Introduction
General Quadrilateral Transform is a VirtualDub filter designed to map a quadrilateral
(a region defined by four corners) to another quadrilateral:
Something you will probably want to do more often is more like this :
(very useful when you have filmed something from a wrong angle)
Or like this :
Installing General Quadrilateral Transform
Just copy the "Quadrilateral.vdf" file and the "Quadrilateral Manual" folder in your VirtualDub/plugins directory.
Settings
Well, it's quite simple really: just move the sliders for the X,Y coordinates of each point :)
FAQ (updated Jun 24 2002)
Is General Quadrilateral Transform using bilinear or bicubic interpolation?
Bilinear. There is no real point of using bicubic since in most cases the filter won't be used for
large upsizing. Besides, the algorithm would become so complex it would be terribly slow.
I need the output to be larger than the input to perform my transformation
Just add black borders to the source using another filter before this one.
How can I use General Quadrilateral Transform to do a pure 3D rotation ?
A 3D rotation (or a 2D one, or a flip, etc...) is just a specific case, all you have to do is
to calculate the coordinates of A2 B2 C2 D2 by yourself.
Why is it so slow ?
General Quadrilateral Transform is a general filter, meaning very few optimizations can be done, and the maths behind it
are not THAT easy :)
Is the source code of General Quadrilateral Transform available ?
Not yet. The source code of General Quadrilateral Transform may be released when the filter will have been used and tested by enough people.
In the meantime I don't want people to re-use possibly buggy code.
Using General Quadrilateral Transform with AVISynth
A script sample will be provided soon
History
Jul 17 2003 - Version 0.98 - First public release.
