Re: Importing a large image...
- To: mathgroup at smc.vnet.net
- Subject: [mg98658] Re: Importing a large image...
- From: David Bailey <dave at removedbailey.co.uk>
- Date: Wed, 15 Apr 2009 05:01:55 -0400 (EDT)
- References: <email@example.com>
David Reiss wrote: > So, my fellow denizens of the group. > > I have a very large TIFF image--roughly 700MB in size. > > Its dimension are 43201 by 15601. It is single color with a bit depth > of 8. > > Mathematica is unable to Import this file on my 6 GM RAM powerbook > without maxing out the memory. > > I actually do not need to read in the whole file: I'd be happen with > being able to break the file into a number of smaller TIFFs which tile > it completely and then process each on independently (I am needing to > act on the data in various ways to yield a processed result for > further analysis down the line). This is all for a larger project > for a consulting client of mine. > > Any suggestions for how to programmatically carve up the image without > having to completely read it in first? I am looking for quick > solutions rather than ones that require a lot of programming. Either > it can be done pretty simply, or (more likely) Mathematica chokes on > these very large files. > > (Photoshop, on the other hand, does not choke on it at all, nor do > some other programs that are optimized for image analysis such as ENVI > (http://www.ittvis.com/ProductServices/ENVI.aspx): but I don't want to > work with these... nor do I have them....) > > Of course this leads to a suggestion for the Import function: to allow > reading in only a part of an image at a time. > > Feel free to respond to the list, but also CC me on the replies so > that I get them sooner than the usual turnaround. > > Thanks! > > --David > TIFF format is uncompressed (at least in practice), so I think you could write code using binary I/O, re-positioning the stream as necessary to read a block out of a larger image. Note that there is a big/little endian flag at the start of the file. Alternatively, you could perform the same operations in Java, using J/Link to communicate the results to Mathematica. Of course, using a 64-bit machine (and operating system) with sufficient memory, it would be probably be possible to use Import in the normal way. David Bailey http://www.dbaileyconsultancy.co.uk