"Hidden" PNG data - is there a way to remove it?

[Roots]

It came to my attention recently that somehow, there is somehow
"hidden" data in several of our .PNG images that have been created and
edited with a variety of different programs (GIMP, Photoshop, and
others). However one of the artists we have working on our project now
uses this application, and he pointed out that many of our images
have a lot of extra image data, that make those images un-workable in
GrafX2, because the transparent regions are filled with all this data.

Here's an example to show what I mean:
http://www.allacrost.org/staff/user/roots/art/wooden_counters.png

Try opening that up in your web browser. Then compare that after
opening it with GrafX2. You'll see a lot of extra images in the
regions that are covered in transparency.


While its nice to know that this hidden data is there, every other
image editor we've ever used has not displayed this data, and right
now our artist using your application can't really make any
modifications to these types of files because all this hidden data is
really screwy. I checked your FAQ and the only thing that vaguely
remarks on this hidden data is this:

http://code.google.com/p/grafx2/wiki/FAQ#Q:_Why_aren%27t_the_hidden_parts_of_the_picture_filled_when_I


So my question is: is there an option in GrafX2 where you can choose
not to show this hidden image data? Its impractical for us to tell
people not to use GrafX2 or to tell them to only use GrafX2 because we
want people to use whatever tool they are comfortable with. So GrafX2
needs to co-exist with other editor applications. Thanks

[pulko...@pulkomandy.ath.cx]

On 2011-07-08 at 18:57:16 [+0000], Roots <roots...@gmail.com> wrote:
> It came to my attention recently that somehow, there is somehow
> "hidden" data in several of our .PNG images that have been created and
> edited with a variety of different programs (GIMP, Photoshop, and
> others). However one of the artists we have working on our project now
> uses this application, and he pointed out that many of our images
> have a lot of extra image data, that make those images un-workable in
> GrafX2, because the transparent regions are filled with all this data.
>
> Here's an example to show what I mean:
> http://www.allacrost.org/staff/user/roots/art/wooden_counters.png
>
> Try opening that up in your web browser. Then compare that after
> opening it with GrafX2. You'll see a lot of extra images in the
> regions that are covered in transparency.
>

This is because GrafX2 simply doesn't handle the alpha channel in PNG pictures properly.
Saving the picture in a palette-based format (for example with GIMP use color > mode > indexed, then
save the file again) will allow GrafX2 to read the file properly. when saving as PNG, GIMP also allows
you to uncheck "keep color values for transparent pixels".
Doing these two things will get your file smaller, and with no loss.

This is already registered in our bugtracker :
http://code.google.com/p/grafx2/issues/detail?id=358

>
> While its nice to know that this hidden data is there, every other
> image editor we've ever used has not displayed this data, and right
> now our artist using your application can't really make any
> modifications to these types of files because all this hidden data is
> really screwy. I checked your FAQ and the only thing that vaguely
> remarks on this hidden data is this:
>
> http://code.google.com/p/grafx2/wiki/FAQ#Q:_Why_aren%27t_the_hidden_parts_of_the_picture_filled_when_I

This is not related.

>
>
> So my question is: is there an option in GrafX2 where you can choose
> not to show this hidden image data? Its impractical for us to tell
> people not to use GrafX2 or to tell them to only use GrafX2 because we
> want people to use whatever tool they are comfortable with. So GrafX2
> needs to co-exist with other editor applications. Thanks

Convert the image using another tool first, and it will work fine in GrafX2. Keep in mind GrafX2 is a
program to work with indexed pictures, not truecolor ones.

See what I mean :
http://pulkomandy.lexinfo.fr/drop/wooden_counters_256.png will open fine in GrafX2. It's 27K instead of
135.

We'll try to get the issue fixed in the next release,but at least you can get around it.

Thanks for using GrafX2 !
Is this for a game ? We'd like to add a link to it somewhere in our pages :)

--
Adrien / PulkoMandy
GrafX2 project team

[Roots]

Thanks for the quick and thorough reply, that answers everything I
need to know. Yes, this is for a game. Its been in production for
several years as a free and open source project. If you'd like to add
a link to it, I have no problem with that at all. Thanks again!


Hero of Allacrost
http://www.allacrost.org
2D role-playing game




On Jul 8, 5:21 pm, pulkoma...@pulkomandy.ath.cx wrote:

> >http://code.google.com/p/grafx2/wiki/FAQ#Q:_Why_aren%27t_the_hidden_p...

>
> This is not related.
>
>
>
> > So my question is: is there an option in GrafX2 where you can choose
> > not to show this hidden image data? Its impractical for us to tell
> > people not to use GrafX2 or to tell them to only use GrafX2 because we
> > want people to use whatever tool they are comfortable with. So GrafX2
> > needs to co-exist with other editor applications. Thanks
>
> Convert the image using another tool first, and it will work fine in GrafX2. Keep in mind GrafX2 is a
> program to work with indexed pictures, not truecolor ones.
>

> See what I mean :http://pulkomandy.lexinfo.fr/drop/wooden_counters_256.pngwill open fine in GrafX2. It's 27K instead of