Talk:MrSID

Pyramid file format?

Is this just an implementation of the more generic Pyramid image file storage method where multiple resolutions of the same file are stored to speed processing time, display time, etc?

I am not an image compression technologist and know very little about the process. All I have is their tech sheet. Please look for copyright issues and expand on the encoding technique.

Mancomb 15:01, 7 October 2005 (UTC)

> Is this just an implementation of the more generic Pyramid image file

No, it is similar to JPEG 2000. The article (now?) contains a link to Wavelet compression, which explains it a little more. I'm no compression technologist, but I think the MrSID format can use decompress a subset of the data which results in a lower-quality (lower resolution) copy of the image with the benefits you describe. see also Set partitioning in hierarchical trees

- As I understand it is not a pyramid image, it just stores all wavelet components, and retrivies nacassary components. So it is much more like quad-tree of wavelets. It Have advantage, than normally pyramid image will need about 33% more space on disk. With wavelet based approach one can easly go down to about +5% percent of more space used (actually it can go down to 0%, but some indexing informations are naccassary to know where each wevelet level and block lies in memory). It is much more like progressive reffinment (similar like in JPEG, or much more like in PGF, by just using first few wavelet levels, you already have full image, but of lower quality, by selectivly using deeper level you can improve quality of any reqion of image you really need - this way you can easly store and view gigantic files at any zoom level). —Preceding unsigned comment added by 149.156.82.207 (talk) 16:24, 1 October 2010 (UTC)