First draft of interpolation for heatmaps

Project.toml

@@ -7,6 +7,7 @@ version = "1.40.16"
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
 Contour = "d38c429a-6771-53c6-b99e-75d170b6e991"
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
+Dierckx = "39dd38d3-220a-591b-8e3c-4c3a8c710a94"
 Downloads = "f43a241f-c20a-4ad4-852c-f6b1247861c6"
 FFMPEG = "c87230d0-a227-11e9-1b43-d7ebe4e7570a"
 FixedPointNumbers = "53c48c17-4a7d-5ca2-90c5-79b7896eea93"
@@ -58,6 +59,7 @@ UnitfulExt = "Unitful"
 [compat]
 Aqua = "0.8"
 Contour = "0.5 - 0.6"
+Dierckx = "0.5.4"
 Downloads = "1"
 FFMPEG = "0.4.1"
 FixedPointNumbers = "0.6 - 0.8"

src/pipeline.jl

@@ -1,5 +1,5 @@
 # RecipesPipeline API
-
+using Dierckx
 ## Warnings
 
 function RecipesPipeline.warn_on_recipe_aliases!(
@@ -374,11 +374,35 @@ function RecipesPipeline.add_series!(plt::Plot, plotattributes)
         plotattributes[letter1], plotattributes[letter2] =
             plotattributes[letter2], plotattributes[letter1]
     end
+    if plotattributes[:seriestype] === :heatmap
+        if haskey(plotattributes, :interpolate)
+            s = plotattributes[:interpolate]
+            x = collect(plotattributes[:x])
+            y = collect(plotattributes[:y])
+            z = reshape(collect(plotattributes[:z]),4,4)
+            finerx, finery, zinterp = cubic_interp_2d( x, y, z, s )
+            plotattributes[:x] = finerx
+            plotattributes[:y] = finery
+            plotattributes[:z] = Surface(zinterp)
+            plotattributes[:size] = (length(finerx), length(finery))
+        end
+    end
     _expand_subplot_extrema(sp, plotattributes, plotattributes[:seriestype])
     _update_series_attributes!(plotattributes, plt, sp)
     return _add_the_series(plt, sp, plotattributes)
 end
 
+function cubic_interp_2d( x, y, data, s )
+    spl = Spline2D(y, x, data; kx=3, ky=3, s=0.0)
+    finerx = LinRange(x[1], x[end], s[1])
+    finery = LinRange(y[1], y[end], s[2])
+    data_interp = Array{Float64}(undef, s[2], s[1])
+    for (i,yint) ∈ enumerate(finery), (j,xint) ∈ enumerate(finerx)
+        data_interp[i,j] = evaluate(spl, yint, xint)
+    end
+    return finerx, finery, data_interp
+end
+
 # getting ready to add the series... last update to subplot from anything
 # that might have been added during series recipes
 function _prepare_subplot(plt::Plot{T}, plotattributes::AKW) where {T}

test/test_misc.jl

@@ -351,4 +351,13 @@ Plots.with(:gr) do
         show(devnull, scatter(x, y))
         # show(devnull, plot(x, y))  # currently unsupported
     end
+
+    @testset "heatmap interpolation" begin
+        @test heatmap(
+            1:4,
+            1:4,
+            [1 2 3 4; 5 6 7 8; 9 10 11 12; 13 14 15 16];
+            interpolate = (10, 10),
+        )
+    end
 end