[Kst] KstImage limitations for healpix plotting

[Ted Kisner]

Hello everybody,
  
I've been thinking about some potential problems with the current planned 
scheme of:

healpix_datasource --> KstMatrix --> KstImage
                   \--> KstVectors --> KstVectorfield (to be created)

I was wondering if anyone had ideas of how to implement the following within 
this scheme:

1.  I need to create arbitrary axes.  Let's say that the datasource has been 
configured to return a matrix containing a sinusoidal projection.  The axes 
on the top and bottom of the graph will be different from each other, and 
from the Y midpoint (the PHI min/max at the midpoint sets the projection).  
Now let's say that the user zooms in to a region of the map.  The axes must 
change based on where the zoom rectangle lies, and the type of projection. 

2.  In a map of the sphere, pixels may be empty (set to a certain null value 
== -1.6375e30).  It would be useful to plot all these pixels a uniform 
background color, rather than the lowest color of the current palette.  Also, 
these pixels should be ignored for the purposes of autoscaling.

I'm beginning to think that these may be easier to accomplish if I do 
something like this:

healpix_datasource --> KstMatrix + KstVectors --> KstHealpix (to be created)

The logic is that if I have to create a new basecurve anyway, perhaps healpix 
data is "different" enough that it warrants its own display type.  Also note 
that all the necessary healpix code is already in kst- it would just need to 
be moved to a library so that both the datasource and the new basecurve could 
access it.

Any thoughts / comments?

-Ted