Re: [css3-color] #rrggbbaa annotation

On Apr 5, 2010, at 11:09 PM, Patrick Garies wrote:

> Alpha transparency in hexadecimal will likewise become incomprehensible for many authors and readers if added; the formula isn't even the same because you're doing a conversion to 100 instead of 255 so that's another calculation to remember:
> 
> To 255: 15a + b;
> Example: #BC
> 1. 15(11) + 12
> 2. 165 + 12
> 3. 177 Red/Green/Blue
> 
> To 100: (15a + b) / 255;
> Example: #BC
> 1. (15(11) + 12) / 255
> 2. (165 + 12) / 255
> 3. 177 / 255
> 4. 69.4% Opacity

This seems to assume that 0-255 is a natural way for an author to think about color channels, but not about alpha channels. All four channels are pretty much equivalent to me when I start thinking of a particular value in one. I figure the midway point is somewhere 127.5 on one scale, and between 7E and 7F on the other. I never do the math; I either use a color picker or I poke about with lighter or darker values in each channel. Thinking in terms of 0-255 is not much more natural to me than thinking in terms of 0-16.