opacity & alpha

Alpha, used for opacity, is defined to be any real number.  The prose goes
on to say: If the value represented is less than 0.0, then it must be
interpreted as equal to 0.0; similarly, if the value represented is greater
than 1.0, then it must be interpreted as 1.0.

 

The schema datatypes module defines:

 

1.       "alpha" but constrains it to 0-1.  A good idea, but wrong.

2.       "opacity" as xs:string (doesn't use "alpha")

 

I can't think of why a dataype, "alpha", should be other than 0-1, and it is
not used for anything else in TTML.  So I propose:



1.       The prose be changed to constrain it to 0-1 and remove the text
quoted above about what to do if it isn't.

2.       Either way, the schema be changed to use the "alpha" datatype
(however we define it).

 

Regards,

 

                Mike

 

 

Michael A DOLAN

Television Broadcast Technology, Inc

PO Box 190, Del Mar, CA 92014 USA

+1-858-882-7497 (m)