DATA OPERATING DEVICE

摘要

Scale-changing method and 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 3 which operates on receipt of the image data from the scanner 2 to perform a scale-change operation on the pels, first in the image row direction and then in the image column direction. The row scale-change operation is performed by scale-change projector 5 which functions to replace sub-groups of pels in the input image rows by single pels at its output. The number of pels in the sub-groups are determined by the degree of compression required to convert to the lower pel resolution. The significance of the output bits replacing the sub-groups is determined in accordance with predetermined algorithms having regard to the significance of pels in a selected horizontal 'window' of pels which includes the sub-group of pels under consideration. The image data emerging from projector 5, consolidated in the row direction, is further processed by a second scale-change projector 6 which performs the column scale-changing operation. The projector 6 operates in a similar fashion to projector 5 except that in this case sub-groups of pels in the image column direction are replaced by single pels at its output. Again, the size of the sub-groups are determined by the degree of compression required to convert to the lower pel resolution. The significance of the output pels replacing the sub-groups is determined as in the previous step in accordance with predetermined algorithm having regard to the significance of pels in a selected vertical 'window' of pels which includes the sub-group of pels under consideration.