From sla at ucolick.org Wed Jan 8 03:57:03 2003 From: sla at ucolick.org (Steve Allen) Date: Wed, 8 Jan 2003 00:57:03 -0800 Subject: [fitsmime] new version of Internet Draft for media types Message-ID: <20030108085703.GA4304@ucolick.org> There is a new version of the Internet Draft to register MIME media types for FITS along with new versions of the supporting documents now available at http://www.ucolick.org/~sla/fits/mime/ The US VO folks are currently engaged at AAS, and the European VO folks are preparing for a major demo later this month, and no formal action is going to happen until after they are ready to review things, so there is no rush to mull over the new contents. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 sla at ucolick.org Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93 From sla at ucolick.org Wed Jan 22 02:58:37 2003 From: sla at ucolick.org (Steve Allen) Date: Tue, 21 Jan 2003 23:58:37 -0800 Subject: [fitsmime] reaction to the draft? Message-ID: <20030122075837.GA2028@ucolick.org> The Internet Draft to register MIME types for FITS has benefitted from several good suggestions during the past few weeks. It is still at http://www.ucolick.org/~sla/fits/mime/ along with the ancillary documentation about the process. I hope to announce the draft to fitsbits/sci.astro.fits in a while as a general call for comments prior to beginning the formal proceedings to get clearance from the FITS community, prior to submitting the draft to the internet community. Reviews and comments about the draft from the VO community would be most welcome, for I remain concerned that the draft may not adequately address those needs. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 sla at ucolick.org Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93 From arots at head-cfa.cfa.harvard.edu Fri Jan 24 17:02:52 2003 From: arots at head-cfa.cfa.harvard.edu (Arnold Rots) Date: Fri, 24 Jan 2003 17:02:52 -0500 (EST) Subject: [fitsmime] reaction to the draft? In-Reply-To: <20030122075837.GA2028@ucolick.org> Message-ID: <200301242202.h0OM2qe15433@xebec.cfa.harvard.edu> Here are some comments. I must confess that I have not read all mail, so some of this may already have been discussed. Section 4.2: Should, I think, define a PHDU and point out its unique characteristics. This section also mentions table formats but should point out two unique properties of these tables: - the data may be in ASCII or in binary format - cells may contain scalars or (multi-dimensional) arrays (vectors) Section 4.3: Stability is also strengthened by the fact that many astrophysical archives store their data in FITS files. Section 5, first text paragraph: I suggest deleting the reference to SIAP: prototypes that may or may not survive do not lend any strength to the case for a permanent standard. Section 5.1, Additional information: Should define an "empty PHDU" Under what an applications SHOULD handle, it may help to explicitly mention tables. Most likely, this will be the bulk of the use for this MIME type, after all. Second example: Somehow, I'd like to give this more prominence since it is THE crucial archival format for all X-ray data. And one might point that it represents effectively a sparse time series as well as a sparse image, in most cases. Section 5.2, Recommendations for application writers: I'd suggest rephrasing the second, third, and fourth paragraphs: Note that an application intended to handle "image/fits" has significantly more responsibility than an application intended to handle, e.g., "image/tiff" or "image/gif". FITS image arrays contain elements which typically represent the values of a physical quantity at some coordinate location, rather than the rendering of those pixels. Consequently, they do not contain any rendering information in terms of transfer functions or color look-up tables. The application should provide this functionality, either statically using a more or less sophisticated algorithm, or interactive allowing the user various degrees of choice. In implementing the rendering functionality one should keep the following in mind: - The image values may be integers or reals; in some cases complex numbers - FITS provides for a mechanism to mark certain pixels as having indefinite (invalid) values - The dynamic range of the the pixel values may easily exceed that of the display medium and the eye; logarithmic, square-root, or quadratic transfer functions and histogram equalization techniques have proved helpful The data array in the PHDU of a file described as "image/fits" MUST have a dimensionality between 1 to 999, the boundaries inclusive, indicated by the NAXIS keyword. However, one should be aware that any coordinate axis in a FITS image may only be one pixel long. Hence a two-dimensional imaging application would be quite capable of displaying, for instance, a four-dimensional image (NAXIS=4) whith two degenerate coordinate axes of length one pixel. Three-dimensional images (NAXIS=3 without degenerate axes) are of special interest. Inspection of the World Coordinate System (WCS) keywords may indicate that one of the coordinates is time. Writers of applications intended to handle "image/fits" SHOULD consider presenting such an image in a fashion akin to that used for an animated GIF; however, they should consider offering the option of a time-lapse sequence display for all three-dimensional images since it is an effective technique for visualizing three-dimensional data. I hope this is constructive, - Arnold Steve Allen wrote: > The Internet Draft to register MIME types for FITS has benefitted from > several good suggestions during the past few weeks. It is still at > http://www.ucolick.org/~sla/fits/mime/ > along with the ancillary documentation about the process. I hope to > announce the draft to fitsbits/sci.astro.fits in a while as a general > call for comments prior to beginning the formal proceedings to get > clearance from the FITS community, prior to submitting the draft to > the internet community. > > Reviews and comments about the draft from the VO community would be > most welcome, for I remain concerned that the draft may not adequately > address those needs. > > -- > Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 > sla at ucolick.org Voice: +1 831 459 3046 http://www.ucolick.org/~sla > PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93 > _______________________________________________ > fitsmime mailing list > fitsmime at listmgr.cv.nrao.edu > http://listmgr.cv.nrao.edu/mailman/listinfo/fitsmime > -------------------------------------------------------------------------- Arnold H. Rots Chandra X-ray Science Center Smithsonian Astrophysical Observatory tel: +1 617 496 7701 60 Garden Street, MS 67 fax: +1 617 495 7356 Cambridge, MA 02138 arots at head-cfa.harvard.edu USA http://hea-www.harvard.edu/~arots/ -------------------------------------------------------------------------- From sla at ucolick.org Mon Jan 27 20:03:17 2003 From: sla at ucolick.org (Steve Allen) Date: Mon, 27 Jan 2003 17:03:17 -0800 Subject: [fitsmime] changes induced by Arnold Rots Message-ID: <20030128010317.GA14661@ucolick.org> I have modified the Internet Draft in response incorporating most of the suggestions from Arnold Rots. Several sections have become more general than they were, and the document is better overall. The changes do induce two new sets of questions to be posed here. First, the "Contributors" section now gives credit to many members from this discussions list. Please let me know if I have missed anyone or if anyone does not want to be listed. I am also unsure how formal the affiliations for everyone should be, and I suspect that I may have mistaken some of them. Corrections are most welcome. Second, the note from Arnold suggested that the tabular event lists which the high energy community uses to store sparse images deserved mention. I have added commentary to the draft which asks this: It would be kind of nice to add another paragraph which points at various documents that describe particular usages of FITS files which are commonly exchanged among various sub-disciplines of astronomy. For example, the binary table format used for photon event lists by high energy astronomy is described by http://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/events/ogip_94_003/ogip_94_003.html From my own experience I should be able to point at a document that describes various usages of putting CCD mosaic data into FITS files. Partly these would be examples of the unsolved problems of FITS semantics, but moreso they could be guides for implementors who might want to teach their applications to display more kinds of data. Are there other documents pertaining to various sorts of FITS usage which deserve to be mentioned here? -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 sla at ucolick.org Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93