dewarped_bgr = deskewed_bgr
     else: