[Mapserver-dev] Fix for broken pixmap transparency in 4.2 and 4.3 -> 4.2.4 release?

[Frank Warmerdam]

Sean Gillies wrote:
> Hi all,
> 
> I've come up with a fix for the long standing bug regarding
> the rendering of pixmaps with transparency onto RGB map images.
> 
>   http://mapserver.gis.umn.edu/bugs/show_bug.cgi?id=926
> 
> Commit is pending review by authors of mapdraw.c and mapgd.c.

Sean,

I looked int he bug report but only see a general description of the
solution, not the patches themselves.  Am I missing something?  I didn't
find the description quite clear.

> This would make 6 significant bug fixes since 4.2.3, and I'd
> like to request a 4.2.4 release before we get completely
> occupied with the work of releasing 4.4.0.  Yes?
 >
> While looking into the map rendering code, it appears to me that
> a nice feature for a future 5.0 release would be 7 bit alpha
> support for vector layers.  Say, if a style's color was defined
> like:
> 
>     COLOR 255 0 0 64
> 
> then the vectors would be rendered with ~50% transparency.

I believe that we should treat any alpha transparency values as 8bit
and just downgrade to 7 bit internally when applying to GD.  It would be
confusing to the user to user, and to developers of other rendering
modules to use 7bit alphas just because that is a limitation of GD.

Note that your change is basically to use RGBA for colorObj everywhere, right?
I do think that is very desirable though it may be a fair amount of work to
apply across the board.  No harm in rolling it out in sections though.

So, is the next version after 4.4 really 5.0 instead of 4.6?

Best regards,

---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent