Speed up heatmap for large (2500x2500) matrices?

New to Julia
4

looks like using GR directly is much faster:

julia> using GR

julia> a = rand(2500,2500);

julia> @time display(heatmap(a))
nothing
  3.725224 seconds (39.82 M allocations: 1.523 GiB, 8.06% gc time)

julia> @time display(heatmap(a))
nothing
  1.102791 seconds (31.25 M allocations: 1.094 GiB, 6.55% gc time)