Stacked Integral Image

Filtering in digital images via Integral Image yields fast computation times for uniform filtering. The extension by Heckbert to perform filtering via repeated integration provides a way for non-uniform filtering, but has its own limitations. A recent method by Hussein et al. provides non-uniform filtering by Euler expansion of filtering kernels, and is called kernel integral method. We propose a simplification for non-uniform filtering by stacking of box filters from a single integral image. Results show speedups of as much as 40:1, similar to run time performance gains in kernel integral method, when comparing to naïve nonuniform filtering, while at the same time reducing the setup time drastically.