Abstract: An interactive display system includes a display terminal on which an operator may display the data contained in windows (14.1, 14.2 . . . ) on formatted application data (PS 1, PS 2 . . . ) in selected viewports (15.1, 15.2 . . . ) on the screen 13. The system is provided with storage (4), both real and virtual, into which a presentation interface service (2) loads dynamically the entire formatted data (PS 1, PS 2 . . . ) of each application (list 1, list 2 . . . ) as it is invoked by the user. A screen manager (7) maps the data contained in the defined windows into locations (16.1, 16.2 . . . ) of a programmable symbol refresh buffer (6, 8) determined by the corresponding position of viewports (15.1, 15.2 . . . ) on the screen defined by the user and through which the windows are to be viewed.

Abstract: Graphical data on a document is raster scanned and the resulting bit pattern is processed to provide a processed bit pattern which represents lines which each are a single pel in width and indicative of the shapes of objects scanned on the document. These single pel wide lines may represent the outlines of objects on the center lines. The processed bit pattern is then directed to a line follower in which bits representing contiguous pels are detected and tested for linearity. When contiguous pels fail the linearity test, a new vector is started and the vector being tracked is terminated. Hardware for performing these operations is described. The resulting vector list is stored until needed for display. Optionally a display station can be used to correct faulty vectors or to encode alphanumeric data in a more convenient format than vector coding.

Abstract: Data manipulation apparatus is described for converting raster-scanned data received, for example, from a scanner 2 at a first picture element (pel) resolution to a second lower pel resolution for display, for example, on a CRT terminal 4. The apparatus includes a scale-changing means 8 which functions to replace selected subgroups of pels in the input image by single pels at its output. The significance of each single pel reflects the presence or absence of a pel representing part of an image object in the associated subgroup of pels. The number of pels in the selected subgroups are determined by the degree of compression required to convert to the lower pel resolution. Prior to scale change, the apparatus functions to modify the input data in order to minimize merging of adjacent image objects as a result of scale change and thereby improve the legibility of the output image at the lower resolution.