[fitsbits] Re: FITS vs. TIFF (or other image formats)

[Paul Schlyter]

In article <Pine.OSF.4.30.0111191850410.5017-100000 at poseidon.ifctr.mi.cnr.it>,
Lucio Chiappetti  <lucio at ifctr.mi.cnr.it> wrote:
>On 19 Nov 2001, Paul Schlyter wrote:
>
>> Rick Armstrong <careful at times.com> wrote:
>>
>> > 1) Why do astronomers use FITS, instead of just writing huge TIFFs or files
>> > of some other format?
>>
>> FITS is a general data storage format, not just an image format.  A TIFF
>> file can only store images -- a FITS file can store any kind of data.
>
>As I tried to answer personally to Rick Armstrong this morning (but the
>mesage was rejected because the e-mail address was wrong so I repeat it
>here), that's not the only reason, particularly from an historical point
>of view.
>
>Astronomers use FITS because that exists from more than 20 years, back in
>the magtape and mainframe era (including 16-bit, 32-bit, 36-bit, 60-bit
>machines which explain the otherwise funny 2880 byte record length !) and
>possibly pre-dates "all some other" formats.

Yep, I strongly suspected compatibility with arcane mainframes was
one of the major reasons for FITS.  THanks for clarifying this further.

>Astronomers use FITS because they are interested in the exact measure
>content : even in FITS images (at the beginning all FITS files were images
>... hmm or random groups, but I never used random groups) each pixel is a
>measure. Most other image formats are mainly interested in the look.
>
>For instance some of them use lossy compression algorithms (JPEG I
>believe), which could never be acceptable for an astronomer.

True, however there are plenty of image formats with non-lossy
compression algorithms.  For instancs GIF and TIFF.  But again they
are image formats, not general data storage formats.  And they also
assume a byte is 8 bits, which isn't always the case (or perhaps I
should say wasn't the case; nowadays computers with a byte length
different from 8 bits are getting rarer and rarer - perhaps they're
already practically extinct).




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