RE: A CGM Question: handling transparency

[DULUC Franck <franck.duluc@airbus.com>]

Hi/bonjour, Lofton, Benoît,

 

    Thanks for having taken time to discuss it while I was sleeping :-).

 

    I have two questions:

        - Lofton, you give me the way to do it with WebCGM, what about ATA Profile ?

        - Benoît, the way you use defs/use SVG with rect and circle is a kind of workaround, but the question is how to have the canvas transparent. Then you said that canvas in SVG are initialized to transparent black. As I am a user and more a computer scientist than a graphical art specialist, what is transparent black? This is said many times in SVG but I did not manage to find a definition.

 

Regards and/et Cordialement,

 

Franck DULUC
AIRBUS FRANCE
SDND - Digital Data Definition and Research
B.P. D0611
316, route de Bayonne
31060 TOULOUSE Cedex FRANCE
Phone: (33)5.61.18.19.16
Fax: (33)5.61.93.59.44
mailto:franck.duluc@airbus.com

-----Message d'origine-----
De : Lofton Henderson [mailto:lofton@rockynet.com]
Envoyé : jeudi 28 août 2003 18:25
À : Benoit Bezaire
Cc : cgmopen members mailing list
Objet : RE: A CGM Question: handling transparency

Hi Benoit,
Hi Benoit,

At 12:16 PM 8/28/03 -0400, Benoit Bezaire wrote:

[...]

SVG 1.0 ... what is the background?  I.e., if you just have a simple file, <svg>...blah...blah...</svg>, what is the "...blah...blah..." drawn on or over?  You are much more involved with this than I, and I'm drawing a blank on the answer.  Is it well defined in the SVG 1.0 standard, or undefined (i.e., "nothing", transparent), or viewer-dependent?

[Benoit Bezaire] Yes, it is well defined.  A canvas in SVG 1.0/1.0 is always initialized to transparent black.  You can find more info at:

http://www.w3.org/TR/SVG11/render.html#Grouping

http://www.w3.org/TR/SVG11/render.html#Elements

 

Thanks, that's the bit that I couldn't remember.

The WebCGM solution that I proposed earlier achieves that same effect -- choose the RGB-alpha colour model, and set BACKGROUND COLOUR to (0,0,0,0).

Cheers,
-Lofton.