scikits-image/scikits-image — pull request #157 by tonysyu (2012-02-28 05:15:51+00:00)
Title: FIX: Check plugin is loaded before checking its functions.

When `io` functions (e.g. `io.imread`) is called with a non-default (i.e. not loaded by default) plugin, then they would fail.

For example, the following fails on my system:

```python
from skimage import data_dir
img_name = data_dir + '/camera.png'
import skimage.io as io
img = io.imread(img_name, plugin='freeimage')
```
But this works:

```python
io.use_plugin('freeimage')
img = io.imread(img_name)
```