Re-thinking our color maps

Sunday: Tutorial on color theory, by Theresa-Marie Rhyne. Almost too basic, but interesting to get insight on how to build good color maps for visualization. The tutorial lead me to think we should pay more attention to this aspect.

First of all, I discovered the existence of a whole bunch of software tool to help build color tables:

• Adobe Kuler
• ColorBrewer
• Color Scheme designer

These tools can build color tables automatically from any picture. They also allow users to create new tables from scratch. Some have functionality to constrain user in choosing colors that follow certain basic rules of color theory. Another interesting tool is Vischeck. It takes any image as input and generates a version of that image as seen by each type of color-blind people.

Now, a couple of insights on how to mix colors.

Generally, colors that are more or less spread around a curve passing through the center of the color wheel (see picture) work well. Colors that are directly opposite in the wheel should not be used together. There should be at least a slight curvature in line passing through the color points.

Color works as an attention attractor. But the amount of a color in an image matters a lot. A small patch of red doesn't have the same effect as a large area covered with red. Bright colors should be used with moderation.


A good source of inspiration for interesting color mixes is the Color Field Painting movement.

Morris Louis, Where, an example painting
from the Color Field movement

A couple of references on color theory and art of color mixing:

• Real-world color management by Bruce Fraser and Chris Murphy
• The interaction of colors by Josef Albers
• A field guide to digital color by Maureen Stone 

Simple DTI tracts navigation

Very simple 2D interface to navigate DTI fiber tract (paper here). The method is simple. First, the tract data is analysed to cluster similar tracts together and form "bundles".

Those bundles can be represented by an average line segment that is projected in 2D. The 2D view is rendered using the Google maps API. It is then possible to select bundles from the uncluttered 2D views. All tracts that belong to the selected bundles are then highlighted in a traditional 3D rendering of all tracts (upper left corner).