Abstract: An Internet-based printing system allows for the distribution and printing of documents and images in a secure, controlled manner. The system includes a secure printer that receives, decrypts and prints documents supplied by a document server. Security of the system is realized by an aggregate of a secure communication protocol, smart card technology and the computational infeasibility of breaking a public key cryptographic system. The system may be used for electronic commerce, in which copies are made on a “pay-per-print” basis.

Abstract: A process and apparatus is described to improve error diffusion halftone imaging by reducing the amount of time necessary to perform the halftoning process. This processing time reduction is produced without sacrificing the quality of the output binary images by achieving parallelism of error diffusion within an image row. The method works by cutting each image row into a number of segments and error diffusing these segments in parallel. It utilizes two different error diffusion filters: the cut filter for the pixel just before the cuts and the normal filter for the rest of the pixels. Dependencies among the segments is eliminated by ensuring that the cut filter has zero weight for the right neighboring pixel. The normal filter can be any filters that can show excellent quality of the output binary images. Banding artifacts along the cuts are minimized through careful design of the cut filter.

Abstract: An improved multi-dot halftoning method to print a non-text halftone image from a non-text gray-scale image by comparing the gray-scale image to a transformed dither matrix to generate and to print the halftone image. The transformed dither matrix is tuned to reduce undesirable artifacts in the printed image. In one set of process steps to generate the transformed dither matrix, an original dither matrix with a number of original levels is picked. A selected number of the original matrix is tiled to build the large dither matrix. The large dither matrix is then transformed by operating on every original level in the large dither matrix. Each original level is split to create a group of finer levels that are in sequence and are all different from each other. A processor then replaces that original level in each of the tiled matrices by one of the finer levels such that the sequence of finer levels follows a pattern in the large dither matrix.