1. Field of Invention
This invention is directed to a finite response filter (FIR) method and apparatus.
2. Related Art
FIR filters are used in many fields such as document reproduction or printing of documents, for example. Almost all printed matter uses halftone screens. These halftone screens are traditionally optimized for the printing device, and may cause considerable halftone interference, such as visible large-area beating and visible Moire patterns, if not properly removed from the original scanned image. Image data generated by scanning printed matter is often filtered to remove unwanted artifacts, such as halftone screens. The suppression of halftones is especially important for color documents, since these are typically printed with four or more color separations containing slightly different screens at different angles and or frequencies, and these may interact with each other to cause undesirable spatial artifacts.