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image alignment/registration

Casey Connor-2
Hi - I was curious what the best overall image alignment plugin/method
in GIMP (or out of GIMP) was these days?

"Best" for me means "most powerful/flexible/option-rich".

I've come across the hugin align_image_stack, the G'MIC plugin's "Align
layers" option, and the image registration plugin
<http://gimp-image-reg.sourceforge.net/>. (I've also used the "Exact
Aligner" script, but it's two layers only.)

The goal is to align and then use mean/median for noise reduction
stacking. I'll probably be working in 16bit.

Do all three methods do sub-pixel alignment? I read someone on pixls.us
suggesting that the user upscale the source images by up to 1.33x before
aligning for the sake of effectively achieving sub-pixel alignment, but
if the current alignment methods do that anyway, seems like I should
skip it... ?

Thanks!

-c


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Re: image alignment/registration

Pat David
Align_image_stack is usually the best option other than possibly attempting
it manually directly in Hugin.
On Sat, Feb 4, 2017 at 8:57 PM Casey Connor <[hidden email]>
wrote:

> Hi - I was curious what the best overall image alignment plugin/method
> in GIMP (or out of GIMP) was these days?
>
> "Best" for me means "most powerful/flexible/option-rich".
>
> I've come across the hugin align_image_stack, the G'MIC plugin's "Align
> layers" option, and the image registration plugin
> <http://gimp-image-reg.sourceforge.net/>. (I've also used the "Exact
> Aligner" script, but it's two layers only.)
>
> The goal is to align and then use mean/median for noise reduction
> stacking. I'll probably be working in 16bit.
>
> Do all three methods do sub-pixel alignment? I read someone on pixls.us
> suggesting that the user upscale the source images by up to 1.33x before
> aligning for the sake of effectively achieving sub-pixel alignment, but
> if the current alignment methods do that anyway, seems like I should
> skip it... ?
>
> Thanks!
>
> -c
>
>
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image alignment/registration

oneaty
>Align_image_stack is usually the best option other than possibly
>attempting
>it manually directly in Hugin.
>On Sat, Feb 4, 2017 at 8:57 PM Casey Connor
><[hidden email]>
>wrote:
I tried align_image_stack many times, using different options combinations, but
coudn't get aligned images in the end.
I'm trying to abandon PS and fully use gnu software, but, so far, couldn't find
a decent replacent for PS's autoalign feature.
The point is that I didn't use tripod, so there are alignment differences in the
original frames. PS's autoalign can handle that situation in a very satisfactory
manner.
Am I missing something?
I don't want to piggyback Casey's post, but since I have the same question, I
choose to put this post here.
If admins feel I should open another thread, just let me know.



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Re: image alignment/registration

Casey Connor-2
> I tried align_image_stack many times, using different options combinations, but
> coudn't get aligned images in the end.

Per recommendations here, I've used it and it worked really well; I've
read, and experienced, that it seems to need images to be pretty close
already. Meaning, by default it won't assume the images should be
aligned a great distance, so if you moved much while shooting it might
not work out. You might investigate the -g option -- I'm not totally
clear on how it works, but it sounds from the description like it might
change the scale which align_image_stack uses to find control points.
Maybe also the -t option?

You could also check out hugin, which AFAIK uses align_image_stack under
the hood to do its alignment. It allows all kinds of manual
intervention/editing of control points. I understand that a "one-click"
solution is ideal, but mention it just in case. You can at least
visually see what's happening with the control points and understand
better where things are going wrong.

-c

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image alignment/registration

oneaty
>Per recommendations here, I've used it and it worked really well; I've
>read, and experienced, that it seems to need images to be pretty close

Thanks for the feedback.
I believe if I shoot with a tripod it would work fine.
The point is that a tripod isn't an option to me most of the time.
My only camera is an old point & shoot Canon A3100, boosted by CHDK. CHDK has
many wonderful features, but the one I mostly use is its raw capability, not
available on Canon original  firmware.
Besides, I usually do a lot of stacking, pushing the final image quality to its
limits.
And here is my problem.
With PS, I can auto align hand held shots with excellent results. The
differences in perspective between shots do exist but are not big, because I try
to hold the camera the most steadier I can when shooting.
I just came from aligning the same set of pictures in PS I tried in Hugin, and
it worked almost perfectly.
Before that, I had also tried using JImage (and its full package FiJi), but it
is really, really complex and I gave up.
So, unfortunately (being an open source fan), I will still have to keep with PS,
until I find an open source alternative to its auto alignment feature.


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Re: image alignment/registration

Casey Connor-2
Did you try the -g option with align_image_stack? Or -t?

I align hand-held images with align_image_stack and it works fine, even
without those options... e.g. this one:
https://www.flickr.com/photos/lacinato/32628735771/in/dateposted-public/

-c

On 03/24/2017 12:58 PM, oneaty wrote:

>> Per recommendations here, I've used it and it worked really well; I've
>> read, and experienced, that it seems to need images to be pretty close
> Thanks for the feedback.
> I believe if I shoot with a tripod it would work fine.
> The point is that a tripod isn't an option to me most of the time.
> My only camera is an old point & shoot Canon A3100, boosted by CHDK. CHDK has
> many wonderful features, but the one I mostly use is its raw capability, not
> available on Canon original  firmware.
> Besides, I usually do a lot of stacking, pushing the final image quality to its
> limits.
> And here is my problem.
> With PS, I can auto align hand held shots with excellent results. The
> differences in perspective between shots do exist but are not big, because I try
> to hold the camera the most steadier I can when shooting.
> I just came from aligning the same set of pictures in PS I tried in Hugin, and
> it worked almost perfectly.
> Before that, I had also tried using JImage (and its full package FiJi), but it
> is really, really complex and I gave up.
> So, unfortunately (being an open source fan), I will still have to keep with PS,
> until I find an open source alternative to its auto alignment feature.
>
>

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image alignment/registration

oneaty
>Did you try the -g option with align_image_stack? Or -t?
>
>I align hand-held images with align_image_stack and it works fine,
>even
>without those options... e.g. this one:
>https://www.flickr.com/photos/lacinato/32628735771/in/dateposted-public/
>
>-c

Tried

align_image_stack -a *.tif

and

align_image_stack -a -g *.tif

and no success...

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image alignment/registration

oneaty
>Tried
>
>align_image_stack -a *.tif
>
>and
>
>align_image_stack -a -g *.tif
>
>and no success...

The whole process:

1 - Shoot in DNG
2 - RawTherappe - Open dng's with preset Neutral and save them as tif
3 - align_image_stack.

Btw, beautiful image.

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Re: image alignment/registration

Casey Connor-2
In reply to this post by oneaty
So, backing up a step: when you say align_image_stack doesn't work, what
do you mean exactly? I assumed you meant that it did a poor job aligning
the images, but I don't think the command lines you list there would
even work to start the program, so I'm wondering now if you meant that
it doesn't even run?

"-a" requires a prefix following it, and "-g" requires a number.

E.g.:

align_image_stack -a someprefix -g 8 *.tif

Documentation is here: http://wiki.panotools.org/Align_image_stack

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image alignment/registration

oneaty
>So, backing up a step: when you say align_image_stack doesn't work,
>what
>do you mean exactly? I assumed you meant that it did a poor job
>aligning
>the images,

Correct assumption,


but I don't think the command lines you list there would

>even work to start the program, so I'm wondering now if you meant that
>it doesn't even run?
>
>"-a" requires a prefix following it, and "-g" requires a number.
>
>E.g.:
>
>align_image_stack -a someprefix -g 8 *.tif
>
>Documentation is here: http://wiki.panotools.org/Align_image_stack

Well, it works.

-a without explicit prefix defaults to the name of the first image file given.

-g without explicit number defaults to 5 (that is written in the --help option)

Btw, what os are you using?

I'm running this on Linux (Ubuntu 16.04)

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Re: image alignment/registration

Casey Connor-2
Ah, ok. So what exactly goes wrong: one or two of the images is off-kilter?

If you specify -g, try using something besides the default, as I'm not
sure that using the default will change the behavior. (Meaning, not
specifying -g probably results in the same thing as just "-g" -- the
documentation is a little unclear, but I assume it's active when not
specified.) Perhaps try -g 3 or 4 instead? I'm not 100% sure how to
interpret it. If that doesn't work, try 6 or 7?

> Btw, what os are you using?

Kubuntu 16.10.

-c

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image alignment/registration

oneaty
>Ah, ok. So what exactly goes wrong: one or two of the images is
>off-kilter?

Yes, that's it. I'm just checking the first two images, since PS successfully
aligned all of them.

>
>If you specify -g, try using something besides the default, as I'm not
>sure that using the default will change the behavior. (Meaning, not
>specifying -g probably results in the same thing as just "-g" -- the
>documentation is a little unclear, but I assume it's active when not
>specified.) Perhaps try -g 3 or 4 instead? I'm not 100% sure how to
>interpret it. If that doesn't work, try 6 or 7?
>Kubuntu 16.10.
>
>-c

I tried

align_image_stack -a align -g 10 -t 5 *.tif

and

align_image_stack -a -dixyz *.tif

and

align_image_stack -a align -SAP *.tif

and the images (the first two) are still unaligned

The resulting stack by using Photoshop can be seen here https://flic.kr/p/SDKdBf

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Re: image alignment/registration

Casey Connor-2

> I tried
>
> align_image_stack -a align -g 10 -t 5 *.tif

Did you try with a lower-than-default -g? E.g. "-g 3"?

If you want to upload the base .tif files somewhere, I can try to align
them, so we can see if there is some strange difference between
align_image_stack on our machines.

-c

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image alignment/registration

oneaty
>Did you try with a lower-than-default -g? E.g. "-g 3"?
>
>If you want to upload the base .tif files somewhere, I can try to
>align
>them, so we can see if there is some strange difference between
>align_image_stack on our machines.
>
>-c
Hey, thanks for that!

Follows Flickr album https://flic.kr/s/aHskT2xjh1

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image alignment/registration

oneaty
>Hey, thanks for that!
>
>Follows Flickr album https://flic.kr/s/aHskT2xjh1

EDIT: I noticed that Flickr automatically changed the tiffs I uploaded into
jpgs, so I wanted to make sure it wouldn't be a waste of time to you.
I did what I suppose you'll do:
1 - Downloaded Flickr album
2 - Aligned the images with align_image_stack
3 - Opened the output from previous step as layers in Gimp.
4 - Changed layers opacity according to the mean rule (100%, 50%, 33%...)
4 - Did the same on PS

Conclusion: The format change didn't interfere in the original alignment issue:
PS correctly auto-aligned the layers, but align_image_stack didn't.

The following images are screen shots from both ps and gimp showing the final
stacks: http://imgur.com/a/drKdB

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