slow 2d image generation

hello group

first off, many thanks to all who helped with my previous question regarding 
constant maps...however, i now have a new problem...

the application i am currently developing with visad has a feature to load and 
display 2d image data from an ascii file...i am using the textadapter class to 
read the file and turn into a flatfield...the ascii file is in the tab-spaced 
format that the textadapter class can is a snip of the first five 
lines of an example ascii file:

Down_Range      Cross_Range     RCS
-755.383        -755.383        -124.0984508
-731.684        -755.383        -124.0586397
-707.986        -755.383        -123.995843
-684.288        -755.383        -123.9096856

...and so on

in this case, 'down_range' maps to the x-axis, 'cross_range' maps to the 
y-axis, and 'rcs' maps to an rgb value...everything loads and displays fine, 
but there are three major problems:

1) loading the data is ___sloooow___...the example file i snipped above comes 
to 147515 bytes (256 x 256 image size) and it takes a solid 30 seconds from 
when the file is opened to when the image is finally displayed...we have c++ 
code in other applications that loads and displays the same data almost it a java problem? it visad? it something i'm doing 

2) panning and zooming of the image (and line plots for that matter) are slow 
and choppy...when data is rendered as points, these functions are very quick, 
smooth, and there any way to speed up panning/zooming?

3) is there any way to increase the resolution of the image rendering to make 
it more 'smooth'?...right now it looks textured...when zoomed in closely, the 
data points look very triangular...any ideas?

thanks in advance for any help that can be provided...let me know if you need 
more information from me...peace!