Panorama stitchers, feathering, seaming etc..

[Bruno Postle]

On Wed 29-Oct-2003 at 08:00:28AM -0500, Ed Halley wrote:
> > Am 19.10.03, 21:29 +0100 schrieb Bruno Postle:
> > >     http://bugbear.blackfish.org.uk/~bruno/feathering/
> 
> It looks like you need to add a feathered region to the overridden
> colors.  That is, when combining two images' colors, make a new map
> which is 0 for "use the credibility ratio to blend this pixel" and 1 for
> "use only the most credible source for this pixel".  Then gaussian blur
> this map, and double any number (so that the 1s stay 1 but the 0s are
> gradually blended up to it).  Then use that as a ratio between the
> credibility mix and the overridden mix.

Yes, between a blended pixel and an adjacent un-blended pixel (where
only the most credible pixel is drawn); the contrast is high enough
to cause a visual discontinuity.  The final example I created
ended-up with some nasty sharp edges even though the original
photographs were not very sharp at all.

A similar fix could be obtained by weighting each blended pixel
towards any adjacent pixels that would otherwise be not-blended.

In general I'm not entirely convinced that this 'credibility map'
system is the right way to go, since there are a couple of
drawbacks:

   - A lot of the time, the feather-width should actually be very
     narrow because big merged areas look blurred.

   - The threshold level that determines the action for each pixel
     is subjective - Yet another variable in the system.

   - The 'credibility map' really needs to be radial from the centre
     of the photo - It would be perfect for circular fisheye photos,
     but it isn't so good for rectangular images.

-- 
Bruno