| 摘要 |
An interactive raster-scanned display device has a microprocessor (1) and random access memory (3) which operate to issue instructions to a drawing engine (7) to cause it to load and erase image pel representation in an image buffer (9) in order to control display of images on, or removal of images from a display screen (8) in a conventional manner. A cursor control device (10) enables a user to interact by means of a cursor symbol with images on the screen. In order to reduce the demands imposed on the drawing engine during transformation of images over the screen, the system is configured so that, if during a transformation operation there is insufficient time for the engine to draw the entire image, it draws as much of the image as it is able in the time available. In the implementation, vectors representing the full image are held in a display list ordered by the user so that the most important visual elements of the image are specified, and hence drawn, first. Thus for example the order of the vectors may be such that those forming a simple skeletal or outline drawing are drawn first with, if time permits between move commands, the details added later. Clearly at the end of an operation the engine will go on drawing until the entire image is generated. |
