| 摘要 |
<p>A method and apparatus for rescreening a halftone image to produce an edge-enhanced halftone copy from a halftone original. The halftone original is scanned by a raster input scanner and the resultant analog voltage thresholded to produce a one bit per pixel bit stream. A six bit per pixel gray scale output is produced therefrom by adding an integrated value and an edge ehancement value for each input pixel received. The integrated value is calculated by summing the number of one bits in the seven by nine bit section surrounding each pixel. The edge enhancement value is calculated by determining the difference between the number of one bits in the right and left halves, and upper and lower halves, of the six by seven bit section surrounding each pixel. A set of equations is used to process these differences to produce an edge enhancement value which is added to the integrated value. From this six bit per pixel gray scale output the six bit output can be preserved, or a halftone copy can be produced by any well-known process. A simple and inexpensive circuit to perform the above functions at high data rates is also disclosed. </p> |
