Re: Can NCL be used to generate RGB composites?

Thanks David,

> Sorry for the delay answering this message. This is actually a very
> pertinent topic and is one of the underlying motives for our addition
> of new output workstations based on the cairo 2d graphics library.
> More about this in a moment.
>
> There is currently no way to directly display 3 channel RGB images in
> NCL. NCL uses an indexed color model with a maximum of 256 colors.

I was beginning to conclude this myself; it is good to have it confirmed so I know I didn't just overlook something.

> You could display a 3-channel image as a raster or cell-filled contour
> plot using the following steps:
>

Thats a clever work-around but I suspect its going to be hard to get the sort of image quality I was looking for via an 8 bit colour map. Thanks for taking the time to work through this example though.

I already have capability to produce good quality images as TIFF / PNG etc but was looking for a way to add coastlines and grid lines. NCL appeared attractive since we already use it for a number of other image products, but I think that, for this application, I'd be better looking for an alternative solution (since the image quality is important).

>
> Once the Cairo workstations are in place, we will be implementing a
> new (but backwards-compatible) direct color system that will eliminate
> the need for color tables for RGB image graphics. We expect to
> implement an ImagePlot object that will allow for fast high-quality
> rendering and geolocation of a number of standard image formats
> (including especially PNG and TIFF). Hope this helps.

This would definitely be good. How far away do you think this is?

Simon

--
Simon Wood
Scientific Programmer
National Institute of Water & Atmospheric Research Ltd (NIWA)
Wellington, New Zealand.
http://www.niwa.co.nz
NIWA is the trading name of the National Institute of Water & Atmospheric Research Ltd.
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