Hi David, If the data compression is carefully chosen you are right: lossless jpeg2000 compression on diffraction images works very well, but is a spot slow. The CBF compression using the byte offset method is a little less good at compression put massively faster... as you point out, this is the one used in the pilatus images. I recall that the .pck format used for the MAR image plates had the same property - it was quicker to read in a compressed image that the raw equivalent.
So... once everyone is using the CBF standard for their images, with native lossless compression, it'll save a fair amount in disk space (=£/$), make life easier for people and - perhaps most importantly - save a lot of data transfer time. Now the funny thing with this is that if we compress the images before we store them, the compression implemented in the file system will be less effective... oh well, can't win em all... Cheers, Graeme 2009/9/18 Waterman, David (DLSLtd,RAL,DIA) <david.water...@diamond.ac.uk>: > Just to comment on this, my friend in the computer game industry insists > that compression begets speed in almost all data handling situations. > This will be worth bearing in mind as we start to have more fine-sliced > Pilatus 6M (or similar) datasets to deal with. > > Cheers, > David. > > -----Original Message----- > From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of > William G. Scott > Sent: 17 September 2009 22:48 > To: CCP4BB@JISCMAIL.AC.UK > Subject: [ccp4bb] I compressed my images by ~ a factor of two, and they > load and process in mosflm faster > > If you have OS X 10.6, this will impress your friends and save you some > disk space: > > % du -h -d 1 mydata > 3.5G mydata > > mv mydata mydata.1 > > sudo ditto --hfsCompression mydata.1 mydata rm -rf mydata.1 > > % du -h -d 1 mydata > 1.8G mydata > > This does hfs filesystem compression, so the images are still recognized > by mosflm, et al. I think they process a bit faster too, because half > the information is packed into the resource fork. > This e-mail and any attachments may contain confidential, copyright and or > privileged material, and are for the use of the intended addressee only. If > you are not the intended addressee or an authorised recipient of the > addressee please notify us of receipt by returning the e-mail and do not use, > copy, retain, distribute or disclose the information in or attached to the > e-mail. > Any opinions expressed within this e-mail are those of the individual and not > necessarily of Diamond Light Source Ltd. > Diamond Light Source Ltd. cannot guarantee that this e-mail or any > attachments are free from viruses and we cannot accept liability for any > damage which you may sustain as a result of software viruses which may be > transmitted in or with the message. > Diamond Light Source Limited (company no. 4375679). Registered in England and > Wales with its registered office at Diamond House, Harwell Science and > Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom > >
