<title>Fast edge-preserving image interpolation algorithm with an arbitrary aspect ratio</title>

Abstract

Conventional interpolation techniques, including pixel replication, bilinear interpolation and spline based methods have been popularly used in commercial applications. It is often desired that the interpolation process is able to accurately and fastly increase the spatial resolution of an image at an arbitrary aspect ratio and with sharp edges. These do not generally happen to conventional algorithms, which will consume a great effort to interpolate an image at an arbitrary ratio and tend to blur edges or introduce blocking artifacts. In this correspondence, we propose an interpolation system that is more general than the existing ones. The method is based on the fact that the Hartley transform (HT) at an arbitrary frequency can be expressed as a weighted sum of its Discrete Hartley transform (DHT) coefficients. These weights can be suitably approximated so that the HT is very nearly the sum of (1) a few dominant terms of the sum of the DHT coefficients, and (2) the DHT of a new sequence obtained by multiplying the original sequence with a saw-tooth function. If we take the inverse discrete Hartley transform (IDHT) of an image; then by using the algorithm described above, the spatial sample at an arbitrary location can be fastly computed by the fast Hartley transform (FHT) algorithm. In addition to retaining the computational efficiency of the FHT algorithm, experimental results have revealed that the proposed system preserves the sharp edge of the original image.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.