On 16 Feb., 18:56, Dan <[email protected]> wrote:
> sorry,,i forgot to mention that I was talking about forward transform
> and the image was the source image. and most of time they do inverse
> transform. I just went for forward just to understand. It should work
> atleast (even if it leaves some pixels blank, thats not the concern
> right now), I dont want to go for interpolation. Thing is just it
> should work, quality i will check later on. I was reading the source
> code of libpano and stuck again. Can you tell me what these lines are
> doing in math.c of libpano library ?
>
> what is sphere_tp_erect doing?
sphere_to_erect converts from spherical coordinates to equirectangular
projection, says it's name - and that's about all I know.
> and these lines in it? ::
> phi = x_dest / distanceparam;
> theta = - y_dest / distanceparam + PI / 2;
> if(theta < 0)
> {
> theta = - theta;
> phi += PI;
> }
> if(theta > PI)
> {
> theta = PI - (theta - PI);
> phi += PI;
> }
>
> s = sin( theta );
> v[0] = s * sin( phi ); // y' -> x // sin(theta)*sin(phi)
> v[1] = cos( theta ); // z' -> y //
> cos(theta)
>
> r = sqrt( v[1]*v[1] + v[0]*v[0]);
> theta = distanceparam * atan2( r , s * cos( phi ) );
>
> *x_src = theta * v[0] / r;
> *y_src = theta * v[1] / r;
... I fear you'll have to figure it out yourself. I suppose it's
reasonably sraightforword trigonometry, but I haven't looked into the
details - I'm more interested in using the transforms than
understanding their inner workings, so I can't really help you there.
> Where do these formulas come from? Isn't there atleast some
> documentation of this libpano anywhere ???
you'll have to do some research. Try
http://wiki.panotools.org/Projection
for starters and see where it takes you. It's a complex topic. Trying
to figure out libpano isn't for the fainthearted. If you want it
simple and well-documented, this is probably not where you want to
look. Best of luck
Kay
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