update

app.py

@@ -7,10 +7,36 @@ from PIL import Image
 from itertools import product
 
 def show_preview(image):
-    """Show uploaded image, converted to RGB for reliable preview rendering."""
+    """Render uploaded image faithfully, including 16-bit/single-channel inputs.
+
+    - RGB/RGBA: show as-is (strip alpha)
+    - 16-bit or single-channel: min-max (or 1-99%ile) normalize to 8-bit for display
+    """
     if image is None:
         return None
     try:
+        arr = np.array(image)
+        # RGBA → RGB
+        if arr.ndim == 3 and arr.shape[2] == 4:
+            return image.convert("RGB")
+        # RGB → as-is
+        if arr.ndim == 3 and arr.shape[2] == 3:
+            return image
+        # Single-channel or higher bit-depth
+        if arr.ndim == 2 or (arr.ndim == 3 and arr.shape[2] == 1):
+            if arr.ndim == 3:
+                arr = arr[..., 0]
+            a = np.nan_to_num(arr.astype(np.float64), nan=0.0, posinf=0.0, neginf=0.0)
+            # Robust contrast stretch
+            vmin = np.percentile(a, 1.0)
+            vmax = np.percentile(a, 99.0)
+            if not np.isfinite(vmin) or not np.isfinite(vmax) or vmax <= vmin:
+                vmin, vmax = float(np.min(a)), float(np.max(a))
+            denom = max(vmax - vmin, 1e-6)
+            vis = np.clip((a - vmin) / denom, 0.0, 1.0) * 255.0
+            vis8 = vis.astype(np.uint8)
+            return Image.fromarray(vis8, mode='L')
+        # Fallback
         return image.convert("RGB")
     except Exception:
         return image