ENH: Throw exception if image cannot be read (#738)

* ENH: Throw exception if image cannot be read

Non-existent files are caught but empty / bad files caused a seg fault

ants/core/ants_image_io.py

@@ -58,7 +58,7 @@
             ita = _image_type_map[itype]
             pa = _ptype_type_map[p]
             _image_read_dict[itype][p][d] = "imageRead%s%s%i" % (ita, pa, d)
-    
+
 def from_numpy(
     data, origin=None, spacing=None, direction=None, has_components=False, is_rgb=False
 ):
@@ -89,16 +89,16 @@ def from_numpy(
     ANTsImage
         image with given data and any given information
     """
-    
+
     # this is historic but should be removed once tests can pass without it
     if data.dtype.name == 'float64':
         data = data.astype('float32')
-    
+
     # if dtype is not supported, cast to best available
     best_dtype = infer_dtype(data.dtype)
     if best_dtype != data.dtype:
         data = data.astype(best_dtype)
-    
+
     img = _from_numpy(data.T.copy(), origin, spacing, direction, has_components, is_rgb)
     return img
 
@@ -248,7 +248,6 @@ def image_header_info(filename):
     retval["direction"] = np.round(retval["direction"], 4)
     return retval
 
-
 def image_clone(image, pixeltype=None):
     """
     Clone an ANTsImage
@@ -493,7 +492,7 @@ def clone(image, pixeltype=None):
         libfn = get_lib_fn('antsImageClone%s'%fn_suffix)
         pointer_cloned = libfn(image.pointer)
         return ants.from_pointer(pointer_cloned)
-        
+
 copy = clone
 
 @image_method
@@ -525,6 +524,6 @@ def new_image_like(image, data):
     return from_numpy(data, origin=image.origin,
         spacing=image.spacing, direction=image.direction,
         has_components=image.has_components)
-    
+
 def from_numpy_like(data, image):
     return new_image_like(image, data)

src/antsImageHeaderInfo.cxx

@@ -24,6 +24,11 @@ nb::dict antsImageHeaderInfo( std::string fname )
       itk::ImageIOFactory::CreateImageIO(
           fname.c_str(), itk::ImageIOFactory::ReadMode);
 
+  if ( !imageIO )
+    {
+    throw std::runtime_error("Could not create ImageIO object for file " + fname);
+    }
+
   imageIO->SetFileName(fname);
   imageIO->ReadImageInformation();
 

tests/test_core_ants_image_io.py

@@ -339,8 +339,14 @@ def test_image_read_write(self):
             nptest.assert_allclose(img.numpy(), img2.numpy())
 
         # non-existant file
-        with self.assertRaises(Exception):
+        with self.assertRaises(ValueError):
+            tmpfile = mktemp(suffix='.nii.gz')
+            ants.image_read(tmpfile)
+
+        # Test empty file
+        with self.assertRaises(RuntimeError):
             tmpfile = mktemp(suffix='.nii.gz')
+            open(tmpfile, 'a').close()
             ants.image_read(tmpfile)