Re: CVS version: Black background default for PNG

[Ethan M. <merritt@u.washington.edu>]

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