CVS version: Black background default for PNG

[Philipp K. Janert]

The current CVS version seems to make black the
default background color for the PNG terminal. This
seems to be new behavior - the default used to be
white.

This seems to occur only for PNG, but not for the GIF
or JPG terminals.

I am not sure when this first occurred - the current
CVS version behaves the way as just described, but
the did not do so a few months ago.

I think it would be desirable to have white again be the
background for the PNG terminal (consistent with the
other terminals).

Best,

                Ph.


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[Ethan Merritt]

On Sunday 06 September 2009, Philipp K. Janert wrote:
>
> The current CVS version seems to make black the
> default background color for the PNG terminal. This
> seems to be new behavior

I don't see any such behaviour here.
Please clarify whether this is the libgd png terminal, or the cairo png
terminal.  In either case please also tell us the specific version of
libgd or cairo that gnuplot is linked against.

Also please tell us the precise options of your command
 "set term png ...."


The only related thing that comes to mind is that if you create
a transparent png image, the nominal background (which you don't
actually see because it's transparent :-) is black.  
That is necessary in order to get smooth alpha-blending.

        Ethan

> This seems to occur only for PNG, but not for the GIF
> or JPG terminals
>
> I am not sure when this first occurred - the current
> CVS version behaves the way as just described, but
> the did not do so a few months ago.
>
> I think it would be desirable to have white again be the
> background for the PNG terminal (consistent with the
> other terminals).
>
> Best,
>
> Ph.
>
>
> ------------------------------------------------------------------------------
> Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day
> trial. Simplify your report design, integration and deployment - and focus on
> what you do best, core application coding. Discover what's new with
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>

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[Philipp K. Janert]

Apologies.

I simply used:
        set terminal png
which I assume means the GD terminal.

There have been no changes to my gnuplot
config scripts, that would explain the observed
change in behavior.

Here is the output from ldd (slightly trimmed):
        libgd.so.2 => /usr/lib64/libgd.so.2 (0x00007fd16cf65000)
        libjpeg.so.62 => /usr/lib64/libjpeg.so.62 (0x00007fd16cd41000)
        libfreetype.so.6 => /usr/lib64/libfreetype.so.6 (0x00007fd16cabb000)
        libpng12.so.0 => /usr/lib64/libpng12.so.0 (0x00007fd16c893000)
 (0x00007fd16a9c4000)
        libpangocairo-1.0.so.0 => /usr/lib64/libpangocairo-1.0.so.0
(0x00007fd16a7b8000)
        libpango-1.0.so.0 => /usr/lib64/libpango-1.0.so.0 (0x00007fd16a56e000)
        libcairo.so.2 => /usr/lib64/libcairo.so.2 (0x00007fd16a2f3000)
        libgobject-2.0.so.0 => /usr/lib64/libgobject-2.0.so.0
(0x00007fd16a0ae000)
        libgmodule-2.0.so.0 => /usr/lib64/libgmodule-2.0.so.0
(0x00007fd169eaa000)
        libglib-2.0.so.0 => /usr/lib64/libglib-2.0.so.0 (0x00007fd169be5000)
        libgtk-x11-2.0.so.0 => /usr/lib64/libgtk-x11-2.0.so.0
(0x00007fd169602000)
        libgdk-x11-2.0.so.0 => /usr/lib64/libgdk-x11-2.0.so.0
(0x00007fd169362000)
        libpangoft2-1.0.so.0 => /usr/lib64/libpangoft2-1.0.so.0
(0x00007fd168c9e000)
        libgdk_pixbuf-2.0.so.0 => /usr/lib64/libgdk_pixbuf-2.0.so.0
(0x00007fd168a83000)
        libfontconfig.so.1 => /usr/lib64/libfontconfig.so.1
(0x00007fd168851000)
 
>
> The only related thing that comes to mind is that if you create
> a transparent png image, the nominal background (which you don't
> actually see because it's transparent :-) is black.
> That is necessary in order to get smooth alpha-blending.

I don't think this is it. I have tried it when setting
        set t png notransparent
explicitly and the result is black background, but
when I say
        set t png transparent
the background is not black, but the typical
checkerboard that my image viewer uses for
transparent images.

In other words, I see the black background only
for non-transparent backgrounds.

>
> Ethan
>
> > This seems to occur only for PNG, but not for the GIF
> > or JPG terminals
> >
> > I am not sure when this first occurred - the current
> > CVS version behaves the way as just described, but
> > the did not do so a few months ago.
> >
> > I think it would be desirable to have white again be the
> > background for the PNG terminal (consistent with the
> > other terminals).
> >
> > Best,
> >
> > Ph.
> >
> >
> > -------------------------------------------------------------------------
> >----- Let Crystal Reports handle the reporting - Free Crystal Reports 2008
> > 30-Day trial. Simplify your report design, integration and deployment -
> > and focus on what you do best, core application coding. Discover what's
> > new with Crystal Reports now.  http://p.sf.net/sfu/bobj-july
> > _______________________________________________
> > gnuplot-beta mailing list
> > gnuplot-beta@...
> > https://lists.sourceforge.net/lists/listinfo/gnuplot-beta

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[Ethan Merritt]

On Sunday 06 September 2009, Philipp K. Janert wrote:
>
> Apologies.
>
> I simply used:
> set terminal png
> which I assume means the GD terminal.

Not necessarily, but in your case - yes, since you are linked against libgd.

> There have been no changes to my gnuplot
> config scripts, that would explain the observed
> change in behavior.
>
> Here is the output from ldd (slightly trimmed):
>         libgd.so.2 => /usr/lib64/libgd.so.2 (0x00007fd16cf65000)

Unfortunately, that is non-informative.
Could you please look in wherever-it-is/gd.h to see what the actual
version is?  2.0.35 is common, 2.0.36 is bleeding edge.  

> >
> > The only related thing that comes to mind is that if you create
> > a transparent png image, the nominal background (which you don't
> > actually see because it's transparent :-) is black.
> > That is necessary in order to get smooth alpha-blending.
>
> I don't think this is it. I have tried it when setting
> set t png notransparent
> explicitly and the result is black background, but
> when I say
> set t png transparent
> the background is not black, but the typical
> checkerboard that my image viewer uses for
> transparent images.
>
> In other words, I see the black background only
> for non-transparent backgrounds.

Email me one of these png images so that I can see what it claims to be.

        thanks,

                Ethan

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[Philipp K. Janert]

On Sunday 06 September 2009 02:54:34 pm Ethan Merritt wrote:

> On Sunday 06 September 2009, Philipp K. Janert wrote:
> > Apologies.
> >
> > I simply used:
> > set terminal png
> > which I assume means the GD terminal.
>
> Not necessarily, but in your case - yes, since you are linked against
> libgd.
>
> > There have been no changes to my gnuplot
> > config scripts, that would explain the observed
> > change in behavior.
> >
> > Here is the output from ldd (slightly trimmed):
> >         libgd.so.2 => /usr/lib64/libgd.so.2 (0x00007fd16cf65000)
>
> Unfortunately, that is non-informative.
> Could you please look in wherever-it-is/gd.h to see what the actual
> version is?  2.0.35 is common, 2.0.36 is bleeding edge.

#define GD_VERSION_STRING "2.0.36"

But I have seen different behavior (white default bg)
before with this same GD lib. I have not updated my
Linux install in a year, but have rebuilt gnuplot from
CVS several times since then.

> >
> > In other words, I see the black background only
> > for non-transparent backgrounds.
>
> Email me one of these png images so that I can see what it claims to be.

Will follow outside the mailing list.



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