Pima County Geographic Information Systems

Developing GIS data for the Web

Viewing MrSID Images

Overview

MrSID (Multi-resolution Seamless Image Database) is a highly compressed format used to store images of photographs.

You need either a web browser plugin or a standalone viewer program to view files in MrSID format:

• You can view MrSID files directly on the web by using the free ExpressView Browser Plugin (formerly MrSID Browser Plugin) you can download from LizardTech. The plug-in lets you view, pan, zoom, save and print the photos in MrSID format. Most users will use this ExpressView Browser Plugin, although it does not support measurement.

• You can also download a trial version of the $299 standalone program GeoExpress (formerly MrSID GeoViewer and GeoExpress View) from LizardTech. The standalone GeoExpress has added features including the ability to measure distance, measure area, and save a portion of the image. You can also turn on a grid by selecting View, Grid. Selecting Options, Georeference enables you to assign the distance each pixel represents to do measurements in real-world units.

• The free standalone MrSID GeoViewer has many features, such as measurement, that are now part of the pay-for GeoExpress program. Unfortunately, the MrSID GeoViewer is no longer available from LizardTech. If you already have the MrSID GeoViewer, you can continue to use it to view MrSID images on this website.

You can use GeoExpress (or the older MrSID GeoViewer if you have it) by accessing the MrSID image as a file in your file system. If you are using a web browser and have the ExpressView Browser Plugin (MrSID plugin) installed, then the browser plug-in will be used rather than the standalone viewer. If you want to use a standalone viewer such as GeoExpress with a file from the web, there are three situations:

• If you are viewing the image with the ExpressView Browser Plugin (MrSID plugin), you can right-click in the image and select "Save image as..." to save a local copy of the MrSID (.sid) file for viewing with the standalone MrSID Viewer. Or if you have a link to the image you can right-click on the link and use "Save Target As..." in Internet Explorer or "Save Link As..." in Netscape.

• If you have never installed the ExpressView Browser Plugin (MrSID plugin), then you can have your web browser open the standalone viewer as a "helper application." To do this, the .sid file extension needs to be associated with the standalone viewer. To set or check this setting, open My Computer, then Tools, then Folder Options... Select the File Types tab and scroll to the SID file type. Under "Details for 'SID' Extension" below it should have the name of the standalone viewer, either MrSIDGeoViewer or MrSIDViewer. If some other program is associated, choose "Change" and choose the MrSID viewer you want to use. Click OK to exit the dialogs.

• If you have installed the ExpressView Browser Plugin (MrSID plugin) and want to open a standalone viewer directly, then you need to uninstall the ExpressView Browser Plugin (MrSID plugin). (You also need to have the .sid file extension assocated with the standalone viewer as described above.) You can remove the plug-in with Control Panel, Add-Remove Sofware. Unfortunately, this leaves setting in the registry, the web browser still tries to use the plug-in and all you see is a red X on the screen. The solution is to edit the offending settings out of the registry. We hope to add more details on doing this at a later time ... (Apparently keys related to mrsid and mime types.) Editing the registry can harm your system. Be careful if you attempt this yourself.

Serving MrSID images

To serve MrSID (.sid) files and have them recognized by the ExpressView Browser Plugin (MrSID plugin), it is necessary to set the the MIME content type on the server for MrSID format. At least two MIME type definitions are in use.

• image/x-mrsid-image
• application/x-mrsid (This seems to be less common.)