[fitsbits] Question(s) regarding development of proprietary FITS manipulation software. . .

[Michael Williams]

Alright, I've looked at RFC 4047, and I'm not much better off.  I  
have about 6 (and I'm sure that's not even the tip of the iceberg)  
valid FITS files all formatted completely differently.  The only  
thing that's consistent among them are the top of the headers.  Some  
choose their own "keywords" others have a million "COMMENTS".  I  
suppose, for time's sake, what I need now, are the most common  
"formats".  Can someone send me (offline or otherwise) some sample  
data with accompanying comments/markup regarding what each piece of  
data means?  A few examples of what I currently have are:

FITS compliant header followed by. . .

1) binary data
2) non-compliant header-like text
3) array's of numbers

. . .and the list goes on.  Any help would be greatly appreciated.   
And thanks again for your help thus far.


Regards,
Michael


On Aug 21, 2007, at 10:36 AM, William Thompson wrote:

> Michael:
>
> Formats like GIF and JPEG are designed such that the images are  
> scaled into the 8-bit 0-255 range used by computer displays, and  
> are generally accompanied by color information, such as color  
> tables or separate red-green-blue images.  As such, they are  
> already prepared for direct imaging.
>
> The data in FITS files, however, are generally not preprocessed for  
> viewing. They are in the units needed for scientific analysis.   
> Such images usually need some additional processing in order to be  
> easily viewed.  The simplest way to process the image is to rescale  
> it, mapping the minimum value to 0 and the maximum value to 255.   
> That often works, but usually one has to tweak it to get a good  
> image.  These are some examples of the kind of operations that a  
> general FITS viewer would need to be able to do:
>
> 1.  Adjust the mapping from image values to displayed intensity, to  
> zero in on the most significant range of values.
>
> 2.  Apply a variety of color tables to the data, and adjust the  
> gamma of those color tables.
>
> 3.  Display the logarithm of the data.  I've also found it useful  
> to display the Nth root.
>
> Unfortunately, there's no right answer that covers all situations.   
> It really depends on the data.
>
> Bill Thompson
>
>
> Michael Williams wrote:
>> Maren,
>> I understand that.  But many of the sample FITS files we've been   
>> given have ASCII data in a header, then literally an accompanying   
>> "picture"; unless, of course, it's simply a matter of the  
>> programs  we're using automatically interpreting the "picture".   
>> Is this  incorrect?  Our concern is how to properly display the  
>> "picture" and  what relationship it has to other "picture" formats.
>> If it's not a picture, then what is it *exactly*?  Simple plots  
>> of  data?  How is it to be interpreted?  We've got a TON of data   
>> regarding what FITS is supposed to be, but nothing regarding the   
>> actual interpreting of data.
>> Any suggestions you have would be greatly appreciated.
>> Regards,
>> Michael
>> On Aug 20, 2007, at 5:49 PM, Maren Purves wrote:
>>> Michael,
>>>
>>> it's not graphics, it's data.
>>> Well described reducible data.
>>> You can't get much physics out of just images.
>>>
>>> Aloha,
>>> Maren
>>>
>>> gberz3 wrote:
>>>
>>>> Thanks Maren.  One question I suppose I've just forgotten to  
>>>> ask:  Is
>>>> there anything particularly special about the actual graphics  
>>>> content
>>>> of a FITS file?  Or is it perhaps simply a glorified TIFF or  
>>>> JPEG of
>>>> some sort?
>>>> Regards,
>>>> Michael
>>>> On Aug 4, 11:09 pm, Maren Purves <m.pur... at jach.hawaii.edu> wrote:
>>>>
>>>>> On Fri, 3 Aug 2007, gberz3 wrote:
>>>>>
>>>>>> So far, I've really only looked at the CFITSIO items and it's  
>>>>>> very
>>>>>> well documented (really too well) but the function names don't  
>>>>>> seem
>>>>>> very intuitive.  I'm sure they mean a lot more to someone  
>>>>>> familiar
>>>>>> with FITS, but I'm absolutely not.  It's basically like  
>>>>>> someone in
>>>>>> 1989 asking you to write a JPEG file manipulation program.   
>>>>>> Sure  the
>>>>>> information exists, but with 0 familiarity you'll need a lot  
>>>>>> of  input.
>>>>>
>>>>> there used to be a file called longnames.h ...
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>
> -- 
> William Thompson
> NASA Goddard Space Flight Center
> Code 671
> Greenbelt, MD  20771
> USA
>
> 301-286-2040
> William.T.Thompson.1 at gsfc.nasa.gov