I have a raster layer with a band with values from -137 to 9229. I want to create a color scheme showing how far from 0 the positive numbers are in one color, and how far from zero the negative numbers are in another color, with a neutral 0 (that, unmistakenly, doesn't lean towards the positive or negative colors, nor diverges from the color scale).
Moreover I'd like a "-55"-area to be just as far from the neutral color (0) as a "+55"-area, but in different colors. So if neutral would be #333, then -5 might be #338, and +5 would be #833, even though the array of values, as in this case, is heavily biased towards positive numbers.
Hope that explains my problem. I'd greatly appreciate any help I get! This is for my Bachelor thesis project on the creation of the metro and highway system in DC during the 50s to 80s.
EDIT: Oh, gosh. I forgot to tell you I'm using QGIS 1.7.4 on an OSX Lion. And have very limited access to Cartographica and ArcGIS full suite.
Best regards, Henrik