[Qgis-user] Transparency settings in qml file ignored by rasters

[Alister Hood]

Hi,
You might be able to work around the problem by loading all of the 
images into QGIS, setting the transparency for one image and saving 
the project file, then opening it in a text editor (or whatever) and 
using find and replace.

Regards,
Alister


> Date: Tue, 10 May 2011 08:24:14 +0200
> From: Agustin Lobo <alobolistas at gmail.com>
> Subject: Re: [Qgis-user] Transparency settings in qml file ignored by
> 	rasters?
> To: giovanni.manghi at gmail.com
> Cc: qgis-user <qgis-user at lists.osgeo.org>,	qgis-developer
> 	<qgis-developer at lists.osgeo.org>
> Message-ID: <BANLkTikwWGO+=aq5sZ80Qi0Ktr2K_4Ovuw at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Thanks for the suggestion, but I must avoid writing warped images at
> this stage. The georeferencing is only approximate
> as it is based on the crude navigation system of the miniUAV. The tfw
> file is intended to have a first
> positioning of the image on the map to check results and, eventually,
> to facilitate locating ground control points.
> A more accurate geometric processing, producing a mosaic, is done at a
> later stage.
> Displaying these rotated images is slow also. But the big problem is
> not being able to select the triple 0
> as transparent by default.
> I've put an example of the display here:
> https://sites.google.com/site/filestemp2/home/transp.jpeg
> where some images have the triple 0 as transparent while others do not
> and show the inconvenient black background.
> 
> Agus
> 
> 2011/5/9 Giovanni Manghi <giovanni.manghi at gmail.com>:
> > Hi,
> >
> >> I have hundreds of images from a miniUAV, and all of them
> >> are rotated according to a tfw file. QGIS positions the image
within
> >> a rectangle of 0, so I need to set 0,0,0 to transparent, otherwise
> >> most of the area is overlapped by black.
> >> Doing this manually for each image is tedious...
> >
> >
> > meanwhile you can use gdaltools in batch mode and with warp or
translate
> > set "-dstnodata 0" or "-a_nodata 0".
> >
> > By the way, do you have any performance issue with rotated images?
> >
> > see https://trac.osgeo.org/qgis/ticket/3794
> >
> >
> > cheers
> >
> > -- Giovanni --