Using Colormaps in my ImGui application

[JamAndCheese]

Hello, (I hope this is the right place to ask this. If not, please direct me to the right place or feel free to move it.)

I have an ImGui application that I wrote to display data bitmaps, single-channel normalized data (0.0 to 1.0), form various sources. I implemented my own colormaps (which included a Jet-like palette). However, seeing your amazing work on Colormaps, I would like to include ImPlot just to leverage this. Is this possible?

What I would need is a transformation of my 0.0 - 1.0 values into an RGB8 triplet or an equivalent ImU32, in which I will ignore the Alpha components. I assume that one of your available colormaps would have been selected previously. (I will probably make them all available for user selection)

Looking forward to any ideas or comments!

[epezent]

We have SampleColormap which returns an ImVec4 given t [0 1]. We could expose an ImU32 version if that's what you are asking for.

[JamAndCheese]

That would be awesome if you do. However I will start playing with SampleColormap and convert the floats for now. Thank you for taking the time to respond!

[JamAndCheese]

@epezent I found a bug in your SampleColormapU32 function. See the original return commented out. It was not using the argument cmap, therefore it was always using the current style one.

ImU32  SampleColormapU32(float t, ImPlotColormap cmap) {
    ImPlotContext& gp = *GImPlot;
    cmap = cmap == IMPLOT_AUTO ? gp.Style.Colormap : cmap;
    IM_ASSERT_USER_ERROR(cmap >= 0 && cmap < gp.ColormapData.Count, "Invalid colormap index!");
    //    return gp.ColormapData.LerpTable(gp.Style.Colormap,t);
    return gp.ColormapData.LerpTable( cmap, t );
}

[epezent]

Fixed. I suppose you discovered you can include implot_internal.h and use the ImU32 version now. My point above was in regards to exposing this in the "official" API (i.e. implot.h).

[JamAndCheese]

Thank you!