| Re: Overlay multiple filled contour plots? [message #46209 is a reply to message #46208] |
Tue, 08 November 2005 23:48   |
peter.albert@gmx.de
Messages: 108
Registered: July 2005
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Senior Member |
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Hi Sarah,
if I get it right, after plotting the terrain height the ocean areas
are still black (or white, or whatever your background colour is),
which you'd like to change by plotting the landsea mask? Well, it might
be that David Fanning's image_blend routine might help
(http://www.dfanning.com/programs/image_blend.pro), but it is actually
more about overlaying images using transparency. Your point seems to be
not to overlay the terrain information but to cut out the ocean areas,
put a different information there and leave the rest untouched.
I'd suggest creating one array first using all input data you have and
the subsequent usage of the WHERE function, combined with a definition
of an appropriate colour bar using TVLCT. You can find a crude
elevation colour bar here (http://tinyurl.com/9682g), which uses index
0 as blue for the ocean, colurs 1 to 80 for shades of green and brown
and finally white. Using this your code could look like:
...
add the definiton of the colour bar here
...
...
You can similarily use the upper colours > 80 for your whatever else
you want to display
...
; Scale the topography between 0 and 3000 m,
; such that only the 80 colours of thr elevation colour bar are used:
plot_array = bytscl(topography, min = 0, max = 3000, top = 80)
; Mask ocean areas
idx = where(landsea eq 0, n)
; Setting the ocean pixels to 0 will make them appear blue.
if n gt 0 then plot_array[idx] = 0
; Now you want to ass "some other variable".
; I guess this variable does not fill the entire plot region,
; but is given e.g. in an array with the same dimension as the
; topography and the landsea mask. Let's assume it can also be
; identified by a threshhold, in this example the values between 1 and
100
; should be displayed using the colours 81 to 90 (which you have to add
to
; the colour bar in advancve)
idx = where(additional_data gt 0, n)
if n gt 0 then plot_array[idx] = $
bytscl(additional_data[idx], min = 1, max = 100 top = 9) + 81
; And finally:
tv, plot_array
Cheers,
Peter
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