[ptx] Band Blending [was: Hugin wishlist, RFC]

[Kai-Uwe Behrmann]

Hi Andrew,

Am 23.02.04, 00:45 -0800 schrieb Andrew C Mihal:

> Hi,
>     I spent a couple hours this weekend researching this. The fundamental
> paper from Burt & Adelson is here:
>
> http://citeseer.nj.nec.com/burt83multiresolution.html

Can You give an direct link. The above one shows only the
problem(abstract) not the solution (I hope to find it in the full
article).

> I even managed to find an implementation in the (old) Utah Raster Toolkit.
>
> http://www.cs.utah.edu/gdc/projects/urt/help/man1/pyrmask.html
>
> I had to do some hacking to get this tool to run because there seems to
> be a malloc/free bug. I didn't fully fix it - I'm just letting it leak
> memory, it's good enough to test it out. I had to do some ridiculous

Did You prepare makefiles for linux, so some peoples could take a look on
it (me included).

> tiff->pnm->rle conversions to try it but the results were promising.
> I stitched two images with autopano-sift and hugin and ran the result
> through pyrmask. There is no noticable seam in the sky and no noticable
> ghosting in the foreground. I think it's better than what I can do by hand
> in gimp.

Sounds good.

> One downside is that you have to give the pyramid blender a mask to
> identify the transition zone. This paper talks about calculating the mask
> automatically:

The mask is probably the alha channel in the tiff output of
ptstitcher/nona.

> http://www.worldserver.com/turk/computergraphics/pstitcher.pdf
>
> But the authors there don't exactly address the question of how to set the
> mask values at points outside the intersection of the two images. This
> caused some problems that I can elaborate on if anyone is interested.
>
> Is anyone working on this? I think it would be straightforward to update
> pyrmask to work on tiffs directly - the tiff->pnm->rle->pnm chain seems to
> lose the alpha channel. I haven't fully looked into the automatic mask
> creation algorithm yet.

I did some programming with an other approach but leaved it at the moment
due to my time frame. So I would at least like to look at it and do an
test, maybe more.

> Also, has anyone thought of doing some wavelet processing to improve
> sharpness in the overlap region? This is usually on the edge of a frame
> where the focus is not so good. There are some astrophotography image
> stacking programs that do something like this.
>
> Andrew
>
> ---------------------------------
> Andrew Mihal
> www-cad.eecs.berkeley.edu/~mihal
> mihal at eecs.berkeley.edu

Kai-Uwe