Archive for the ‘Free (Libre) and Open Source Software (FLOSS)’ Category
The EXIF data in a JPEG has a field which is interpreted as pixels per inch. The standard requires this to be a positive number, not zero or blank, and by default it will be 72. This doesn’t actually equate to anything, now, and may never have reflected any real display.
Canon therefore set it at 72 in their cameras, Kodak appear to set it at 240, Nikon at 300.
Using an EXIF editor – exiftool for instance or the properties dialogue in the the image editor program I use – the gimp – to set that number to 42 or 976 doesn’t affect anything except that number.
If you want to print a 10 inch wide image, and you want it to have 300pixels per inch, then you’ll need 3000 pixels, which compared to the 5000 available across my EOS 7D full resolution images is no problem.
There does seem to be a pitfall – if you are using Adobe Photoshop and leave an option “Resample” checked in the size dialogue, the program will take your nice 5000 pixel image and merrily turn it into a 720 pixel image or otherwise screw it up.
So – top tip: Uncheck the “resample” box.
 There are two fields, for X axis and Y axis resolution. We expect them to be the same on a camera.
VistA on GT.M http://www.modernhealthcare.com/article/20120116/BLOGS02/301169914 and http://medsphere.com/news/885-Kern-Medical-Center-Awarded-Federal-Funds-for-Meaningful-Use-of-OpenVistar-Electronic-Health-Record
See also http://openvista.org
Which given the studious lack of central planning and control of its development is interesting.
Its fundamental principle may be worth adopting. NPfIT started from 0/2 on that basis, and if anything got worse.
So the internet works by providing wires on which sit a load of computers (referred to as “hosts” or “peers” ). Each can talk to each using a simple set of rules. Some vaguely central directories of machines are kept, and anyone may make a list of machines they trust and identifiers for them. This is a task which governments could do well, if they could do it well.
If the computer in the casualty department wants to know something about a patient, then it can send a question to the computer in the patient’s general practice. It could ask around to the Darzi Centre, the Nuffield, and the Orthopaedic clinic in Val Thorens as well.
And then the patient should get an account showing what access has been made to their medical record, which tends to keep everyone honest, or at least visible.
(Adding a registry and security to this is not as hard as it may seem. Not trivial, and not something to do with secret programs, but the problems are known)
 After Al Gore steered funding for it through Congress the nerds just got on with making it work.
 Correlation does not prove causation
 Rough consensus and _running code_
 I mean is, but this is supposed to look more tactful
 An indication of the attitude which works, and prevails, and is opposite to that favoured in NPfIT thinking, where _our_ machines are regarded as clients of _their_ servers
 examples of places excluded by the currentfailed and abandoned approach to NHS sharing of records.
 whatever a medical record is, something which Accenture, Fujitsu, and CSC turned out to be no more sure about than the DoH, I think. I’m not sure about it either, but I’m quite keen on saying so because I think it is interesting to consider.
 refer to note 7 if you want to demonstrate having paid attention
 Some people may say understood and solved, but at least the latter group tend to be selling secret source programs that they claim solve them. The former group may be optimistic, but are likely to say that closed source solutions are unreliable, and are correct in that.
Dr Dr Geraint Lewis of the Nuffield Trust on VistA, which is a good thing.
Formatting the card will not remove pictures in most cases, and is not reliable for removing all of them. Deleting the images from the camera or the card doesn’t conceal them either. (Canon offer an option described as “deep formatting” or low level formatting, which quite slowly initialises each memory location on the card. The standard “formatting” operation simply erases the file attributes table, the pointers to files on the card. (edit))
Recovery from erase or a simple “format” is very easy, anyone finding a card will have no difficulty at all getting software to read the card byte by byte, and reassemble image files.
Someone who stole a card with the intention of embarrassing a doctor or looking for gain from images – not a large threat, actually – could be relied up on to be certain to recover any images.
I tried recoverjpeg on a 4GByte card which has been used and “erased” – IE files unlinked from the directory entry pointing to them – many many times, and new files recorded – and it retrieved 496 files. A sample of them were complete, I suspect that all of them, and certainly all recent ones, are undamaged.
Memory cards arrange that files are written to new areas of card rather than to previously used ones, so as to even out wear on the memory locations, to increase the life of the card. This opposes secure deletion.
To securely remove pictures from a 4 GByte card, the only approach which certainly succeeds is to actually write a value to each memory location on the card. This will hide previous information to a degree which would require at least research lab or national security facilities to recover.
It isn’t difficult, technically, and essentially involves writing a stream of say 4GBytes of zeroes or arbitrary patterns to the device, rather than to files on the device. In Linux dd will do it.
Copying files across would be more tedious, but if the card is filled with data and then reformatted it will reasonably secured.
Not losing the thing is a key point, however cameras, particularly shared ones in open buildings, are prone to being stolen, as are loose cards. Securing the cards used for patient photographs in the building, and substituting a different card when the camera goes outside is worth considering.
An alternative would be to not use a card, and operate the camera “tethered” to a computer.
recoverjpeg is licenced under the GNU GPL, you can use it freely.
Item 17 of the advice given at the RD&EH Trust Dermatology department website is wrong. I’ve told the author and it has remained wrong.
Recursive Google search on this: http://www.google.com/search?ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=1&q=exeter+clinical+photography
If you search Google for the specifically wrong phrase “
Format instead of deleting is recommended as it will increase the life of the camera card and ensure the image is completely deleted” then the next item on the first page carries on with the rest of the necessary advice “and then shoot random images until the card is filled”.
Nearby on the same page Lexar’s tips for card use mention using their secure erase option, and warn users that “Remember that when you’re deleting an image, you’re only deleting the file name and other related information pertaining to the image-not the actual image itself. This is why you can still recover the image once it is deleted, since the data area where the image is stored remains intact.”
Everyone makes mistakes, often in print, and not uncommonly in advice being given as from authority. What is alarming is when the mistake is defended instead of being corrected, and when the management culture of the organisation does not discourage this. If small easy faults are deliberately preserved, it is plausible that large difficult faults are nevertheless tackled with speed and vigour, but if an organisation and its people show that it will not leave small errors persisting then its claims to tackle important problems gain an increment in reliability. NASA and their contractors’ zero defect program (they spell it that way) and the Kaisen approach favoured by Toyota and many others are good illustrations of the line of thinking involved.