Re: [cgmo-webcgm] RE intensity

[Benoit Bezaire <benoit@itedo.com>]

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].

-- 
 Benoit   mailto:benoit@itedo.com


Tuesday, July 13, 2004, 1:34:49 PM, Forrest wrote:

FC> All,

FC> My understanding was that we wanted to make some APS fade in color
FC> (go toward white) so other objects would stand out more in the image.
FC> So an intensity of 1 would not change the color and an intensity of 0 would
FC> make it white. Internally  in our applications we convert all colors to a range
FC> from 0 to 0xffff where (0xffff,0xffff,0xffff) is white. If we are going the
FC> other way
FC> how do you make red more intense, make it black?

FC> Forrest



FC> Forrest proposed a different system:

>>         new_color.red    = 0xffff - intensity*(0xffff - old_color.red);
>>         new_color.green = 0xffff - intensity*(0xffff - old_color.green);
>>         new_color.blue   = 0xffff - intensity*(0xffff - old_color.blue);

FC> I need clarification -- is this about subtractive color (ink) or additive
FC> (luminous)?  Because I was at first reading (0xffff,0xffff,0xffff) as
FC> white, in which case minimum intensity (=0) would lead to white and maximum
FC> intensity (=1) leads to "old_color" -- counter-intuitive.  On the other
FC> hand, if 0xffff is black, it makes more sense.  0 intensity is black, and 1
FC> intensity is "old_color".  I.e. with this system, what you do is traverse
FC> the difference from old_color to 0xffff (black or white).  (If subtractive)
FC> you can get dimmer than old_color but never brighter.

FC> -Lofton.