[R] ISO Eric Kort (rtiff)
cgw at witthoft.com
cgw at witthoft.com
Tue May 4 18:11:31 CEST 2010
Thanks, Brian. I can see where to mod readTiff to return the original data ranges; and where to mod writeTiff so it writes files with something better than the current 0:255 resolution range.
I have found an additional problem with readTiff, so is there someone I can write to about it?
What I found was, for some tiff images created within my company, readTiff does not convert the source data correctly. The files contain greyscale data, 16 bits per pixel (i.e. 0 to 4095). Whether it's a mistake in the way the tags were originally written to the file, or a mistake in the way that readTiff interprets the libtiff outputs, I don't know, but readTiff only reads the upper byte of each pixel. This produces data with a range of 0 to 15 (prior to being autoscaled into pixmap's [0,1] space ). I can dig up the values returned by tools like tiffdump, so if someone out there in R-help land can point me to the pertinent values, I'll do all I can to help solve this problem.
May 4, 2010 01:46:05 AM, ripley at stats.ox.ac.uk wrote:
On Mon, 3 May 2010, Carl Witthoft wrote:
> I wanted to ask Eric a question or two about the rtiff package, but his
> listed email address bounces w/ 550 error. Does anyone know how to reach
> him, or whether he's actively maintaining rtiff?
He is not. The latest version of rtiff was done by the CRAN team to
fix a number of errors and keep it building on the CRAN platfoms --
you will see it was packaged by me.
> If anyone's interested, my primary desire is for rtiff (or other tool) to
> provide me with the raw range of pixel values in a tiff file. rtiff dumps
> straight into a pixmap object, so the data are autoscaled into [0,1] .
It is very simple package, easy for you to modify -- this could be
done in readTiff in a couple of minutes.
An alternative is BioC package EBImage (provided your ImageMagick
installation supports TIFF).
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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