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Producing potable color images from IDL? [message #32972]

Sun, 24 November 2002 07:04

Chris Mulliss
Messages: 5
Registered: March 2000

Junior Member

Hello,

This is not strictly an IDL question, but here goes...

When I produce 24-bit color images in IDL (running on a SUN) and try to
display them on an SGI or Windows box, they tend to come out looking very
dark.

I have been told that it is probably a hardware-dependent gamma correction
problem. I have been told also that the PNG image format has the ability to
store the gamma value of the machine that the image was created so that the
image can be "gamma corrected" on other platforms. IDL's help on PNG does
not mention this feature and I have this problem with all file formats that
I have tried including PNG.

So, does anybody know what is going on? Has anyone found a way to make
images in IDL that don't look dark on other platforms? Does anyone have a
reference to the mathematical nature of this "gamma correction" so that I
look into accounting for it in code.

Thanks,
Chris

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Re: Producing potable color images from IDL? [message #33057 is a reply to message #32972]

Mon, 25 November 2002 10:00

Rick Towler
Messages: 821
Registered: August 1998

Senior Member

"Chris Mulliss" <cmulliss@columbus.rr.com> wrote

> I have been told that it is probably a hardware-dependent gamma correction
> problem. I have been told also that the PNG image format has the ability
to
> store the gamma value of the machine that the image was created so that
the
> image can be "gamma corrected" on other platforms.

This is true:

http://www.libpng.org/pub/png/spec/PNG-DataRep.html#DR.Gamma -correction

This might help too:

http://www.libpng.org/pub/png/spec/PNG-GammaAppendix.html

> IDL's help on PNG does not mention this feature and I have
> this problem with all file formats that I have tried including PNG.

As David mentioned, IDL doesn't support this feature. libPNG does support
this feature (I think) so you could write your own png import/export
routines that incorporate gamma correction into the image. The only problem
would be getting a "system" gamma from the machine when you create the
image.

Your best bet is to calibrate the systems that you will be viewing your
images on. Most better monitors in the PC and Mac realm come with color
correction utilities. It might be more difficult to find such software on
the Sun/SGI side. Alternatively you could come up with your own calibration
system and use a viewer you write in IDL to apply corrections on each
machine. Or, just turn the brightness down on your Sun monitor :)

-Rick

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