Subpixel accuracy

[Radek-5]

Hello,

I have some questions regarding the possibility of having subpixel
accuracy in drawing apps (like GIMP or so).

I'll try to describe the problem the best I can:
Lets say I run GIMP with an image viewed at 25% zoom, that is, one
pixel on display correnponds to 4x4 square on the image. Using the
tablet I draw a curve with a pencil tool (1x1 square brush without
antialiasing). I zoom image to 100% and see that the curve is not
smooth, but consists of short, straight sections either vertical,
horizontal or diagonal, like if it was snapped to 4x4 pixel grid.

I know that this is because GIMP gets the stylus coordinates with
accuracy limited to the resolution of my display. If there was a way to
make it receive (and properly interpret) stylus coordinates with an
increased precision (so that it would be limited by tablet's resolution
rather than display's), it would work as it should.

I've been googling to find a solution for this, but I've only found out
that it's a Xorg limitation and nothing can be done unless Xorg
supports it. Despite that, I think that there can be some workarounds.
One that came to my mind is to create some kind of virtual display with
a size in pixels close to the working area of tablet (so that the
drawing window of GIMP could be sent there), and put it on the
screen zoomed out. What do you think about it? Is it even possible?
I want to say here I'm not a linux guru nor a pro coder, so probably I
coudn't fix it myself.

But this issue is rather important for me, because it feels a little
pointless of having a tablet of a high resolution while not being able
to take any advantage of it.
Or maybe I'm just missing something?

Best regards,
Radek

-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Linuxwacom-discuss mailing list
Linuxwacom-discuss@...
https://lists.sourceforge.net/lists/listinfo/linuxwacom-discuss

[Alexia Death-2]

On Wednesday 23 July 2008 03:03:34 Radek wrote:

> I'll try to describe the problem the best I can:
> Lets say I run GIMP with an image viewed at 25% zoom, that is, one
> pixel on display correnponds to 4x4 square on the image. Using the
> tablet I draw a curve with a pencil tool (1x1 square brush without
> antialiasing). I zoom image to 100% and see that the curve is not
> smooth, but consists of short, straight sections either vertical,
> horizontal or diagonal, like if it was snapped to 4x4 pixel grid.
Please include an image. What you describe right now sounds pretty normal for
a 1x1 not anti-aliased brush.

> I know that this is because GIMP gets the stylus coordinates with
> accuracy limited to the resolution of my display.
Nope, no it does not.  Gimp 2.5 does limit accuracy in some cases tho, for
performance and cutting noise. It is a bit of code that could use some tuning,
and perhaps you are willing to test?

> If there was a way to
> make it receive (and properly interpret) stylus coordinates with an
> increased precision (so that it would be limited by tablet's resolution
> rather than display's), it would work as it should.
Leaving it entrely to tablet is pointless and generates noise, because you
simply aren't able to control you stylus with that precision, but that limit
tho related to display resolution should go unnoticed for the user.
 
> I've been googling to find a solution for this, but I've only found out
> that it's a Xorg limitation and nothing can be done unless Xorg
> supports it.
Xorg supports it. Gimp supports it. Please explain what you expect.

> Or maybe I'm just missing something?
Yep, missing something.

-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Linuxwacom-discuss mailing list
Linuxwacom-discuss@...
https://lists.sourceforge.net/lists/listinfo/linuxwacom-discuss

[David De La Harpe Golden]

2008/7/23 Alexia Death <alexiadeath@...>:

>> I've been googling to find a solution for this, but I've only found out
>> that it's a Xorg limitation and nothing can be done unless Xorg
>> supports it.
> Xorg supports it. Gimp supports it. Please explain what you expect.
>

Well, bearing in mind that some versions of Xorg,  have the device
coordinate rescaling problem, the workaround for which
in linuxwacom drivers significantly reduces tablet resolution.

-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Linuxwacom-discuss mailing list
Linuxwacom-discuss@...
https://lists.sourceforge.net/lists/listinfo/linuxwacom-discuss

[Radek-5]

On Wed, 23 Jul 2008 22:35:19 +0100
"David De La Harpe Golden" <david.delaharpe.golden@...> wrote:
>
> Well, bearing in mind that some versions of Xorg,  have the device
> coordinate rescaling problem, the workaround for which
> in linuxwacom drivers significantly reduces tablet resolution.
>

I'm using Ubuntu Hardy with default Xorg, which has this bug, so at
least I know the source of my problem.

On Wed, 23 Jul 2008 09:31:08 +0300
Alexia Death <alexiadeath@...> wrote:

>
> Xorg supports it. Gimp supports it. Please explain what you expect.
>
> > Or maybe I'm just missing something?
> Yep, missing something.
>

So, Xorg *supports* it, but it's not working. As far as I know, the
whole 1.4 branch of X server is affected, and the fixed version won't
be included in a stable release any time soon. What can I do to make
it work? Do I need to build Xorg unstable from sources?

-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Linuxwacom-discuss mailing list
Linuxwacom-discuss@...
https://lists.sourceforge.net/lists/listinfo/linuxwacom-discuss

[David De La Harpe Golden]

Radek wrote:

> So, Xorg *supports* it, but it's not working. As far as I know, the
> whole 1.4 branch of X server is affected, and the fixed version won't
> be included in a stable release any time soon.


Well, the more gung-ho distros (see: fedora 9) are already shipping 1.5
release candidates*, and there's one in debian/experimental and
ubuntu/intrepid too, but:

Errr. It looks like the xorg xserver 1.4.2 release actually included a
version of Magnus' rescaling fix.  However, the linuxwacom configure
script doesn't know that.  It probably should?

If you're running xorg xserver 1.4.2**, configure linuxwacom with

./configure --disable-quirk-tablet-rescale

and you get hires coords. Though I guess it's possible that there are
other problems with 1.4.x that merit the quirk setting, Magnus and/or
Ping would know better.

* Though there may be new bugs there, of course...
http://lists.freedesktop.org/archives/xorg/2008-July/037528.html
"[xinput] coordinate system of root/x/y" from Thomas Jaeger

** should be able to do an "X -version" at the command line, it outputs
server version and exits rather than trying to open the display.





















































-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Linuxwacom-discuss mailing list
Linuxwacom-discuss@...
https://lists.sourceforge.net/lists/listinfo/linuxwacom-discuss

[David De La Harpe Golden]

David De La Harpe Golden wrote:

> * Though there may be new bugs there, of course...
> http://lists.freedesktop.org/archives/xorg/2008-July/037528.html
> "[xinput] coordinate system of root/x/y" from Thomas Jaeger
>
That should be
"[xinput] coordinate system of root_x/y"



-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
Linuxwacom-discuss mailing list
Linuxwacom-discuss@...
https://lists.sourceforge.net/lists/listinfo/linuxwacom-discuss