Add post on custom array indices

blog/_posts/offsetarrays_figures/figures.jl

@@ -0,0 +1,35 @@
+using TestImages, Images, OffsetArrays, CoordinateTransformations, Rotations
+
+# This is an alternative means of accomplishing the same rotation as
+# described in the blog post, here by translating the starting image
+# directly so that 0,0 is the center of the rotation.
+img = OffsetArray(testimage("cameraman"), (-125, -250))
+tfm = LinearMap(RotMatrix(-pi/6))
+img_rotated = warp(img, tfm)
+save("cameraman.png", img)
+save("cameraman_rotated.png", clamp01nan.(img_rotated))
+cv = colorview(RGB, paddedviews(0, img, img_rotated, img)...)
+save("cameraman_overlay.png", clamp01nan.(cv))
+pimg = parent(img)
+tfmcntr = recenter(RotMatrix(-pi/6), center(pimg))
+img_rotated_cntr = warp(pimg, tfmcntr)
+cvc = colorview(RGB, paddedviews(0, pimg, img_rotated_cntr, pimg)...)
+save("cameraman_overlay_center.png", clamp01nan.(cvc))
+inds = map(intersect, indices(img), indices(img_rotated))
+cvi = colorview(RGB, img[inds...], img_rotated[inds...], img[inds...])
+save("cameraman_overlay_interior.png", clamp01nan.(cvi))
+
+using Plots
+pyplot()
+ps = []
+isfirst = true
+for (i, kern) in enumerate((centered([1]), OffsetArray([1], 2:2), OffsetArray([1], -5:-5)))
+    a = 1:8
+    af = imfilter(a, kern, Fill(0))
+    p = plot(a, color="black", xlims=(-3,9), ylims=(0,8), grid=false, linewidth=2, label=isfirst?"input":"", xticks=i == 3 ? (-3:3:9) : nothing)
+    plot!(p, -indices(kern, 1), 0:1, color="blue", linewidth=2, label=isfirst?"kernel":"")
+    plot!(p, af, color="red", label=isfirst?"output":"")
+    push!(ps, p)
+    isfirst = false
+end
+savefig(plot(ps..., layout=(3,1)), "filtering.eps")