Universal colormap applicabillity

[jleibs]

We have a nice configurable colormap component but at present you can only use it for DeltphImage and Tensors.

Any archetype that uses Color should be able to work with a scalar value and a colormap.

[Wumpf]

another motivation is size (see #6976):

When logging a lot of images, the data in rerun grows quickly. A lot of images are RGB heatmaps that stem from grayscale images. It would be nice being able to log images as grayscale and visualize them in rerun with a given heatmap.

[grtlr]

This would be very cool in combination with the graph viewer as well, for example to create bubble charts or color groups of nodes that belong together in a graph.

I really like the modular API of d3-scale together with d3-scale-chromatic for all kinds of scales. When we implement this we can take a look at their topology, and support many of their scales, ideally configurable via blueprints.

• Categorical: https://d3js.org/d3-scale-chromatic/categorical
• Cyclical: https://d3js.org/d3-scale-chromatic/cyclical
• Diverging: https://d3js.org/d3-scale-chromatic/diverging
• Sequential: https://d3js.org/d3-scale-chromatic/sequential

For many use cases, it also makes sense to have control over the domain and the range of the scale. I'd be happy to work on this!

[pablovela5620]

Wanted to chime in here, I'd love to use colormap for a "confidence map", ideally I would love to log as a monochrome image like https://github.com/rerun-io/rerun/issues/6976 . I'm getting around it by using a DepthImage instead that supports colormap but this leads to issues if logging in both 2d+3d views (I can deal with this by excluding the depth map from the 3d view using a blueprint but its a bit of a pain). Setting a color map on a monochrome image would be ideal! Another option is for me to do it manually with opecv or matplotlib and just log that image. I'll look into using a tensor instead as well since I think this would probably not have the 3d spatial view issues