Fix handling of ImageCollection indexing and add test

skimage/io/collection.py

@@ -254,13 +254,16 @@ class ImageCollection(object):
 
             if ((self.conserve_memory and n != self._cached) or
                     (self.data[idx] is None)):
+                kwargs = self.load_func_kwargs
                 if self._frame_index:
                     fname, img_num = self._frame_index[n]
-                    self.data[idx] = self.load_func(fname, img_num=img_num,
-                                                    **self.load_func_kwargs)
+                    if img_num > 0:
+                        self.data[idx] = self.load_func(fname, img_num=img_num,
+                                                        **kwargs)
+                    else:
+                        self.data[idx] = self.load_func(fname, **kwargs)
                 else:
-                    self.data[idx] = self.load_func(self.files[n],
-                                                    **self.load_func_kwargs)
+                    self.data[idx] = self.load_func(self.files[n], **kwargs)
                 self._cached = n
 
             return self.data[idx]

skimage/io/tests/test_freeimage.py

@@ -1,6 +1,7 @@
 import os
 import skimage as si
 import skimage.io as sio
+from skimage import data_dir
 import numpy as np
 
 from numpy.testing import *
@@ -12,6 +13,7 @@ try:
     FI_available = True
     sio.use_plugin('freeimage')
 except RuntimeError:
+    raise
     FI_available = False
 
 np.random.seed(0)
@@ -112,5 +114,13 @@ def test_metadata():
     assert meta[1][('EXIF_MAIN', 'Software')].startswith('I')
 
 
+@skipif(not FI_available)
+def test_collection():
+    pattern = [os.path.join(data_dir, pic)
+               for pic in ['camera.png', 'color.png']]
+    images = sio.ImageCollection(pattern)
+    assert len(images) == 2
+    assert len(images[:]) == 2
+
 if __name__ == "__main__":
     run_module_suite()