[Qgis-developer] Re: [Qgis-user] Transparency settings in qml file ignored by rasters?

[Agustin Lobo]

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 --
>
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