# MrSID --- Multi-resolution Seamless Image Database

MrSID is a wavelet-based image compression technology which can utilise both lossy and lossless encoding. This technology was acquired in its original form from Los Alamos National Laboratories (LANL), where it was developed under the aegis of the U.S. government for storing fingerprints for the FBI. Now is is developed and distributed by the LizardTech, Inc.

This driver supports reading of MrSID image files using LizardTech's decoding software development kit (DSDK). This DSDK is not free software, you should contact LizardTech to obtain it (see link at end of this page). If you are using GCC, please, ensure that you have the same compiler as was used for DSDK compilation. It is C++ library, so you may get incompatibilities in C++ name mangling between different GCC versions (2.95.x and 3.x).

Latest versions of the DSDK also support decoding JPEG2000 file format, so this driver can be used for JPEG2000 too.

## Metadata

MrSID metadata transparently translated into GDAL metadata strings. Files in MrSID format contain a set of standard metadata tags such as: IMAGE__WIDTH (contains the width of the image), IMAGE__HEIGHT (contains the height of the image), IMAGE__XY_ORIGIN (contains the x and y coordinates of the origin), IMAGE__INPUT_NAME (contains the name or names of the files used to create the MrSID image) etc. GDAL's metadata keys cannot contain characters `:' and `=', but standard MrSID tags always contain double colons in tag names. These characters replaced in GDAL with `_' during translation. So if you are using other software to work with MrSID be ready that names of metadata keys will be shown differently in GDAL.

## Georeference

MrSID images may contain georeference and coordinate system information in form of GeoTIFF GeoKeys, translated in metadata records. All those GeoKeys properly extracted and used by the driver. Unfortunately, there is one caveat: old MrSID encoders has a bug which resulted in wrong GeoKeys, stored in MrSID files. This bug was fixed in MrSID software version 1.5, but if you have older encoders or files, created with older encoders, you cannot use georeference information from them.

## Creation Options

MrSID writing is only supported if GDAL is built against a MrSID ESDK 5.x or newer. This is normally only licensed by Lizardtech under controlled circumstances (whereas the DSDK is free for anyone to use within the constraints of a license agreement). If you do have the ESDK, it can be used to write MrSID files. The following creation options are supported.

- WORLDFILE: Yes to write an ESRI world file (with the extension .sdw).

- VERSION: Can be 2 for MrSID version 2 files, or 3 for MrSID version 3 files.

- COMPRESSION: Used only for version 2 MrSID files. Indicates the desired compression ratio. MrSID generation 2 cannot compress an image losslessly; so zero does not indicate numerically lossless compression. A value of one may be used for highest fidelity, but a value of twenty will generally yield the best results (a "visually lossless" compression). Twenty would indicate a 20:1 compression ratio (the image would be compressed to 1/20 its original size).

- FILESIZE: Used only for version 3 MrSID files. Indicates the desired output file size in bytes. Use "0" for lossless compression.

- TWOPASS: Used only with 3 MrSID files. Indicates that a two pass optimizer algorithm should be used during compression.

## See Also:

- Implemented as `gdal/frmts/mrsid/mrsiddataset.cpp`.

- LizardTech's Web site