Update app.py

app.py

@@ -166,7 +166,11 @@ def extract_middle_slices(nifti_path, output_image_path, slice_size=180, center=
 
     # Choose colormap
     if label_components:
-        cmap = plt.cm.Pastel1  # Colorful
+        # Build a modified Pastel colormap with 0 = black
+        pastel = plt.cm.Pastel2(np.linspace(0, 1, 256))
+        pastel[0] = np.array([0, 0, 0, 1])  # Set the first color (label 0) to black (RGBA)
+        custom_cmap = mpl.colors.ListedColormap(pastel)
+        cmap = custom_cmap  # Colorful
         vmin = 0
         vmax = num_features
     else: