VisionTek SVSLIDE format

[Benjamin Gilbert]

On 10/27/2013 01:35 AM, Donald Regula wrote:
> The first three rows of the unique table hold the [id]:
> ++MagicBytes
> ++VersionBytes
> Header

The Header row contains a binary structure.  The first 12 bytes are 
32-bit little-endian numbers which appear to contain the tile size and 
image width and height in pixels.

> There are two typical sort of rows in the unique table:
> a "data" row with a unique id, containing an image tile
> a paired row (of unknown significance) with the same id, suffixed with
> an "#" character (e.g.- T;2048|47616;1;2;0 ) .

The "#" cleverly stands for "hash".  The row contains the MD5 hash of 
the corresponding tile data.

> The id column is comprised of five fields separated by a semicolon[;].
> [id] T;2048|47616;1;2;0
> [1] T : apparently indicates "Tile"
> [2] 2048|47616 : are the row-index|column-index (in pixels)
> [3] 1: the pyramid level {1 is the highest resolution (e.g.- scanned
> with 40x objective), other resolutions are 2, 4, 8, 16, 32, 64, 128,
> with 256 being a thumbnail smaller than a single tile}
> [4] 2: the monocolor {0=Red,1=Green,2=Blue)
> [5] 0: unknown (always zero?)

True, but I suspect the id column values are intended merely as unique 
identifiers, and that the application is not intended to construct them 
directly.  There's another table called "tile", which contains all of 
the same information broken out into separate columns, plus a foreign 
key to the id column of the unique table.  There's also a "tileview" 
view joining the tile table to the image data in the unique table.

Unfortunately, the tile table is devoid of any useful indexes for 
lookups, and the tileview is too slow to use.  But it's reasonable in 
our codebase to read the entire tile table into RAM.

===

Initial support for svslide has been committed to Git master.  Give it a 
try and let me know how it works for you.  If you're on Windows, you can 
get a snapshot build from:

     http://openslide.cs.cmu.edu/download/snapshots/windows/

Thanks,
--Benjamin Gilbert