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Hi, I can't replicate this on my laptop (mac os x). Instead, it works as expected - if I create a binary mask and then do the type conversion I still have the mask intact. AFAIK avwmaths does not use division but simply casts the values to the required type in the ususal c++ way. Here is what I did: i) load in avg152 in fslview and create a binary mask, save this to [Josi:~] avwhd avg152T1_brain-mask.nii.gz filename avg152T1_brain-mask.nii.gz sizeof_hdr 348 data_type INT16 ... This is a binary file: [Josi:~] avwstats avg152T1_brain-mask.nii.gz -r -R 0.000000 1.000000 0.000000 1.000000 When using avwmaths++ to convert the file [Josi:~] avwmaths++ avg152T1_brain-mask.nii.gz test -odt char it remains a binary mask [Josi:~] avwstats test -r -R 0.000000 1.000000 0.000000 1.000000 and has the desired type [Josi:~] avwhd test filename test.nii.gz sizeof_hdr 348 data_type UINT8 ... I guess we need to investigate - what platform are you running this on and did you compile yourself? cheers christian On 25 May 2007, at 14:57, Alle Meije Wink wrote: > I tried this on a segmented brain mask image (value 0/1): > > avwmaths++ segmented.nii segmentedBYTE.nii -odt char > > after which segmentedBYTE.nii was zero everywhere, and > > avwmaths++ segmented.nii -mul 256 segmentedBYTE.nii -odt char > > after which the values that were 1 in segmentedBYTE.nii were 0 > outside the mask and 1 inside teh mask. > > In other words: this is a way to make it work, but I'm not sure > that this is correct! How many users expect the values in their > images to change when they do a type conversion? > > Best > Alle Meije ____ Christian F. Beckmann University Research Lecturer Oxford University Centre for Functional MRI of the Brain (FMRIB) John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK. [log in to unmask] http://www.fmrib.ox.ac.uk/~beckmann tel: +44 1865 222551 fax: +44 1865 222717