Transparency with MrSID background data

For many years ERDAS IMAGINE has not provided correct transparency creation with the IMAGINE MrSID Encoders. This was addressed in 9.3 and continues on through the 9.3 Service Packs and into ERDAS IMAGINE 2010. Yet, it is not obvious how to do this.

The user must set the NoData (NullData) in ImageInfo (LayerInfo) or in Image Command Tool (Image Metadata Editor in 2010), then use the IMAGINE MrSID Encoders. Voilà you have a true transparent background data.

ERDAS will make the correct transparency creation ability more prominent and flexible in a future release.

Here is one big thing to remember; ERDAS uses 0 as the transparent value while ESRI uses 255. ERDAS as well as other remote sensing and photogrammetric packages have a black background page while ESRI has a white background page. The more careful image providers now create 8-bit data with a range from 1 to 254 rather than 0 to 255. All 0 and 255 values will be outside of the actual image footprint. This approach allows their customers to be flexible with whatever package they they are using at the moment.

MrSID Performance on MosaicPro and more....

ERDAS has researched, researched, tuned and tuned.... now we are processing 3982 MrSID DOQQs (all the state of Georgia, USA) into one seamless mosaic. The memory usage does not exceed 1GB at any point. We did not get an exact time, and file size.... but it took about 3 days and produced a >700GB output file.

3982 is NOT the maximum number, just the largest number we have tested. The steady memory usage indicates the maximum number is much, much higher than 3982.

One thing to note..... There is a bug in Microsoft's XP x32 operating system affecting very large file creation. Our conversations with Microsoft have lead to the conclusion the bug was introduced between XP SP1 and XP SP2. The bug keeps the operating system from supporting very large files. The maximum file size you can create depends on your system configuration. The largest we have heard of is 70GB. Most systems cannot exceed 35GB.

We have tried rolling back the XP operating systems back to SP1, or back to the original Windows XP, but that has not been successful. Once Windows XP SP2 is loaded, something is not being unloaded. This is a puzzle for both ERDAS and Microsoft.

What is the solution for large file creation in ERDAS IMAGINE 9.3.x? Use Windows XP x64 or Windows Vista. ERDAS will expand operating system support for ERDAS IMAGINE 2010, the versions to be announced later.

** A post-post clarification, if I may. I received a few emails concerning the XP x32 file size limit. This limit is not related to any specific file format. Rather, it is limited to the operating system not allowing the creation of a single large file of any type. Again, there are some variations, but if you need large files of any type you must move from Windows XP x32. For all its bad press, Vista x32 does not have this problem.