Alpha revisit

The more I work with SDL the more I realize how limited the way SDL handles
alpha is. It would’ve been nice if I can explicitly specify alpha off, surf
alpha, or channel alpha. Couple with limited or differently behaving
hardware, this can get very frustrated and sometimes helpless at achieving a
certain effects.

Bottom line, was there some sort of technical reason, like too difficult to
implement, for this?

joel…

I think portability. Many platforms do not feature some of the alpha
capabilities you’re asking for to my knowledge. Would someone more
knowledgeable comment / correct me?On Tue, 2002-07-09 at 15:51, Joel Chen wrote:

The more I work with SDL the more I realize how limited the way SDL handles
alpha is. It would’ve been nice if I can explicitly specify alpha off, surf
alpha, or channel alpha. Couple with limited or differently behaving
hardware, this can get very frustrated and sometimes helpless at achieving a
certain effects.

Bottom line, was there some sort of technical reason, like too difficult to
implement, for this?

hmmm…, I guess it’s pushing it to ask about combining surf and pixel
alpha (ie. apply surf alpha, and then pixel alpha) then.

Basically I’ve got my hands tie here because I need to display a RGBA
surface at 50% and I am trying to see if there’s any hoops I can jump
through with what current SDL has to achieve it. I can’t transfer it to RGB
surf because I would lose the pixel alpha, which is important.

OpenGL is out of the question.

so far, the only way I’ve came up with is to lock the surface and
modify the alpha values myself and then reload my data after I am done.> -----Original Message-----

From: DrEvil [mailto:drevil at warpcore.org]
Sent: Tuesday, July 09, 2002 2:21 PM
To: sdl at libsdl.org
Subject: Re: [SDL] Alpha revisit

On Tue, 2002-07-09 at 15:51, Joel Chen wrote:

The more I work with SDL the more I realize how limited the
way SDL handles
alpha is. It would’ve been nice if I can explicitly
specify alpha off, surf
alpha, or channel alpha. Couple with limited or
differently behaving
hardware, this can get very frustrated and sometimes
helpless at achieving a
certain effects.

Bottom line, was there some sort of technical reason, like
too difficult to
implement, for this?

I think portability. Many platforms do not feature some of the alpha
capabilities you’re asking for to my knowledge. Would someone more
knowledgeable comment / correct me?

— Joel Chen wrote:

hmmm…, I guess it’s pushing it to ask about
combining surf and pixel
alpha (ie. apply surf alpha, and then pixel alpha)
then.

Basically I’ve got my hands tie here because I need
to display a RGBA
surface at 50% and I am trying to see if there’s any
hoops I can jump
through with what current SDL has to achieve it. I
can’t transfer it to RGB
surf because I would lose the pixel alpha, which is
important.

OpenGL is out of the question.

so far, the only way I’ve came up with is to
lock the surface and
modify the alpha values myself and then reload my
data after I am done.

I’m working on this, but I’m sure it won’t be in CVS
at least until 1.3…

-Loren__________________________________________________
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That’s great! As long as SDL defines an interface for better alpha
handling, that’s good enough for me.> -----Original Message-----

From: Loren Osborn [mailto:linux_dr at yahoo.com]
Sent: Tuesday, July 09, 2002 4:03 PM
To: sdl at libsdl.org
Subject: RE: [SDL] Alpha revisit

— Joel Chen <@Joel_Chen> wrote:

hmmm…, I guess it’s pushing it to ask about
combining surf and pixel
alpha (ie. apply surf alpha, and then pixel alpha)
then.

Basically I’ve got my hands tie here because I need
to display a RGBA
surface at 50% and I am trying to see if there’s any
hoops I can jump
through with what current SDL has to achieve it. I
can’t transfer it to RGB
surf because I would lose the pixel alpha, which is
important.

OpenGL is out of the question.

so far, the only way I’ve came up with is to
lock the surface and
modify the alpha values myself and then reload my
data after I am done.

I’m working on this, but I’m sure it won’t be in CVS
at least until 1.3…

-Loren


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