[R] Digital Image Processing

[Roger Bivand]

On Fri, 13 Feb 2004, Robert W. Baer, Ph.D. wrote:

> I have seen several posts (but few answers) in "R-help search" as to
> whether there are any packages that use R to process digital images.  
> There are several categories related to the general type of problem that
> are useful to know about: -- Any existing packages for taking a digital
> image format {any flavor like TIFF, jpg, png, or GIF (or even TWAIN
> input)} and representing it internally in R as RGB or HSB arrays? -- Any
> existing packages for taking array representations of an image and
> representing it "graphically" as a "bitmap" (colored?) image in an R
> window? -- Any digital filter, image (signal) processing packages
> specifically directed at "image processing" or computer vision sorts of
> problems?

The basic package is pixmap, which reads PNM files on all platforms, and 
converts them to new-style class "pixmap" objects, which are arrays. It is 
not efficient, because each pixel is represented by a double in each band, 
but can be used as a structure to start with.

Beyond that, for reading other formats (including subscenes of other 
formats), rgdal uses the GDAL abstraction library, and can deliver 
pixmaps, or raw vectors of band data, which can also be displayed. Because 
rgdal depends on external libraries, it is not distributed compiled for 
Windows.

Several of the medical image analysis packages also include i/o and 
display functions suited to the data formats they use. 

One (minor) drawback to working with images is that displaying large 
images can tax the graphics output functions, where the basic model is 
vector graphics, but as with all things here, ideas and contributions can 
make a difference. Certainly for prototyping, there should be quite a lot 
of potential.

Roger

> 
> And perhaps the question I should have asked first,  is it silly to think that R might be a useful tool for exploring (prototyping solutions) to image processing problems?
> 
> Thanks for any insights,
> Rob Baer
> 
> 
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-- 
Roger Bivand
Econonic Geography Section, Department of Economics, Norwegian School of 
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen, 
Norway, voice: +47-55959355, fax: +47-55959393; Roger.Bivand at nhh.no