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Posted by Onideus Mad Hatter on 01/16/07 23:11
On 13 Jan 2007 03:48:29 GMT, jasen <jasen@free.net.nz> wrote:
>On 2007-01-12, Onideus Mad Hatter <usenet@backwater-productions.net> wrote:
>> On 12 Jan 2007 02:26:05 -0800, sl@f0r7r355.org wrote:
>
>> ...wow...even Wikipedia FAILS to explain it with anything other than
>> the most simplistic glazing jive of redundant incoherency. Tsch,
>> tsch, tsch...a simple formula/equation is just TOO MUCH to ask
>> apparently. Oh how the mighty web has fallen.
>>
>
>Binary RGB:
>
> RGB colours are represented in the low 24 bits of a 32-bit number
>
> 8bits for red
> 8bits for green
> 8bits for blue
>
> to convert 8-bit unsigned (0..255) R,G, and B values to an RGB value
> you need to shift the red 16 bits and the green 8 bits to the left
>
> this means multiplying red by 65536 and green by 256 and then adding
> them all up.
>
>one easy way to do this is to write them in hex.
So let's use the base numbers:
13
162
189
The formula you just gave: (r * 65536)+(g * 256)
The formula you gave before:
var rgb : String = "0x" + ((r*256+g)*256+b).toString(16);
In the first we get:
(13 * 65536)+(162 * 256) = 893440
In the second we get:
(13*256+162)*256+189 = 893629
Convert the two to hex:
0DA200
0DA2BD
And then convert the two digit hex codes back to decimal:
13,162,0
13,162,189
Ahhh, I see where you failed, you forgot to mention that you needed to
ADD the blue. So the formula should ACTUALLY be:
(r * 65536)+(g * 256)+b
or you can alternatively write it as:
(r*256+g)*256+b
So that's good, we have a formula now...we're still missing the
EXPLANATION however. You said:
> to convert 8-bit unsigned (0..255) R,G, and B values to an RGB value
> you need to shift the red 16 bits and the green 8 bits to the left
....but what you don't say is WHY. What ~exactly~ is the correlation
between the two? I mean I understand RGB, each represents a base
additive color with a range between 0 and 255. But what EXACTLY are
these multiplied values in relation to their original RGB values? Is
it just mathematical parlor tricks to shorten the amount of bits that
represent each color or is there some ACTUAL meaning behind the
numbers?
--
Onideus Mad Hatter
mhm ¹ x ¹
http://www.backwater-productions.net
http://www.backwater-productions.net/hatter-blog
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