“This way 0 represents “full transparency” and that just doesn’t computer in
my head.”
The should say “doesn’t compute in my head” of course. Pardon me for
correcting such a pathetic little thing, but it was embarrassing 
Regards
Rickard Andersson
How about “0 alpha results in no effect on target pixels”?
Or just think of alpha as opacity instead of transparency.
//David Olofson — Programmer, Reologica Instruments AB
.- M A I A -------------------------------------------------.
| Multimedia Application Integration Architecture |
| A Free/Open Source Plugin API for Professional Multimedia |
----------------------------> http://www.linuxdj.com/maia -' .- David Olofson -------------------------------------------. | Audio Hacker - Open Source Advocate - Singer - Songwriter |-------------------------------------> http://olofson.net -'On Thursday 22 November 2001 00:19, Rickard Andersson wrote:
“This way 0 represents “full transparency” and that just doesn’t
computer in my head.”
How about “0 alpha results in no effect on target pixels”?
Or just think of alpha as opacity instead of transparency.
Yeah, but is it just me or does that sound more “backwards”?
What is “common practice” in the computer graphics realm?
Regards
Rickard Andersson
How about “0 alpha results in no effect on target pixels”?
Or just think of alpha as opacity instead of transparency.Yeah, but is it just me or does that sound more “backwards”?
Why? I find it rather logical to think of the source (“this”) data being
multiplied by the alpha, while the target (“that”) gets multiplied by
(“100%” - alpha). Note that it’s the source that brings the alpha
channel or level with it, not the target.
What is “common practice” in the computer graphics realm?
Well, GIMP, Photoshop and most other applications seem to use the opacity
style (0% = transparent, 100% = opaque), so in that respect, the new
semantics is compatible with how most graphics artists think about it.
When it comes to file formats, opacity and transparency seems to be more
evenly distributed, but I have actually never seen an application that
normally interprets alpha as “transparency” in the UI.
//David Olofson — Programmer, Reologica Instruments AB
.- M A I A -------------------------------------------------.
| Multimedia Application Integration Architecture |
| A Free/Open Source Plugin API for Professional Multimedia |
----------------------------> http://www.linuxdj.com/maia -' .- David Olofson -------------------------------------------. | Audio Hacker - Open Source Advocate - Singer - Songwriter |-------------------------------------> http://olofson.net -'On Thursday 22 November 2001 01:21, Rickard Andersson wrote:
How about “0 alpha results in no effect on target pixels”?
Or just think of alpha as opacity instead of transparency.Yeah, but is it just me or does that sound more “backwards”?
What is “common practice” in the computer graphics realm?
Alpha representing opacity rather than transparency is how OpenGL does it.
Since SDL added OpenGL support, it’d be better to keep them consistent to
keep the programmer from getting confused. But then again, OpenGL also
sets bottom-left corner of the screen as (0,0), not top-left… These
darn 3D libraries do it all backwards… 
All 2D libraries I’ve
seen sets alpha as transparency level (0 is fully opaque) and sets
top-left as (0,0); all 3D libraries I’ve seen sets alpha as opacity level
(0 is fully transparent) and sets bottom-left as (0,0).
-Mark
(got yelled at in graphics class for insisting 0 should be fully opaque)On Thu, 22 Nov 2001, Rickard Andersson wrote:
–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.