The Grumpy Editor's hugin experience [LWN.net]

The Grumpy Editor's hugin experience

Posted Sep 9, 2009 0:04 UTC (Wed) by aigarius (subscriber, #7329)
Parent article: The Grumpy Editor's hugin experience

As the author of several Debconf group photos I have two pet pieves with hugin (along with the ones the editor already highlighted):
* Hugin has a tendency to twist faces into ugly shapes. Take a group photo of 5x5 images and have a person be near the corner in several images. There is a good chance that such a person will end up with half a face from one photo, third of a face from another photo and a small corner above the left eye from another photo resulting in a convulsed and twisted face, distorted beyond recognition. People moving and turning their heads ever so slightly complicates this even further. Face detection technologies could help here.
* The way that I usually try to fix the above bug is to take the final photo and paste over faces for the unlucky people - I cut from transformed but unmerged images over the final rendering. This would have been much easier if hugin could have allowed some sort of editable export option like a layered GIMP file where I would be able to adjust the blending.

Oh, and it creates temp files in /tmp regardless of the configuration setting, so be sure to have enough RAM for really large panoramas like the 98Mpix Debconf 9 group photo I made with hugin earlier this year ;)

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Controlling face overlays from different photos

Posted Sep 9, 2009 3:35 UTC (Wed) by hannada (subscriber, #4633) [Link]

Hugin does provide a fairly simple mechanism for controlling situations such as the one you describe (where different pieces of images of faces are inappropriately combined from different images). This method requires that the images be in a format that provides an alpha channel to control transparency. In my case, I

1) Converted the original images from JPEG into PNG. (JPEG seems not to support alpha channels).
2) Used GIMP to activate an alpha channel layer for the image.
3) Used GIMP to "paint" the alpha channel layer "off" (fully transparent) for the parts of the input images that I wished to exclude from the final merged image.
4) Export the modified image as a PNG file (large, but temporary), then built the final panorama from these modified images.

In this way, I was able to select which of the redundant image elements would be excluded and eliminate the "chopped image" appearance that you describe. Note that this feature is strictly "on" or "off". Gradations in the alpha channel are ignored.

Controlling face overlays from different photos

Posted Sep 10, 2009 20:47 UTC (Thu) by roelofs (guest, #2599) [Link]

1) Converted the original images from JPEG into PNG. (JPEG seems not to support alpha channels).

JPEG/JFIF doesn't, but JPEG/JNG does (e.g., see libmng). It's not widely supported, though.

However, for what you're doing--multistage image editing--you want PNG or some other lossless format anyway. Switch back to JPEG only at the very end.

Greg