# Re: [css3-color] #rrggbbaa annotation

From: Alex Meiburg <timeroot.alex@gmail.com>
Date: Sat, 15 May 2010 08:31:33 -0700
Message-ID: <AANLkTimjlqjK_rcBwehqeyZfU3eJyo7Fz9ijbtHPlnvj@mail.gmail.com>
To: Alan Gresley <alan@css-class.com>, www-style@w3.org
```1. The "0x" prefix before a number indicates that it will be in hex. There
are similar things, I believe, with the letter o for Oct, d for decimal,
etc.

2. Float just means any decimal number. That's opposed to an integer, which
is how the R, G, and B values are usually represented. Usually in computer
programming these numbers are called floats instead of fractions or
decimals.

~6 out of 5 statisticians say that the number of statistics that either make
no sense or use ridiculous timescales at all has dropped over 164% in the
last 5.62474396842 years.

On Fri, May 14, 2010 at 11:20 PM, Alan Gresley <alan@css-class.com> wrote:

> Boris Zbarsky wrote:
>
>> On 5/15/10 12:37 AM, Alan Gresley wrote:
>>
>>> 0x00 maps to 0
>>> 0x80 maps to 0.5
>>> 0xFF maps to 1.0
>>>
>>
>> I would think that Tab's issue was that while 1.0 - 0.5 == 0.5 - 0, 0xFF -
>> 0x80 != 0x80 - 0x00.
>>
>> So the real question is why 0x80 wouldn't map to 0.50196078431372548 if
>> we're going from hex to float.
>>
>
>
> 0x80 would map to 0.50196078431372548. You can not have a true halfway
> value. You have two sets of hexadecimals.
>
> 0#,1#,2#,3#,4#,5#,6#,7# (127 steps and 128 values)
>
>    _0.5 between two hexadecimals sets_
>
> 8#,9#,A#,B#,C#,D#,E#,F# (128 steps and 128 values)
>
> This is since each color channel (rgb) has 255 steps but 256 values. You
> can not divide 255 evenly so 0x80 is the closes to 0.5.
>
> Two questions:
>
>
> 1. What does the '0x' represent in 0x00?
>
> 2. What does float represent in where you write, "going from hex to float"?
>
>
>
>  Or put another way, if we have a set of 256 (really, any even number will
>> do) discrete values, there is no way to place them on the closed unit
>> interval in such a way that the spacing between two adjacent values is a
>> constant and one of the values lands on 0.5.
>>
>> -Boris
>>
>
>
> Correct, please see above :-)
>
>
>
> --
> Alan http://css-class.com/
>
> Armies Cannot Stop An Idea Whose Time Has Come. - Victor Hugo
>
>
```
Received on Saturday, 15 May 2010 16:01:06 UTC

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