On Sat, Mar 15, 2008 at 9:33 AM, Leonard Evens <[EMAIL PROTECTED]> wrote: > To review, my basic aim is to produce very precise perspective > transformations in order to merge panoramas which involve very large > images. Is there some reason you are not using hugin, which is a very capable panorama stitching software? http://en.wikipedia.org/wiki/Hugin_%28software%29
> Unfortunately, there seems to be no way to specify target > points except by dragging, but even given that, there is an additional > problem. Typically, I have a facade in which the top and bottom may > not be exactly parallel. In order to get them that way, I need to move > corners on top and bottom of the building to desired positions. I can > move the top corner more or less to where I want it. But when I try to > move the bottom corner where I want it, I end up moving the top corner. > (The only exception is when the original top was actually at the upper > handle on that side. In that case, it stays at the new position when > the bottom is moved.) If Igo back to correct the top, the bottom > moves. You can iterate this process until you get it about right, which > works well for moderate sized images, but for large images and precise > positioning, it takes quite a while and is very frustrating. > > I've investigated the mathematics behind this, which involves projective > geometry and cross ratios. Using that, I can determine where I have to > move the upper and lower handles to get points in between to go where I > want them to go. That would work, but the formulas are pretty involved > and cumbersome to apply. I experimented with using selections, but that > doesn't work because what is outside the selection is not moved and so > lines can be bent. > > I don't see any other way to accomplish what I want except successive > approximations or using the formulas. Can anyone suggest an alternate > approach? > > -- > Leonard Evens <[EMAIL PROTECTED]> > Mathematics Department, Northwestern University > > _______________________________________________ > Gimp-user mailing list > Gimp-user@lists.XCF.Berkeley.EDU > https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user > _______________________________________________ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
