[gdal-dev] warp, translate and world files

[Paul Meems]

Hi list,

I've got several png files with worldfiles.
I need them in another projection (28992 --> 3785).
I'm using gdalwarp to reproject to a tiff file and then I use gdal_translate
to create a png file again.
My original png file is about 25 kB, the warped tiff is over 2MB and the
translated png file is over 80 kB.

The 80 kB file is workable. But I think I can get the same result using the
original png file but with a modified world file.
I did some tests and ended up with a world file that makes the png file load
in the correct location and with the correct width and height.
All I'm missing are the rotation values in the world file. I can see the
file needs to be rotated a bit, but can't figure out the algorithm behind
it.

Most likely I'm not the first person to do this so I'm asking if someone can
point me to the right direction.
Of course I did Google already.

Thanks,

Paul
The Netherlands (EPSG:28992)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/gdal-dev/attachments/20101025/05e7cf9f/attachment.html