Extract colours from a Palette

ROOT
1

I’d like to make a scatter plot, where each point has a different colour determined by a certain number, where that number represents some kind of an occupancy. I’d like to go from blue->green->yellow->red, as occupancy for that spot/data point is increasing. Now, I can do that with a few “if o<1, SetMarkerColor(kBlue)” or something, but then I’d end up having a lot of else if conditions until I get to red, and I’d like to have as many colours as I can.

Is there a way to extract the colours from the Rainbow palette, in which case having the colours would make it easier to make a linear scale with many "else if o<x, SetMarkerColor(…), lines, or is there a way to call the SetMarkerColor function with the colours of the rainbow palette, and somehow connect it to my occupancy based on which I’m colouring the points?

Thanks

2

Hi,

our graphics expert is away, but hopefully this will help you out.
You can loop through all the colours in the palette and assign a colour to your primitives like this:

auto cols = TColor::GetPalette();
// I suppose you have a vector of entities you want to draw here
for (int i=0;i<cols.GetSize() || i >= myObjects.size() ;i++) {
  myObjects[i].SetMarkerColor(cols.At(i));
}

Cheers,
D

3

Thanks :slight_smile:
In the end what I did was just extracting the RGB components of a colourmap from MATLAB and made a nx3 array in root, and then using a “for” loop, I added indices to each row of colours, and then I called SetMarkerColor(my_index).

4

Glad you could solve this!