WANTED: 16-bit grayscale and 48-bit true-color images 
Author Message
 WANTED: 16-bit grayscale and 48-bit true-color images


> The PNG group is busy testing various combinations of filters, interlacing
> and compression, but we really could use some real-world images with 16-bit-
> per-sample color depth (grayscale and RGB; images with alpha channel are OK,
> too).  So far our test corpus has a good number of regular 24-bit true-color
> and 8-bit (or less) color-mapped images, but we need some with 16 bits per
> color.  (We have considered creating 16bps images out of 8bps ones, but they
> would be extremely small and not necessarily representative of real 16bps
> images).  Some 12-bit medical images would be nice, too.

> If you either (1) have some, (2) have some way to generate them, or (3) have
> a pointer to some somewhere on the net, please send me e-mail with details
> (assuming you're willing to donate a few for testing purposes only).  We can
> probably deal with most reasonable formats.  (PGM/PPM would have been pref-
> erable if they supported 16bps in binary mode, but they don't.  Oh well.)

> Btw, for those in s.a.f and s.m.* who don't know what PNG is:  it stands for
> "Portable Network Graphics" (or, unofficially, "PNG's Not GIF") and will be
> a lossless replacement for the GIF format with support for up to 16-bit color
> depth.  The compression method is deflation, the same as in Zip/PKZIP and
> gzip.  (Completely mindless tests of color-mapped images with LZW [GIF] vs.
> deflation shows 10% improvement in compression even without any special fil-
> ters.  I don't have any numbers to compare with lossless JPEG.)

> Note follow-ups.

> Greg Roelofs
> Info-ZIP and PNG group

16 bit (12 bit) radiologic image are available by anonymous ftp at:


They are in DICOM format. But you can just bypass the header by calculating
the image dimensions (eg, header = filesize - (xdim * ydim * 2)). Byte order
is little endian.

CTs are 512x512, MRIs are 256x256. I wouldn't mess with the CR (computed
radiography) or digitized radiograpbs unless you need to work with very large

Department of Radiology, SB-05   |  voice (206)543-3320
University of Washington         |  fax   (206)543-6317
Seattle, WA 98195                |

Sun, 03 Aug 1997 09:29:55 GMT
 [ 1 post ] 

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