fix image sampling

src/function.jl

@@ -347,7 +347,7 @@ function _sample(f::FeFunction)
 	I1 = round.(Int, SVector(maximum(A[1, :]), maximum(A[2, :])) .- m0) .+ 1
 
 	for I in CartesianIndex(I0[1], I0[2]):CartesianIndex(I1[1], I1[2])
-            x = SVector(Tuple(I) .- m0)
+            x = SVector(Tuple(I) .- 1 .+ m0)
             # TODO: move to global-to-local function or inside-triangle test
             xloc = (A[:, SUnitRange(2, 3)] .- A[:, 1])::SArray \
                 (x .- A[:, 1])