[FWTools] gdaladdo & mapserver OFFSITE

[Emmanuel BELO]

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
process?

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

best regards,

Emmanuel BELO