From 1b49b494ce30f973ca9d420d62debe267f0a7625 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johannes=20Sch=C3=B6nberger?= <jsch@demuc.de>
Date: Fri, 12 Sep 2014 16:51:16 -0400
Subject: [PATCH] Make error message for wrong input dim more explicit

---
 skimage/transform/_geometric.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/skimage/transform/_geometric.py b/skimage/transform/_geometric.py
index cf099c74..8af5588c 100644
--- a/skimage/transform/_geometric.py
+++ b/skimage/transform/_geometric.py
@@ -1168,7 +1168,9 @@ def warp(image, inverse_map=None, map_args={}, output_shape=None, order=1,
             coords = inverse_map
         else:
             if image.ndim < 2 or image.ndim > 3:
-                raise ValueError("Input must have 2 or 3 dimensions.")
+                raise ValueError("Only 2-D images (grayscale or color) are "
+                                 "supported, when providing a callable "
+                                 "`inverse_map`.")
 
             def coord_map(*args):
                 return inverse_map(*args, **map_args)