Have you tried using guides to snap the handles?
--- Leonard Evens <[EMAIL PROTECTED]> wrote:
> I don't see a way to specify the matrix used to perform a desired
> perspective transformation manually. Of course, I can adjust it by
> dragging handles, but it would be much easier for me to calculate what I
> need and then enter the elements of the matrix by hand.
> Needless to say, a typical gimp user would not be able to do this, but I
> am a mathematician who has taught geometry many times during my
> professional life, so I know what to do. I don't need an explanation of
> how the matrix is formed and what it does since I can work that out by
> The gimp manual is not helpful. It refers the reader to the section on
> convolution filters, but that appears to have to do with modifying
> pixels in place rather than moving the pixels---a rather misleading
> reference. Perhaps something entirely different happens if you use the
> full matrix, but the documentation is silent on that matter.
> Of course, I can try to produce what I want by moving the handles, but
> for slight adjustments of large images, that is difficult if not
> impossible. It helps if I increase the magnification enormously, but it
> is still awkward. It would be a lot simpler to be able to enter the
> matrix elements directly.
> Leonard Evens <[EMAIL PROTECTED]>
> Mathematics Department, Northwestern University
> Gimp-user mailing list
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