Add fast path for indices on non-invertible TransformedGrid

src/indices.jl

@@ -74,6 +74,14 @@ function indices(grid::OrthoRectilinearGrid, box::Box)
   LinearIndices(size(grid))[range] |> vec
 end
 
+function indices(grid::TransformedGrid, geometry::Geometry)
+  # construct reverse transform from revertible steps
+  revtrans = reduce(→, reverse(filter(isrevertible, transform(t))))
+
+  # find indices in non-transformed space
+  indices(parent(grid), revtrans(geometry))
+end
+
 # ----------------
 # CARTESIAN RANGE
 # ----------------

test/indices.jl

@@ -202,4 +202,18 @@
   @test linds[2, 2] == only(indices(grid, p4))
   @test linds[10, 10] == only(indices(grid, p5))
   @test isempty(indices(grid, p6))
+
+  # transformed grid
+  g = cartgrid(20, 20)
+  poly1 = PolyArea(cart.([(3, 3), (9, 9), (3, 15), (17, 15), (17, 3)]))
+  expectedinds = indices(g, poly1)
+  linds = LinearIndices(size(g))
+  @test linds[12, 6] ∈ expectedinds
+  taff = Rotate(Angle2d(T(π / 2)))
+  tmorph = Morphological(c -> Cartesian(c.x + c.y, c.y, c.x - c.y))
+  tseq = taff → tmorph
+  grid = TransformedGrid(g, tseq)
+  poly2 = taff(poly1)
+  actualinds = indices(grid, poly2)
+  @test actualinds == expectedinds
 end