To review, my basic aim is to produce very precise perspective transformations in order to merge panoramas which involve very large images. 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