This app takes a different tack than most apps that add filters and effects to your photos. With Gridditor, the photo you use will be the focal point and you can choose four effects (out of 22 total) in each cardinal direction. The center of the grid is your original photo that doesn't have any effects, but out toward the edges of the grid, each effect intensifies, letting you blend effects at the corners or choose something closer to center for a less intense difference.
Even when you settle on a blend of effects, you can make the finished product your new focal point, select different filters, and swipe around the grid to see what your new set of filters produce.
Gridditor doesn't do everything. You won't be able to add frames or labels, and your sharing options are fairly limited. But if you want a way to preview what different effects look like in advance, the gridlike interface layout is a unique and effective option.