How can I generate a range of pantones for a map?

Question

When I am given a map (or make one...) I often like to get an idea of the range of colours present. One thing this does is it allows me to quickly visualize contrast (helps build maps for colour blind readers).

I was wondering what some options are to automatically or easily generate a range of pantones for any given map? There may be a different process when dealing with vector based maps, like a PDF , PS/EPS, or a SVG.

I wonder if there is a tool or plugin for GIMP that will scan an image, get the rgb/cmyk value for every pixel and summarize with a count showing the occurrence...

An opensource suggestion would be ideal. I use GIMP a fair bit, but only for literal design/layout and have not delved into image analysis.

I have ArcGIS 10 but without spatial analyst so I have no raster tools available in that package.

Sorry if this is on the wrong SE site, maybe better for photo.SE?

Answer 1

QGIS can generate histograms and basic statistics about the image.
GRASS gis can also generate statistics (r.report) and manipulate each band or compositions with a wide range of function (http://grass.fbk.eu/grass64/manuals/html64_user/raster.html).

They both open source but Qgis is a little bit easyer to get started, just open a new project and add a raster layer, then double click on it, you will see the "Metadata" tab and the "histogram" tab.