Anti-Aliasing and transparency issues

[Peter Lu]

Hey, I'm fairly new to pyglet and opengl, less so to python.

I'm trying to load a 320x240 png with transparency and stretching it
to fill the entire screen in full screen mode. I'm encountering two
issues. When transparency is working properly, I get a nice clean un
anti-aliased edge when I don't scale the image. When I do scale the
image, there is this ugly white line between the transparent and
opaque parts of my image. Considering most of the screen is black,
this white line is VERY noticeable and absolutely must be fixed. The
image I am trying to draw has no anti-aliasing to speak of and only
has two colors in it, black and transparent.

Less importantly, the gnome image viewer clearly shows that all my
pngs have transparencies in them but curiously enough, only one of 9
images gets drawn with transparency. All my images are exported
simultaneously from graphicsgale. Right before drawing each time I am
calling:

glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)

I did this as a test without any of my other code running to eliminate
any other possible issues and I have the same problem. Transparency
only works properly on one of the 8 images so it must be something
with the files but I'm hoping there is some gl setting that I don't
know about that accounts for different alpha settings.

Despite these issues, I'm loving pyglet. Any help would be much
appreciated.

[claudio canepa]

--
 

 

Have a look to this great post about alpha and blending modes:

http://thread.gmane.org/gmane.comp.python.pyglet.user/3322/focus=3333

 

also, some editors dont output correct alpha RGBA images. Have you tried to open the images in other editors ?

--

claxo

[Peter Lu]

Hey, thanks for the speedy response.

It does seem to be an issue of editors. I took the images into gimp
and scaled them by 2x and then by .5x and that solved both issues
though I'm still not entirely sure what was going on before. I'll look
into that post you linked if I ever have issues like this again.

Thanks!

On Jan 18, 11:10 pm, claudio canepa <ccanep...@gmail.com> wrote:

[Jonathan Hartley]

Hey Peter. The thread claudio linked to is well worth scanning
through, then pause for detailed reading of the first post by Brian
Fisher. It illuminated the subject for me, so much so that I felt
compelled to paraphrase Brian's text on my own blog (http://
tartley.com/?p=945
) when I saw another example of the same effect, to try and cement the
idea in my head.