Re: Transparency attribute in Bitmap class

Markku Savela (msa@anise.tte.vtt.fi)
Tue, 3 Feb 1998 13:25:21 +0200 (EET)

> From: Emmanuel BEUQUE <ebeuque@pratique.fr>
> I have found incredible that the dropOutColour attribute that was in DIS
> has simply disappeared in IS. This feature is so widely used in the TV
> world that this big loss always make authors angry.

I can see some rationale for the disappearance of dropOutColor. It
would work only for non-lossy image formats (such as GIF and PNG,
which already have their own internal transparency).

For JPEG and MPEG the exact color is problematic, because the decoded
color value is only an approximation of the encoded color
value. Putting a uniformly colored area into JPEG/MPEG, does not come
out as single color value, the resulting transparency would be a
random pixel here and there...

-- 
Markku Savela (msa@hemuli.tte.vtt.fi), Technical Research Centre of Finland
Multimedia Systems, P.O.Box 1203,FIN-02044 VTT,http://www.vtt.fi/tte/staff/msa/