Novel Hardware Algorithms for Row-Parallel Integral Image Calculation

The integral image is an intermediate image representation that allows rapid calculation of rectangular features at constant speed, irrespective of filter size, and is particularly useful for multi-scale computer vision algorithms like Speeded-Up Robust Features (SURF). Although calculation of the integral image involves simple addition operations, the total number of operations is significant due to the generally large size of image data. Recursive equations allow considerable reduction in the required number of addition operations but require calculation of the integral image in a serial fashion. This is generally not desirable for real-time embedded vision systems with strict time limitations and low-powered but parallel hardware resources. With the objective of minimizing the hardware resources involved, this paper proposes two novel hardware algorithms based on decomposition of these recursive equations, allowing calculation of up to four integral image values in a row-parallel way with out significantly increasing the number of addition operations.