Use current image for line profile


Originated from:

```
---------- Forwarded message ----------
From: Nadav Horesh <nadavh.horesh@gmail.com>
Date: Tue, May 27, 2014 at 3:47 AM
Subject: Updating LinePorofile on image changed
To: scikit-image@googlegroups.com


Hi,

 I built an application based on skimage viewer some image filter plugins and a LineProfile. In this application I want to investigate the influence of the filters (tuned by some attached sliders) via the LineProfile tool. My problem is that the tool sees only the original image, and not those generated (and displayed in viewer window) by the filters.

 How can I make the LineProfile tool relate to the modified image?

  Thanks,

    Nadav.
```

Now it will default to the current image instead of the original.  Do we want to add the option of which one to use?