Interfaces: PC and MAC and the screenGamma property...

[Alex Rice]

On Jan 2, 2004, at 10:21 PM, Scott Rossi wrote:

> The following article provides one explanation as to what is going with
> PNGs.  If the author's statements are valid, then apparently the 
> problem
> with PNG display is universal.
>
>   http://www.hut.fi/u/hsivonen/png-gamma.html
>
> Still, this shouldn't really pose any problem for Rev developers.

That hsivonen article is good, and makes me wonder some things about 
Rev:

1) What exactly does setting the screenGamma property do?  Does it 
cause a "correction"? Is Rev making the problem worse by even offering 
the screenGamma capability? That question occurs to me only because of 
this passage: from the hsivonen article:

	"Writing bogus gamma information to files and then doing gamma 
“correction” using different bogus gamma information is not solving the 
problem—only perturbing it further."

2) As a Rev developer, what's the best approach of those mentioned in 
the hsivonen article- "Opting out" or "Making the Color Spaces Match"?

I guess experimentation is the only way to arrive at a method that's 
good for you. Here is my demo stack
open stack URL "http://mindlube.com/download/files/runrev/gammatest.rev"

I created an image in Graphic Converer (Mac) and saved it as GIF, GMP, 
PNG with-Gamma-value and PNG-without-Gamma-value. The PNG without Gamma 
value is the "Opting out" method mentioned above.

The results are kind of unexpected, but seem to offer a good solution:

Rev on Mac AND Windows- if I set the screenGamma to 2.2, then the BMP, 
GIF and PNG-without-Gamma all are the same color! The 
PNG-with-Gamma-value is the oddball, and that was expected in the 
"Opting out" approach.

With screenGamma of 1.7, then strangely the GIF and the 
PNG-with-gamma-value are the same color, and the BMP and 
PNG-without-gamma-value are another color.

So save your PNGs without Gamma values, and set the screenGamma to 2.2, 
and you are good to go on Mac and Win.

This is interesting for me because I'm brainstorming up some games and 
will probably use
JPG, GIF and PNGs all mixed together.

Alex Rice <alex at mindlube.com> | Mindlube Software | 
<http://mindlube.com>

what a waste of thumbs that are opposable
to make machines that are disposable  -Ani DiFranco