Re: touchscreen calibration again

Hi Lau,

Thank you very much for proposing your help! You seem to be the right
guy with the right skills for this topic.

I was thinking I could write a C program that some of us could run to
produce the list of points that you need for a thorough analysis.
Actually, the program would first display a grid image on the screen (as
you suggested), and then users would have to press on each grid node in
the right order (say left to right, top to bottom). My program would
output the expected coordinates as well as the measured ones. It
shouldn't be too difficult to code, and not difficult to use either
(though it would perhaps take volunteers 10 minutes to complete).

By the way, Alain, what did you use to harvest your data, but the way?
Reusing your solution may be a good way to do that too...

> Hi
>
> I have been lurking on the list for a while and have been watching the
> amazing progress with admiration. It is really a great work you guys
> have accomplished.
>
> Unfortunately i have not yet had the time to experiment with Linux on
> my own h2200. However on this subject of touch screen calibration, i
> feel that i maybe can contribute something useful. At least i would
> like to give it a try :-)
>
> I work in computer vision, and have some experience with correction of
> nonlinear lens distortion in images. The ts calibration is essentially
> the same problem: A nonlinear mapping from one 2D plane to another. If
> any of you have calibration data i can get, i could load it into
> Matlab, and see if i can build a useable model.

That's a good opportunity to advertise for a free software alternative:
http://www.octave.org/ ;-)

>
> The calibration data should be pairs of corresponding screen and ts
> coordiantes from points distributed over the entire screen. The more
> points the better and at least about 30. Calibration data from several
> different h2200's would be ideal.

What about the format? Would 1 line per point be fine, as follows?
<x actual> <y actual> <x measured> <y measured>

>
> Hopefully it will be possible to build a general model, that can be
> fitted to any h2200 with five points from the end user.

Right! That's what we need to achieve :-) That would also be great if
the methology (and hopefully driver code) could be reused for other
devices...

>
> I do not know what the simplest way of creating such a data set is.
> But it should be possible to either create an extended version of the
> standard 5 point calibration aplication, or to just to load a full
> screen bitmap with premade points, and click them all in order. I
> would love to do this myself, but i do not have the time at the moment
> :-(, But if any of you can create the data set, i should have the time
> to try to create the model.

Great!

    Cheers,
   
    Michael.

-- 
Michael Opdenacker
http://opdenacker.org/