DATA MANIPULATION APPARATUS FOR CONVERTING RASTER-SCANNED DATA TO A LOWER RESOLUTION

摘要

Data manipulation apparatus is described for converting raster-scanned data received for example from a scanner at a first picture element (pel) resolution to a second lower pel resolution for display for example on a CRT terminal. The apparatus includes a scale-changing means which functions to replace selected sub-groups 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 sub groups 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. The scanned data is first supplied to a data sensitive thinner which detects narrow gaps between adjacent objects and selectively detects image object edge pels in order to widen the gap. The selectively thinned scanned data is then supplied to a further thinner which removes excess image pels from selected edges of the image objects. The data from the further thinner is then supplied to a data sensitive merge inhibit unit which moves selected image object pels from a sub-group in which merging as a result of scale change will occur to an adjacent sub-group where merging will not occur. Removal of a pel by the selective thinner, or by the further thinner or movement of a pel by the inhibit unit is inhibited if to do so would result in fragmentation of the associated image object. UK9-78-019