support scale in get_...color

src/utils.jl

@@ -463,28 +463,34 @@ for comp in (:line, :fill, :marker)
 
     @eval begin
         # defines `get_linecolor`, `get_fillcolor` and `get_markercolor` <- for grep
-        function $get_compcolor(series, cmin::Real, cmax::Real, i::Int = 1)
+        function $get_compcolor(series, cmin::Real, cmax::Real, i::Integer = 1, s::Symbol = :identity)
             c = series[$Symbol($compcolor)]  # series[:linecolor], series[:fillcolor], series[:markercolor]
             z = series[$Symbol($comp_z)]  # series[:line_z], series[:fill_z], series[:marker_z]
             if z === nothing
                 isa(c, ColorGradient) ? c : plot_color(_cycle(c, i))
             else
-                get(get_gradient(c), z[i], (cmin, cmax))
+                grad = get_gradient(c)
+                if s === :identity
+                    get(grad, z[i], (cmin, cmax))
+                else
+                    base = _logScaleBases[s]
+                    get(grad, log(base, z[i]), (log(base, cmin), log(base, cmax)))
+                end
             end
         end
 
-        $get_compcolor(series, clims::Tuple{<:Number,<:Number}, i::Int = 1) =
-            $get_compcolor(series, clims[1], clims[2], i)
-
-        function $get_compcolor(series, i::Int = 1)
+        function $get_compcolor(series, i::Integer = 1, s::Symbol = :identity)
             if series[$Symbol($comp_z)] === nothing
-                $get_compcolor(series, 0, 1, i)
+                $get_compcolor(series, 0, 1, i, s)
             else
-                $get_compcolor(series, get_clims(series[:subplot]), i)
+                $get_compcolor(series, get_clims(series[:subplot]), i, s)
             end
         end
 
-        $get_compalpha(series, i::Int = 1) = _cycle(series[$Symbol($compalpha)], i)
+        $get_compcolor(series, clims::NTuple{2,<:Number}, args...) =
+            $get_compcolor(series, clims[1], clims[2], args...)
+
+        $get_compalpha(series, i::Integer = 1) = _cycle(series[$Symbol($compalpha)], i)
     end
 end