In a way I'm surprised that so far nobody has actually reported doing
what I propose in this thread, namely performing a stitching job or
exposure fusion, using pv's adapted Burt & Adelson image splining
algorithm. I admit my documentation isn't so easy to access on this
topic, so here's a brief how-to:
First, you need a PTO file. pv only processes a subset of possible PTO
content, and the stitching algorithm has some limitations, so:
- your images should (for now) not have an alpha channel.
- source images should be rectilinear, spherical, cylindric,
stereographic or fisheye.
- the PTO's 'p-line' is ignored, you may set the output projection with
a command-line parameter.
- masks are also ignored.
- for this trial, please use sRGB input (like, JPGs or PNGs) or EXR.
I recommend you work from the command line with pv in windowed mode, so
you can see what pv echos. Let' say your PTO is called 'pano.pto'. try
this: (I'll explain the parameters afterwards)
./pv -W --feathering=10 --target_projection=spherical \
--snapshot_magnification=4 --window_width=1000 \
--window_height=500 pano.pto
You'll see pv's 'live stitch' - a 'quick' stitch which only uses slight
feathering between the facets.
Now use the arrow keys and the zoom keys - or mouse gestures - to show
in the viewer window what will later be in your stitched panorama. Tip:
if you lose the horizon, press 'L' for 'level'. There is no view
cropping in pv. 'Empty' space shows black, which is no problem. If the
aspect ratio is not right, just reshape the window. pv is wysiwig, so
the output will have the same size as the window.
If the brightness values of the images don't seem to fit well, press
'Shift + L' to do an automatic brightness balance - don't worry about
slight differences after that.
Now press 'P'. pv will now stitch the panorama in the background - you
could carry on viewing or making more snapshots etc. - you just can't
'leave' the current image (set) until all snapshots, stitching jobs etc
which depend on it are done. For now, you may just press 'escape', pv
will terminate once the stitch is ready.
From the command line, you can see to which filename the stitch was
saved. Try and open it in pv to convince yourself that the stitch has in
fact happened - it should look much better than the 'live stitch' and be
close to what you are used to from using enblend.
Here is the explanation of the parameters:
-W run pv in a window, not in fullscreen mode
--feathering=10 use a bit of feathering at the facet borders and for the
stitching masks
--target_projection=spherical view and create output in spherical projection
--snapshot_magnification=4 make the output 4X as large as the viewer window
--window_width=1000 viewer window's height
--window_height=500 viewer window's width
pano.pto your PTO file
So you see, stitching with pv is no rocket science, and you can take it
from there! To do an exposure fusion, let's suppose you have the
registered bracket in 'bracket.pto'. Try this:
./pv -W --next_after_fusion=yes --snapshot_like_source=yes bracket.pto
You'll see a viewer window while pv does a batch job, and when the job
is done the window closes:
--next_after_fusion=yes behaves as if you had pressed first 'U' then
'Tab' - so it launches the exposure fusion, then proceeds to the next
image - or terminates, since there is no next image.
--snapshot_like_source=yes creates output which has the same size and
projection as the input
That's just to give you a taste for pv's batch mode, which you can in
fact use to batch-process entire collections of PTOs and images,
stitching, fusing, HDR-merging or snapshotting along the way to your
heart's content ;)
Enjoy
Kay
--
A list of frequently asked questions is available at:
http://wiki.panotools.org/Hugin_FAQ
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