From 6a1af1c888a15793e06205f0da84abf3723577c8 Mon Sep 17 00:00:00 2001
From: Daniel Schwabeneder <daschw@disroot.org>
Date: Sun, 4 Oct 2020 15:02:38 +0200
Subject: [PATCH] add explanation

---
 src/backends/gr.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backends/gr.jl b/src/backends/gr.jl
index dace2338..0b20c460 100644
--- a/src/backends/gr.jl
+++ b/src/backends/gr.jl
@@ -1537,6 +1537,7 @@ function gr_add_series(sp, series)
         dmin, dmax = GR.gr3.volume(y.v, 0)
     elseif st in (:heatmap, :image)
         if !ispolar(series)
+            # `z` is already transposed, so we need to reverse before passing its size.
             x, y = heatmap_edges(x, xscale, y, yscale, reverse(size(z)))
         end
         if st === :heatmap