On Fri, Oct 17, 2014 at 02:09:49PM -0700, Nicholas Robbins wrote: > > On Friday, October 17, 2014 2:30 PM, Nicholas Robbins > > <[email protected]> wrote: > > > > <snip actual request> > > > > Ok, it seems like this should be easier. If we had a filter that did the > > same > > thing as vf_perspective but with inverse options this would be easy. So > > instead > > telling it what points you want to send to the corners, you tell it where > > you > > want the corners sent. > > > > I ran the math and the formulas to map between the two different ways of > > specifying the projective transformation are a bit messy. For instance, if > > you > > want to send the corners to x0:y0:x1:y1:x2:y2:x3:y3 the first option for > > the > > vf_perspective should be > > > <snip messy formula> > > > > not something you can put on the command line or even want to work out by > > hand. > > However, it would be totally doable to calculate in filter initialization. > > > > So is it possible to make a filter that is basically just a wrapper around > > another filter? This hypothetical filter (call it vf_keystone) would just > > call > > vf_perspective with crazy options. Clearly I could just copy the > > vf_perspective > > filter and then insert these changes, but than any future changes to > > vf_perspective wouldn't filter down to vf_keystone. > > > > Is this possible? > > > > -Nick > > Upon further thought and a closer read of the vf_perspective code, I think an > easier option would be to insert an option of "sense" or "mode" or something. > Then condition the code at lines 144-160 (these lines calculate the matrix > used for the transformation) and then put in another block conditioned on the > "mode" that finds the inverse matrix rather than the matrix currently found. > > Is this a reasonable approach? If so, I think I'll put this in in a little > while.
yes, thats an option too [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB No human being will ever know the Truth, for even if they happen to say it by chance, they would not even known they had done so. -- Xenophanes
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