On 13 Feb., 11:13, Jeffrey Martin <360cit...@gmail.com> wrote: > I was thinking also... > > for panos, the centers of images usually do not overlap. > isn't searching the WHOLE of images a big waste?
It seems wasteful, but you also have to consider the time you have to invest to pre-position the images roughly so the ROI can be detected as roughly that area where the pre-aligned images overlap - and the time it takes to extract/mask the ROI. Scanning the whole image assures that the images can be positioned and oriented in any way and all overlaps will be found. There is another aspect which becomes more important with fisheyes and stereographic images: if you feed the CPG with a partial image, it can't decipher the warp to adapt it's feature point detector: the image geometry is quite different from center to margin. So you can't just use partial images, but you have to use the whole images and mask them appropriately. Masking means introduction of additional data into the process, either in the shape of a separate mask or as an alpha channel. Using an alpha channel might be a reasonalbly inexpensive and transparent (hah) way of doing the needful, but I'm not sure if the current CPGs honour alpha channels - I rather doubt it. Finally, if you use a reasonable overlap of 30% and calculate how much of your images is left over in areas which are not overlapping, you may find out that these areas are quite small after all, since the overlap is on all margins. Even with 25% overlap, much less than half of the image is outside overlaps. If you take all of this into account, I think the gain is not worth the effort for everyday work. On the other hand, there may be special situations where the savings would be significant. To cater for these, the mechanism of limiting the scan for feature points to a ROI should be available as an optional feature. In fact, this sounds like an ideal scenario for a plugin. I'd expect stuff like this to be among the first things to be implemented as a plugin as soon as the plugin facility becomes maintream (currently verification of the implemented mechanism on Mac OS is pending, but I hope it won't be too much longer). I am currently toying with this mechanism for use in another demo plugin, but I want to throw in rewarping of the parts of the images that correspond to the ROIs to a common projection to make them geometrically as similar as possible, thus improving CPG performance especially with fisheye images and avoiding warp-related CPG problems - some sort of high-end matching which would produce very good quality, well-distributed CPs, particularly for applications like lens calibration. Also, it would be nice to get quick access to the warped partial images for visual inspection. To put a final tag on it - nice to have, but not crucial. Kay -- You received this message because you are subscribed to the Google Groups "Hugin and other free panoramic software" group. A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ To post to this group, send email to hugin-ptx@googlegroups.com To unsubscribe from this group, send email to hugin-ptx+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/hugin-ptx
