post-process photos of flat rectangular objects to removeperspective

On Jul 19, 3:12*am, Poldie <_.@._> wrote:
> Hugo Trebl wrote:

> > I am searching for a tool that allows quick post-processing to remove
> > the distortion introduced by the perspective, and to discard
> > unnecesary background. In the end the object should be aligned with
> > the picture borders and fill the whole picture

> > Is there any tool good for this sort of task?
>
> You can do it manually using the free Windows app `PAINT.net`:
>
> http://www.getpaint.net/doc/latest/en/RotateZoom.html

Wow, that is impressive.
It looked to be exactly what I need: powerful transformation options,
but no way to end up with an incorrect perspective

Unfortunately it seems that optical perspective does not work
backwards:
If I rotate a rectangular shape with paint.net's perspective tool
along the z axis, and then try to inverse this transformation, it does
not work. No matter which parameters I choose, I cannot get the
rectangular shape back.

I probably need some sort of "inverse perspective" transformation tool
to reverse perspective.
Can anyone confirm that?
Does this sort of transformation have a name?

On Jul 19, 12:38*pm, Hugo Trebl <singal...@dodgeit.com> wrote:

> Unfortunately it seems that optical perspective does not work
> backwards:
> If I rotate a rectangular shape with paint.net's perspective tool
> along the z axis, and then try to inverse this transformation, it does
> not work. No matter which parameters I choose, I cannot get the
> rectangular shape back.
>
> I probably need some sort of "inverse perspective" transformation tool
> to reverse perspective.
> Can anyone confirm that?
> Does this sort of transformation have a name?

Apparently this sort of transformation is aptly named "Inverse
Perspective Mapping" (IPM), who would have thought that?
http://www.argo.ce.unipr.it/argo/eng...chdet/ipm.html