The data used by a computer to represent and display a picture conventionally requires very large amounts of dedicated storage. As the trend continues towards high resolution graphics employing a wide range of colours the associated volume of data often expands to a point where sophisticated techniques become essential to maintain a practical interactive system. Considerable research has been conducted into coding schemes which compress the volume of picture data. These methods are clearly of great value in reducing the delay which results from transmitting picture data between sites. Codes which also serve directly as a source for real-time display are better still. The quadtree method of picture encoding, which has previously been successfully employed in the field of picture processing, is shown in this thesis to provide the basis for an integrated approach to data compression in the field of computer graphics. The display of colour pictures from quadtree code is performed by customised hardware which operates in conjunction with a general purpose processor. A prototype system is described which provides efficient downloading of pictures from a host and rapid display of locally stored pictures. The amenability of quadtree code to manipulation is demonstrated by incorporating a limited capability to pan and zoom on a picture. Application of the method to picture archive retrieval is examined.
|Date of Award||1984|