Yes, indeed...

For instance,
```python
from skimage.filter import median filter
from skimage import data
from skimage import color
chelsea = data.chelsea()
greycat = color.rgb2grey(chelsea)
len(np.unique(greycat))
# Output is 32584
gfilt = median_filter(greycat)
gfilt.dtype
len(np.unique(gfilt))
# Output is 255
```
But it looks good!! (`pylab.imshow(gfilt)`)

The RGB channels of `chelsea` appear to have less than 255 "unique" values.