color lib

[Manu via Digitalmars-d]

On 11 October 2016 at 18:10, Andrea Fontana via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On Monday, 10 October 2016 at 23:26:53 UTC, Manu wrote:
>>
>> I'm not sure why it matters what format the colour you have is...
>> Strings are in the form #RRGGBB, or #AARRGGBB. That is all.
>> It's the standard I've seen used everywhere ever, including the web,
>> which is a pretty good precedent :P
>
>
> If the web is a good precedent (CSS4 specs):
> "The first 6 digits are interpreted identically to the 6-digit notation. The
> last pair of digits, interpreted as a hexadecimal number, specifies the
> alpha channel of the color, where 00 represents a fully transparent color
> and ff represent a fully opaque color."
>
> https://drafts.csswg.org/css-color/#hex-notation
>
> CSS3 doesn't support hex string with alpha but they suggest you to use
> rgba() function. I think argb() doesn't exists instead.
> https://www.w3.org/TR/2011/REC-css3-color-20110607/#rgba-color
>
> Chrome 52 supports it:
> https://googlechrome.github.io/samples/css-alpha-channel/
>
> Android instead:
> https://developer.android.com/reference/android/graphics/Color.html#parseColor(java.lang.String)
> "Parse the color string, and return the corresponding color-int. If the
> string cannot be parsed, throws an IllegalArgumentException exception.
> Supported formats are: #RRGGBB #AARRGGBB [...]"
>
> Please notice that on PNG file format rgba is quite common (also on bmp with
> semi-official apha support)
> PNG: http://www.libpng.org/pub/png/book/chapter08.html

Oh dear... thanks for digging that up.
I didn't know the web had a standard for alpha. Certainly 0xAARRGGBB
has been used in windows code for as long as I've been programming...
but now there's a competing #RRGGBBAA version...
How to resolve this? I guess, go with the web? I should probably
change it to the CSS4 way.