Re: Image Processing

*To*: mathgroup at smc.vnet.net*Subject*: [mg66110] Re: Image Processing*From*: David Bailey <dave at Remove_Thisdbailey.co.uk>*Date*: Sat, 29 Apr 2006 03:41:21 -0400 (EDT)*References*: <e2srgo$3bv$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Charlie Springer wrote: > Hi all. > > Old physicist, new Mathematica user. > > I want to perform 2D FFT's on images. I have used Import to get a JPEG into > apparently, a graphic object. I can not see how to get it into a "list of > lists" or any form acceptable to Fourier[]. > > Anybody have a snippet or some experience? I'm still learning the > terminology. If this works out I'll get the grid version for a Mac Quad. > > -- Charlie Springer > Hello, When you import a JPEG file you end up with a Graphics object, whose structure is suppressed for convenience by the FrontEnd, but it is easy to examine, taking care not to spill a super large set of numbers into the notebook: image=Import["something.jpeg"]; image//InputForm//Short Graphics[Raster[{{{73, 54, 0}, {72, 53, 0}, {<<3>>}, <<96>>, {55, 37, 1}}, <<34>>}, <<3>>], <<3>>] So image[[1,1]] is a 2-D array of colour triples - which you can boil down to a single number (e.g. by summing them to get a gray scale) and apply the Fourier transform. Note that although other types of images - such as GIF - import as a Graphics structure, the internal structure is not the same (but there are some GIF-specific Import options to solve this if you require them). David Bailey http://www.dbaileyconsultancy.co.uk