Re[2]: [cgmo-webcgm] RE intensity

[Benoit Bezaire <benoit@itedo.com>]

Tuesday, July 13, 2004, 8:16:20 PM, Lofton wrote:

LH> At 03:02 PM 7/13/2004 -0400, Benoit Bezaire wrote:
>>Hi all,
>>
>>I think we should go with this approach.  The main reason is that it
>>is simpler.  The HLS approach does work in an absolute scale, but not
>>very well on a relative scale.  I also recall people saying we wanted
>>to 'fade' the colors.  We should just add wording to say that the new
>>color values are clamped to [0..255].

LH> If we go with Forrest's equations (below), the clamping caveat is not a
LH> necessary part of the definition.  With the intensity parameter in the
LH> range [0,1], each component will be in the range [old_color,0xffff].  The
LH> only way that a component could go out of range (i.e., out of [0,0xffff])
LH> is if the parameter is out of range.

LH> That said, whether or not to say anything about clamping depends on what's
LH> the error philosophy -- the equations can only yield out-of-range results
LH> for illegal parameter values.

Who said intensity had to be limited to [0,1]? :-)  If it is a relative
intensity shouldn't I be allowed to go above 100% of the original
color?  I know it doesn't apply well to color that don't have a hue
ex: (255,0,0)... you end up in negative values as soon as you exceed
1 (or 100%).  But for a sky blue color (64,128,192) applying an
intensity of 1.25 (or 125%) would make it a darker blue.

Is there any use for that?  I guess I'm wondering if we should assume
we want to shade to white, what if the illustration background is
black?  This is way I introduced clamping into the discussion.

It's just an idea...

-- 
 Benoit   mailto:benoit@itedo.com