Fw: [Mapserver-users] transparent background raster (tif)

[Rosangela Silva]

Hi
This message is a little late at list
and discard it please.
Thanks
Rosângela
----- Original Message ----- 
From: "Rosangela Silva" <rosangela.silva at zenitpolar.com.br>
To: "Frank Warmerdam" <warmerdam at pobox.com>
Cc: "Mapserver-Users at Lists. Gis. Umn. Edu"
<mapserver-users at lists.gis.umn.edu>
Sent: Tuesday, May 27, 2003 4:10 PM
Subject: Re: Fw: [Mapserver-users] transparent background raster (tif)


> Hi,
> My images are 8-bit TIFF, and they are peaces of sattelite
> images (Landsat - RGB composit).
> Part of these images has valid information,
> but another part is complemented with deep black color.
> I think that I couldn't specify a black collor pixel (0)
> like "transparent" because some lakes and rivers are black too.
> I'd like to show only the valid information.
> I'll try to send a tiff like an example.
> Thanks
> Rosângela
> ----- Original Message ----- 
> From: "Frank Warmerdam" <warmerdam at pobox.com>
> To: "Rosangela Silva" <rosangela.silva at zenitpolar.com.br>
> Cc: "Mapserver-Users at Lists. Gis. Umn. Edu"
> <mapserver-users at lists.gis.umn.edu>
> Sent: Tuesday, May 27, 2003 3:27 PM
> Subject: Re: Fw: [Mapserver-users] transparent background raster (tif)
>
>
> > Rosangela Silva wrote:
> > >  Hello,
> > >
> > >  I'm using mapserver 3.6.5.
> > >  I don't know how the mapserver interprets the background of the
> > >  tiff or jpg images. I'm looking for information about it, and some
> > >  softwares assumes the transparent background like a cannel "alpha",
> > >  but I don't know exactly how it works.
> > >  Sorry, but, for while, it is everything I know to explain.
> >
> > Rosângela,
> >
> > How it is accomplished will, as Ed suggests, depend on the nature of the
> > image.  MapServer 3.6.5 (if using GDAL for raster IO) will support
> treating
> > pixels with "alpha=0" as transparent if the image is RGBA.  If the image
> is
> > in a format that returns a "nodata" value, or knows that particular
color
> > indexes in a paletted image are transparent, they will be automatically
> > treated as transparent.  3.6.x does *not* support the user indicating a
> > particular RGB value as transparent for 24bit inputs, but the OFFSITE
> value
> > can be used to mark one raw pixel value for greyscale or paletted images
> > that should be treated as transparent.
> >
> > I hope this helps.
> >
> > 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
> >
> >
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> > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
> >
>