[maemo-developers] hildon_color_button & custom colors issue

[From: Aniello Del Sorbo]

On Wed, Apr 16, 2008 at 12:40 PM, Aniello Del Sorbo <anidel at gmail.com>
wrote:

>
> Anyway.. the first issue below happened because I was running Xournal from
> root in an SSH remote shell.
> Thus, probably, colormaps  were wrong.
> Running it the usual way (from the Menu) fixed a bit things.
> The GdkColor returned by the hildon color chooser was, when drawn on the
> canvas, slightly different from the one showed in the button itself.
> I think it looked darker.
>
> After digging a bit I figured out that the GdkColor RGB values where RGB16
> (guint16) while I needed the RGB8 format (for the "fill-color-rgba"
> property).
> Thus, I had to first divide red, green and blue by 255 before putting them
> into a single guint value (RGBA) in the form of 0xRRGGBBAA.
>
> guint rgba = GNOME_CANVAS_COLOR_A  (color->red / 255.0, color->green /
> 255.0, color->blue / 255.0, alpha)
>

Further corrected, the divisor should not be 255 but 257 (0x101) instead.
Otherwise the reduction from RGB16 to RGB8 does not work.
RGB16 is in the form: 0xRRRRGGGGBBBB i.e. values range from 0 to 65535
RGB8 is in the form 0xRRGGBB i.e. values range from 0 to 255.

Sorry if this is stuff people already know, but I am new to it and couldn't
find much about it.

-- 
anidel
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