Multidimensional Signal and Color Image Processing Using Lattices

11Changing the Sampling Structure of an Image

11.1 Introduction

There are two main applications for changing the sampling structure of an image: resizing and format conversion (or standards conversion). Resizing generally involves displaying the image on the same display but with a larger or smaller size, and so with a different number of samples per picture height. Format conversion involves switching between different formats such as European and North American television standards, which may be displayed at the same size, but again with a different number of samples per picture height and perhaps with different temporal sampling characteristics. This application is one where the picture height is a particularly convenient choice for the unit of length.

An image is initially sampled on a lattice , and it is required to produce a new image sampled on a different lattice . If is less dense than , we are downsampling; conversely if is denser than , we are upsampling. The problem we ...