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VIEWFITS.DOC
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ViewFITS : FITS viewer for OS/2 PM.
-----------------------------------
Current status: Version 0.3, release 2, August 3, 1993
THIS VERSION (0.3, R2) IS FREEWARE, YOU CAN GIVE IT TO OTHER PERSONS WITHOUT
ANY FEE. YOU MUST GIVE IT IN THE SAME FORM, I.E. WITH THE SAME FILES, AS YOU
RECEIVED IT. USE IT AT YOUR OWN RISKS. THE AUTHOR IS NOT RESPONSIBLE FOR ANY
DAMMAGES OR MISINTERPRETATIONS OF THE DATA HANDLED WITH THIS PROGRAM.
Introduction:
------------
ViewFITS is a FITS viewer for the OS/2 PM. "FITS" stands for "Flexible
Image Transport System", a standard in use for many years by professonials.
ViewFITS, in the current version, can display images of any format, 8 to 32
bits per pixel, integers or floating points. The colour palette (LookUp Table)
can be easily modified to help the user to get the maximum of the image. Let's
see the principal characteristics.
Handling data:
-------------
In the present version, new image can only be got via menu (FILE/NEW).
In a future release, we project to make the application be able to
read arguments on command line and use pipes to communicate with other
programs. It will then be used as a "client" program.
The colour palette:
------------------
The colour palette, or lookup table, contains 64 colours. They are scaled
via a linear equation. So, the user can modify the contrast and the
brightness of the palette to customize the display as s/he wants. Negativation
can be do as well. In all cases, data are processed to be spread over all the
dynamic range of the palette:
e.g.:
Your image has pixels with values from 100 to 300, so the dynamic range is
200. The intercept of the image is then Ii=100 and the slope is given by
Si= (number of colour) / (dynamic range) = 64/200 = 0.32.
This way, each a pixel is drawn, its colour is Cp=(Vp - Ii) * Si. Let's
imagine we have Vp=150, Cp = (150 -100) * 0.32 = 16. Pixels with Vp=100
will get Cp=0 and Vp=300, Cp=63 (not 64!) where Cp is the colour index, i.e.
the position in the lookup table.
The menu PALETTE allows the user to modify the contrast and the brightness of
the lookup table. This way, a given pixel will always have the same colour
index but the corresponding colour value will change.
The PALETTE menu allows the user to do negativation too.
Zooming:
-------
The zoom option on the menu allows the user to zoom in or zoom out the image.
Each zooming modify the scaling factor by a factor of 2.
Known bugs:
----------
Here is a short list of know bugs:
1- There is an error in the palette manager (I have nothing to do with this).
If you have a window that modify the palette over the image, the palette
won't be restored once the window has moved. To correct that, use REFRESH.
( It seems to be fixed on OS/2 2.1 GA. )
2- Because it use palette manager, this application cannot be used under OS/2
2.0. It only works under version 2.1 beta and 2.1 GA.
3- When zooming, it is not possible to see a hidden part of the image. It
will be fixed soon.
Improvments since last release:
------------------------------
1- A bitmap is now used insteed of direct drawing to the screen. Faster!
2- Zooming in and out is possible.
3- Now, the data are displayed in the right sense, up is up and down is down.
4- Before, a direct memory acces in the program caused a protection violation
and an exit to the system. Now it has been fixed.
Unknown bugs:
------------
I'm waiting for your reports! You can join me via e-mail at
beaucham@phy.ulaval.ca
or on the FIDONet forum "astronomy echo".
VERSION 0.3, is FREEWARE.
Dominique Beauchamp
Quebec City
August 3, 1993