[gdal-dev] Best way to mosaic and compress lots of tiff Black/white?

[Pietro Rossin]

Ok
I made a test VRT and I applied your gdal_translate command.
It work and the result is a tiff with a weight of about the sum of the two
test mosaiced tiffs.
But as you can see in this image

http://www.flickr.com/photos/90029615@N05/8184720800/

the two tiffs have a white orizzontal stripe that separate them.
This is because each tif to be mosaiced have a white frame and every frame
overlap to "data" areas of adiacent images.

If I eliminate the 255 value from original tiffs the result is like this
http://www.flickr.com/photos/90029615@N05/8184744636/

I tried using -a_nodata 255 in gdal_translate command but the result is the
same white separation..

How can I set 255 values to nodata before mosaic each tiff?

Thank you very much for your help!
Pietro


2012/11/13 MORREALE Jean Roc [via OSGeo.org] <
ml-node+s1560n5016032h37 at n6.nabble.com>

> Hi,
>
> You could start by merging all your tiff in a VRT then do
> gdal_translate -of Gtiff -co SPARSE_OK=TRUE -a_nodata 0 -co NBITS=1 -co
> "TILED=YES" -co "COMPRESS=CCITTFAX4" -co "INTERLEAVE=BAND" "example.vrt"
> "example.tif"
>
> Le 2012-11-13 17:14, Pietro Rossin a écrit :
>
> > Hello all
> > I have ~1000 tiff/tfw RGB but with only 0 or 255 color value in all
> > bands
> > (black/white).
> > I want to mosaic them in a single image to be used in qgis and other
> > gis
> > software.
> >
> > Which is the best way to do this? And to compress the resulting
> > image? May
> > be Tiff?? Single band??
> > Another problem is that I must apply a formula to input images to
> > transform
> > 255 value to null, because of some white portion of each image that
> > overlap
> > to black portion of the adiacent one..
> >
> > Thanks
> > Pietro
>
> Le 2012-11-13 17:14, Pietro Rossin a écrit :
>
> > Hello all
> > I have ~1000 tiff/tfw RGB but with only 0 or 255 color value in all
> > bands
> > (black/white).
> > I want to mosaic them in a single image to be used in qgis and other
> > gis
> > software.
> >
> > Which is the best way to do this? And to compress the resulting
> > image? May
> > be Tiff?? Single band??
> > Another problem is that I must apply a formula to input images to
> > transform
> > 255 value to null, because of some white portion of each image that
> > overlap
> > to black portion of the adiacent one..
> >
> > Thanks
> > Pietro
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