Respect scale and nonlinear values in PlotUtils cgrads

NEWS.md

@@ -4,6 +4,7 @@
 
 - Switched to `MathTeXEngine v0.4`, which improves the look of LaTeXStrings [#1952](https://github.com/JuliaPlots/Makie.jl/pull/1952).
 - Added subtitle capability to `Axis` [#1859](https://github.com/JuliaPlots/Makie.jl/pull/1859).
+- Fixed a bug where scaled colormaps constructed using `Makie.cgrad` were not interpreted correctly.
 
 ## v0.17.2
 

ReferenceTests/src/tests/examples2d.jl

@@ -467,6 +467,37 @@ end
     f
 end
 
+@reference_test "nonlinear colormap" begin
+    n = 100
+    categorical = [false, true]
+    scales = [exp, identity, log, log10]
+    fig = Figure(resolution = (500, 250))
+    ax = Axis(fig[1, 1])
+    for (i, cat) in enumerate(categorical)
+        for (j, scale) in enumerate(scales)
+            cg = if cat
+                cgrad(:viridis, 5; scale = scale, categorical=true)
+            else
+                cgrad(:viridis; scale = scale, categorical=nothing)
+            end
+            lines!(ax, Point2f.(LinRange(i+0.1, i+0.9, n), j); color = 1:n, colormap = cg, linewidth = 10)
+        end
+    end
+    ax.xticks[] = ((1:length(categorical)) .+ 0.5, ["categorical=false", "categorical=true"])
+    ax.yticks[] = ((1:length(scales)), string.(scales))
+    fig
+end
+
+@reference_test "colormap with specific values" begin
+    cmap = cgrad([:black,:white,:orange],[0,0.2,1])
+    fig = Figure(resolution=(400,200))
+    ax = Axis(fig[1,1])
+    x = range(0,1,length=50)
+    scatter!(fig[1,1],Point2.(x,fill(0.,50)),color=x,colormap=cmap)
+    hidedecorations!(ax)
+    Colorbar(fig[2,1],vertical=false,colormap=cmap)
+    fig
+end
 
 @reference_test "multi rect with poly" begin
     # use thick strokewidth, so it will make tests fail if something is missing

src/conversions.jl

@@ -1086,7 +1086,7 @@ function to_colormap(cs::Union{String, Symbol})::Vector{RGBAf}
             return to_colormap(ColorBrewer.palette(cs_string, 8))
         else
             # cs_string must be in plotutils_names
-            return to_colormap(PlotUtils.get_colorscheme(Symbol(cs_string)).colors)
+            return to_colormap(PlotUtils.get_colorscheme(Symbol(cs_string)))
         end
     else
         error(
@@ -1099,11 +1099,12 @@ function to_colormap(cs::Union{String, Symbol})::Vector{RGBAf}
     end
 end
 
-to_colormap(cg::PlotUtils.ContinuousColorGradient)::Vector{RGBAf} = to_colormap(cg.colors)
-
-function to_colormap(cg::PlotUtils.CategoricalColorGradient)::Vector{RGBAf}
-    colors = to_colormap(cg.colors)
-    return repeat(colors; inner=20)
+# Handle inbuilt PlotUtils types
+function to_colormap(cg::PlotUtils.ColorGradient)::Vector{RGBAf}
+    # We sample the colormap using cg[val]. This way, we get a concrete representation of
+    # the underlying gradient, like it being categorical or using a log scale.
+    # 256 is just a high enough constant, without being too big to slow things down.
+    return to_colormap(getindex.(Ref(cg), LinRange(first(cg.values), last(cg.values), 256)))
 end
 
 """

src/makielayout/blocks/colorbar.jl

@@ -4,7 +4,7 @@ function block_docs(::Type{Colorbar})
     chosen according to the colorrange.
 
     You can set colorrange and colormap manually, or pass a plot object as the second argument
-    to copy its respective attributes. 
+    to copy its respective attributes.
 
     ## Constructors
 
@@ -181,20 +181,17 @@ function initialize_block!(cb::Colorbar)
         end
 
         colors = get.(Ref(gradient), (steps[1:end-1] .+ steps[2:end]) ./2)
-
         rects, colors
     end
 
     colors = lift(x -> getindex(x, 2), rects_and_colors)
-
     rects = poly!(blockscene,
         lift(x -> getindex(x, 1), rects_and_colors),
         color = colors,
         visible = map_is_categorical,
         inspectable = false
     )
 
-
     # for continous colormaps we sample a 1d image
     # to avoid white lines when rendering vector graphics