Few control points on HDR images with CPFind

[Torsten Stremlau]

I recently started using Hugin to create 360° panoramas of HDR images.
The images I am trying to stitch together are in OpenEXR format.

I noticed that cpfind hardly finds any control points on these HDR images.
If I convert the images to LDR first, then cpfind actually finds quite a few control points.

I poked around in cpfind and found out that this is probably because the HDR images are first mapped
to [0,255] before any features are detected. As this is done using a linear mapping the images end up being
mostly black with only the brightest parts in the image visible. (Usually the sun...)

When I switched the mapping in cpfind to logarithmic in the source code, the results became much better and
more control points were found.

Is this a known issue, or am I doing something wrong?

I am using hugin on ubuntu 16.04 64bit.
I built hugin myself from hg revision:674a88cfacb6468ac185c8e12392ba9c206a7113

-- Torsten

[T. Modes]

Hi Torsten,

Am Mittwoch, 8. Juni 2016 00:15:55 UTC+2 schrieb Torsten Stremlau:

When I switched the mapping in cpfind to logarithmic in the source code, the results became much better and
more control points were found.

Is this a known issue, or am I doing something wrong?

The hdr capabilities of cpfind has not been extensively tested. So it may be that there are some bugs.
Can you provide a patch of your changes?

Thomas

[Torsten Stremlau]

Hi Thomas,

here is the patch of the changes I made.

-- Torsten

Am Mittwoch, 8. Juni 2016 00:15:55 UTC+2 schrieb Torsten Stremlau:

[T. Modes]

Hi Torsten,

Am Mittwoch, 8. Juni 2016 19:02:14 UTC+2 schrieb Torsten Stremlau:

here is the patch of the changes I made.

I think it is reasonable to activate the logarithm mapping for all hdr images (currently filetype double/float and linear response type) automatically instead of an additional switch.
So I committed this modification. I hope this works for you also.

Thomas

[Torsten Stremlau]

Hi Thomas,

Am Mittwoch, 8. Juni 2016 20:28:17 UTC+2 schrieb T. Modes:

I think it is reasonable to activate the logarithm mapping for all hdr images (currently filetype double/float and linear response type) automatically instead of an additional switch.
So I committed this modification. I hope this works for you also.

Works nicely, thank you very much :)


-- Torsten

[David W. Jones]

Do 16-bit TIFF files count as HDR for this? Or is it just EXR? I use
TIFF, not EXR.

Thanks.

--
David W. Jones
gnome...@gmail.com
wandering the landscape of god
http://dancingtreefrog.com

[T. Modes]

Am Donnerstag, 9. Juni 2016 09:10:32 UTC+2 schrieb GnomeNomad:

> images (currently filetype double/float and linear response type)

Do 16-bit TIFF files count as HDR for this? Or is it just EXR? I use
TIFF, not EXR.

It pays to be able to read.
Again for you "currently filetype double/float and linear response type"

Second, are there problems with less or no control points in your images?

[Gnome Nomad]

Sorry, I did read it, then had to translate from programmerese. ;)
I have no problems getting control points in 16-bit TIFFs. I've never tried an EXR as input to Hugin. I sometimes use them as output for use in Luminance HDR, but that's not dealing with control points.