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<html><head> <title>MrSID --- Multi-resolution Seamless Image Database</title></head><body bgcolor="#ffffff"><h1>MrSID --- Multi-resolution Seamless Image Database</h1>MrSID is a wavelet-based image compression technology which can utilise bothlossy and lossless encoding. This technology was acquired in its originalform from Los Alamos National Laboratories (LANL), where it was developedunder the aegis of the U.S. government for storing fingerprints for the FBI.Now is is developed and distributed by the LizardTech, Inc.<p>This driver supports reading of MrSID image files using LizardTech's decodingsoftware development kit (DSDK). <b>This DSDK is not free software, you shouldcontact LizardTech to obtain it (see link at end of this page).</b> If you areusing GCC, please, ensure that you have the same compiler as was usedfor DSDK compilation. It is C++ library, so you may get incompatibilitiesin C++ name mangling between different GCC versions (2.95.x and 3.x).<p>Latest versions of the DSDK also support decoding JPEG2000 file format, so this driver can be used for JPEG2000 too.<p><h2>Metadata</h2>MrSID metadata transparently translated into GDAL metadata strings. Filesin MrSID format contain a set of standard metadata tags such as:IMAGE__WIDTH (contains the width of the image), IMAGE__HEIGHT (contains theheight of the image), IMAGE__XY_ORIGIN (contains the x and y coordinatesof the origin), IMAGE__INPUT_NAME (contains the name or names of the filesused to create the MrSID image) etc. GDAL's metadata keys cannot containcharacters `:' and `=', but standard MrSID tags always contain double colonsin tag names. These characters replaced in GDAL with `_' during translation.So if you are using other software to work with MrSID be ready that namesof metadata keys will be shown differently in GDAL.<p><h2>Georeference</h2>MrSID images may contain georeference and coordinate system information inform of GeoTIFF GeoKeys, translated in metadata records. All those GeoKeysproperly extracted and used by the driver. Unfortunately, there is onecaveat: old MrSID encoders has a bug which resulted in wrong GeoKeys, storedin MrSID files. This bug was fixed in MrSID software version 1.5, but if youhave older encoders or files, created with older encoders, you cannot usegeoreference information from them.<p><h2>Creation Options</h2>MrSID writing is only supported if GDAL is built against a MrSID ESDK5.x or newer. This is normally only licensed by Lizardtech under controlledcircumstances (whereas the DSDK is free for anyone to use within the constraints of a license agreement). If you do have the ESDK, it canbe used to write MrSID files. The following creation options are supported.<ul><li> WORLDFILE: Yes to write an ESRI world file (with the extension .sdw). <p><li> VERSION: Can be 2 for MrSID version 2 files, or 3 for MrSID version 3files.<p><li> COMPRESSION: Used only for version 2 MrSID files. Indicates the desiredcompression ratio. MrSID generation 2 cannot compress an image losslessly; sozero does <i>not</i> indicate numerically lossless compression. A value ofone may be used for highest fidelity, but a value of twenty will generallyyield the best results (a "visually lossless" compression). Twenty wouldindicate a 20:1 compression ratio (the image would be compressed to 1/20 itsoriginal size).<p><li> FILESIZE: Used only for version 3 MrSID files. Indicates the desiredoutput file size in bytes. Use "0" for lossless compression.<p><li> TWOPASS: Used only with 3 MrSID files. Indicates that a two pass optimizer algorithm should be used during compression.<p></ul><h2>See Also:</h2><ul><li> Implemented as <tt>gdal/frmts/mrsid/mrsiddataset.cpp</tt>.<p><li> <a href="http://www.lizardtech.com">LizardTech's Web site<a><p></ul></body></html>⌨️ 快捷键说明
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