今天研究了一下MrSID希望跟大家分享一下
Introduction to MrSID.
What is MrSID?
MrSID is an acronym for Multi-resolution Seamless Image Database, a powerful wavelet-based image compressor, viewer and file format for massive raster images that enables instantaneous viewing and manipulation of images locally and over networks while maintaining maximum image quality. Features include unprecedented compression ratios while maintaining highest image quality, true multiple resolutions, selective decompression, seamless mosaicking and browsing.
Does GIS software support MrSID?
Yes! Most importantly, as far as MassGIS is concerned, the MrSID Portable Image Format integrates seamlessly with today's most popular GIS software from ESRI, Intergraph, ERDAS, MapInfo, Bentley, Autodesk, and others. Lizardtech provides a web browser plug-in and a free Viewer. See http://www.lizardtech.com/download/dl_options.php?page=viewers for details.
How can I get more information on MrSID?
MrSID technology is patented and developed by LizardTech, Inc. of Seattle. For more information on MrSID visit the LizardTech web site at http://www.lizardtech.com/.
摘自：http://www.mass.gov/mgis/mrsid.htm
Geographic information systems
MrSID was developed primarily for Geographic Information Systems (GIS). With this format, large raster image files such as aerial photographs or satellite imagery are compressed and can be quickly viewed without having to uncompress the entire file.
World Wide Web
Since MrSID files contain multiple scale and quality levels they are claimed to be well suited for streaming over the World Wide Web. Only the requested zoom and area of the image is sent to the browser making the drawing/navigating/viewing performance extremely fast. The MrSID (.sid) format is supported in all major GIS applications such as ESRI, ERDAS, Autodesk, MapInfo, Intergraph and other product lines.
GeoExpress, the product that writes the MrSID format, can also generate JPEG 2000 (.jp2) data. When combined with LizardTech's Express Server, .sid and .jp2 data can be served quickly to a variety of GIS applications and other client applications either through direct integrations or via WMS (open source).
Software
LizardTech offers a software package called GeoExpress to read and write MrSID files. They also provide a free web browser plug-in. Most commercial GIS software packages can read MrSID files including those from GE Smallworld, ESRI, Intergraph, Bentley Systems, MapInfo, Safe Software, Autodesk, with ERDAS IMAGINE being able to both read and write MrSID files.
There is no Open Source implementation of the MrSID format. Some Open Source GIS systems can read MrSID files, including MapWindow GIS and those based on GDAL. The Decode Software Development Kit (SDK) is made available as a free download from developer.lizardtech.com. This enables the capability to implement MrSID reading capability in any application.
Some image editing and management software systems can also read MrSID files; Xnview, IrfanView
Technology
Encoding
MrSID technology uses lossless wavelet compression to create an initial image. Then the encoder divides the image into zoom levels, subbands, subblocks and bitplanes. After the initial encoding, the image creator can apply zero or more optimizations. While 2:1 compression ratios may be achieved losslessly, higher compression rates are lossy much like JPEG-compressed data.
Decoding
MrSID uses selective decoding meaning that the decoder does not have to decode the entire file to view a specific zoom level, image quality or scene for example.
转载自：http://en.wikipedia.org/wiki/MrSID
在ArcGIS Desktop中能够生成多大的MrSID影像？
问题：
ArcGIS Desktop核心和扩展功能能够生成多大的MrSID影像？
回答：
ArcView、ArcEditor或ArcInfo都能够将简单的栅格数据存成MrSID格式。小于50MB的任何单个栅格数据，都能够在ArcCatalog中进行转换。如果购买了额外的MrSID的许可，总量小于500MB的多个栅格数据能够被转到一个MrSID文件中。
上述的文件大小指的是未压缩的文件大小。如果输入的栅格数据是49MB或更小，但它已经被压缩了，未授权的核心编码器可能不能够压缩和转换它。如果原始影像已经是高度压缩了的，那么额外授权的许可编码器也可能无法压缩和转换它（取决于该影像未压缩时的数据量大小是否大于500MB）。下面举例说明如何判断输入影像的大小。当然，我们也可参考ArcToolbox中提供的栅格转MrSID工具的在线帮助。
我们可以通过栅格影响的宽度和高度（像素数）以及波段数来计算栅格数据集的大小。例如一个8位的RGB TIFF栅格数据将是1000×1000个像素也就是((1000 x 1000 x 3) / 1048576) = 2.86 MB大小。
