Translating MrSid lossy compressed files into uncompressed imagery has its drawbacks, including licensing and artifacts.
Old versions of fwtools, which includes the GDAL utilities (and more), were compiled with a license that allowed for the translation of MrSid into e.g. Erdas Imagine images or GeoTiff. The licensing changed on that library, so FWTools and MS4W don’t do this anymore.
If you have a compiled version of the GDAL utilities with a legal license for converting, you still run into the issue of artifacts, e.g.
GDAL’s nearblack is a great utility for correcting this problem. If we wanted to batch this up on a windows system, it might look something like this:
FOR %f IN (*.sid) DO nearblack -o %~nf.img %f