Thursday, 28 October 2010

Appearances Deceptive

Another post, another screen shot. Almost looks like a real app :P

Differences are actually quite large though and quite a bit under the UI. An Sqlite3 database holds minimal patient, study and series info. Directories can be parsed for all their contents, recursively descending into sub-directories if desired. It's passably fast at parsing files and importing into the database too, at a bit over 1GB/min. That seems to be IO limited though as the CPU usage on my quad core peaks at about 10% much of which is system time. That will slow down as more data is inserted per file into the database so we'll have to see how bad it gets. Quietly pleased that it went through a lot of data without barfing once :)

The patient list does nothing but scroll and look pretty so far. The decoded file in the bottom right panel is one that was read independently of the database and patient list. There's no way to navigate to a file from the patient. Yet. Not least because individual files/images are not stored in the database yet...

I downloaded a whole bunch of the example files for Osirix only to discover they're mostly using the JPEG2000 transfer syntax. Arg. Vaguely fortunately, only the pixel data uses the actual JPEG2000 compression and the rest of the data is explicit VR little endian. Considerable staring at the standard and a hex editor, the addition of a new element decoding function (about 10 lines) and Hastur now reads all the metadata.

The pixel data itself is going to be a lot more trouble. It's actually held as an encapsulated document in the pixel data tag. The encapsulated document is a series of fragments encoded in a similar way to an SQ element. You can see the hex that delineates the individual fragments in the screen shot, the delimiter is "feff00e0". It won't be hard to write a parser to chew through the encapsulated document but since I don't have a JPEG2000 codec, that will wait.

Next up is storing files and images, linking bits of the UI together and figuring out the widget layout black art.

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