A Novel Approach to Real-time Bilinear Interpolation

Bilinear interpolation is often used to improve image quality after performing spatial transformation operations such as digital zooming or rotation. In the traditional case where the input coordinates appear in a raster-based fashion, the required pixel values can be obtained from the previous calculation, the frame buffer and a single line cache. This paper presents a novel approach to performing real-time bilinear interpolation that is useful in applications such as lens distortion correction where the input coordinates follow a curved path that spans multiple rows. To help retrieve the required pixels in a single clock cycle under imposed data bandwidth constraints a unique caching system has been devised. In the event that constraints make it impossible to obtain the four required pixel values, the approach performs a modified three-point interpolation. An example field programmable gate array implementation of the bilinear interpolation method used in conjunction with a lens distortion correction algorithm has been successfully completed.