Am 05.03.21 um 12:43 schrieb Harry van der Wolf:
Op vr 5 mrt. 2021 om 11:56 schreef 'Kay F. Jahnke' via hugin and other
free panoramic software <[email protected]
<mailto:[email protected]>>:
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:
I did not report anything back and did not do a panorama job, but I did
some "enfusing" jobs on bracket images.brackets of 3 images and brackets
of 5 images.
Using align_image_stack to align them (hand shot images) and let AIS
create a pto.
That's a good way of doing it, and sets reasonable Ev values as well as
doing the registration. Good to batch as well. I tend to collect all
brackets from a take into separate folders (I have a script for that),
then make the PTOs one per folder. After that, a pv batch job (or
several). You can also make HDR-blended images instead of exposure
fusions, by using
--snapshot_extension=exr --blending=hdr
which you can also batch with
--next_after_snapshot=yes
and you may want
--aeb_auto_brightness=yes
for a batch job, because that does a light balance before blending -
especially for JPGs, the brightness values from the PTOs aren't always
optimal.
Then use pv to open the pto and use "U" and "Shift-U" to fuse them.
It's nice to go through the set 'manually' - also to set the shape of
the output.
Shift+U simply takes the first image as output template and renders to
that size and projection. You can actually choose to use any shot of the
bracket as the template, with --snapshot_facet=...
I sometimes use the darkest shot as frame reference - the second, or
number 1 as pv counts from zero, for my canon cameras because it's most
likely to have non-overexposed content all over the frame.
'U' - without shift - is to share the current view, with the shape and
content as the window you see on-screen. Like, you can work with a
square window and fixed 1000X1000 output size and produce frames for you
know what.
I also used these ptos with a complete command-line parameter batch set
(from your Readme), but pv does not exit after the last pto.
Both on the RPi4 and my Linux laptop.
It should, though...
It's nice if you send the actual command line you used if something
unexpected happens - makes it easier for me to figure out if something
is genuinely wrong. But your hint made me look into the logic, and I
actually spotted and fixed a bug here, which seems unrelated, though.
Not the last bug...
I did not report back as I am also a complete newby to pv and first
wanted to explore it a bit deeper.
No problem. Newbies tend to come up with problems that 'experts' would
never manage to produce ;)
Results are good and completely comparable with enfuse.
I take that as a compliment! With the default settings, pv only uses
'exposure_weight' with the standard values for sigma and mu, as proposed
by Mertens, Kautz and Van Reeth, and also the standard in enfuse. enfuse
adds the default of .2 saturation weight, which pv does not (yet)
support. You can vary mu and sigma through command line parameters. I
also added contrast weighting as an experiment (--contrast_weight=...)
which I calculate from the gradient squared magnitude of the b-splines
in the pyramid - the derivative of the splines is easy to get, so this
is quick and precise, but slightly different to standard B&A and enfuse.
I do the GSM separately over the colour channels, and I have the
impression that mixing in a bit of contrast weight (like .2) makes the
result more 'vivid'.
Panos this weekend.
Have fun! And pull and build afresh before you use pv, right now I'm
pushing new stuff frequently.
Kay
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