[FWTools] gdaladdo & mapserver OFFSITE

Emmanuel BELO emmanuel.belo at camptocamp.com
Tue Mar 20 10:32:25 EST 2007

Dear List,

by preprocessing black and white tif images (in grayscale mode) with
gdaladdo we produce optimized images to use with mapserver.

In our mapfile, we set white to transparent with OFFSITE command.

When viewing the data at the original scale with an orthophoto behind,
it looks perfect, but when zooming out, a small white strip appears
between the black lines and the transparent area.

Is it due to the use of gdaladdo or is it due to Mapserver resampling

What are the best practices for processing this kind of data?

best regards,

Emmanuel BELO

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