[mapserver-dev] Handling alpha values in colors

[thomas bonfort]

Tamas,
The handling of alphas in colors is a bit flakey, I agree. The initial
aim when we worked on this at the montreal code sprint was to drop
support of the OPACITY keyword at the STYLE level in the mapserver
library (while maintaining it in the parser for backwards
compatibility), by allowing colors to be specified with quadruplets
instead of triplets. I don't rememember the reason (Steve might
recollect), but in the end having the parser be able to parse both
triplet and quadruplet integers was not possible, and we are thus
stuck in this less than ideal state.
If someone has a solution for this parser problem that would be great,
as it would open up varying opacity for all *COLOR entries.

regards,
thomas

On Sun, Sep 23, 2012 at 11:38 AM, Tamas Szekeres <szekerest at gmail.com> wrote:
> Hi All,
>
> I don't properly understand how we intend to handle alpha values of colors
> in mapserver. Currently the alpha values can be specified in mapfiles (by
> using the hexadecimal format), but that values are not written back to the
> file in msSaveMap.
> Style level opacity seems to override alpha values specified in mapfiles,
> but on the other hand we cannot specify opacity at some places (like in
> label text colors).
> By using the opacity values of styles seems to change the alpha values of
> multiple properties (color, outlinecolor, background color etc.) which
> doesn't seems to be as such generic as specifying the alpha values for the
> colors individually.
>
> I can also see the conditional compilation flag ALPHACOLOR_ENABLED in the
> code, but it doesn't have much effect for the operation.
>
> Could someone explain how the things are expected to work?
>
> Best regards,
>
> Tamas
>
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