[ptx] New hugin tutorial - Stitching flat scanned images

[Bruno Postle]

On Thu 31-Mar-2005 at 20:48 -0500, Marek Januszewski wrote:
> 
> 1) Why does it say to optimize v separately for every image except
> the first one (leaving it at 40 degrees - that's actually a
> different question, why leave out the first one)?

The optimiser might decide that it gets a really good fit by
optimising the field of view of all images to zero (which wouldn't
be good).

There is no 'correct' value for the v parameter with a scanned
image, so it is simpler to specify a mid-range number - Probably any
value between 5 and 70 degrees or so would give the same end-result.

> 2) I don't see y and p optimized at for any image - how will the
> images align?

These would add unwanted perspective distortions.  Aligning is done
by using the d & e parameters instead.

> 3) If the pictures were not exactly straight (like scans of map) I
> would setup a horizontal line - for example two points on the same
> line of map to make it straight - the tutorial doesn't mention
> that

I'm trying to keep the tutorial short and to deal with as few new
concepts as possible.

It does suggest using horizontal and vertical control points to
correct the final rotation, but this is a subject for another
tutorial (maybe next year ;-).

> 4) why wasn't autopano used in this example? (it found just couple
> of points for me which is strange, but theoretically should find
> more points on flat image right?)

I did use autopano-sift, but again, I'm trying to keep the tutorial
short and this is a subject for another tutorial.

Actually autopano-sift found lots of control points, but many of
them were near the edge of the scan where the image was distorted.
It would be better to pick just two very well placed manual control
points.

> additionally panorama preview changes field of view in stitcher
> tab (in tutorial 90 and 90), when I click center or fit buttons in
> preview window (I'm not sure if this is a bug?

The centre button changes the yaw of the source images and the
field-of-view of the output to fit - You don't want to change the
yaw as it would add an unwanted perspective distortion.

The fit button changes the field-of-view of the output which is just
what you need.

-- 
Bruno