[GRASS-dev] G_exp_colors()?

[Hamish]

> Hamish wrote:
> > I am working with MODIS Aqua imagery in HDF4 format. (level 3)
...
> > I added a mini-tutorial here:
> >   http://grass.gdf-hannover.de/wiki/MODIS
...
> > The Chlorophyll-a concentration data comes in log form, 0-65535.
...
> > The metadata (available through gdalinfo) gives the formula and test
> > points to convert to mg/m^3:
> >   r.mapcalc "${map}.chlor_a = 10^(($Slope * $map) + $Intercept)"
> 
> > ie a histogram of that starts high and exponentially drops to 0. By
> > 2.0 there are few data cells left, but real data continues up to the
> > max in areas having plankton blooms.
...
> > So how to make nice color rules for that? 'r.colors -g' does the
> > opposite of what I want,

Glynn.
> Odd. Theoretically, it should do exactly what you want.

You are right, -g is the right thing to use, it's just that the data is
/so/ logarithmic that it only brings out a little more detail and it
appears like nothing happened. (it became clear after displaying a
legend, changing the color rules, then redrawing)


Hamish



     
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