Image processing method for execution externally and internally to a printer
View Patent ↗A method for image processing data representing a page to be printed includes the step of respectively receiving, in a data processing apparatus, external to a printer, data representing a bi-level black layer and a contone layer of a page to be printed. In the data processing apparatus, a halftoning process is applied to data representing the contone layer to form a bi-level cyan, yellow, magenta, and black (CYMK) layer. In the data processing apparatus, a compositing process is applied to data representing the bi-level black layer to composite the bi-level black layer over the bi-level CYMK layer to form a bi-level CYMK image of the page to be printed. The data representing the halftoned and composited layers is compressed to generate compressed image data. The compressed image data is written to the printer. An expansion process is applied to the compressed image data in the printer to generate data representing the page to be printed. The page is printed with the printer.
1. A method for image processing data representing a page to be printed, the method comprising the steps of:
respectively receiving, in a data processing apparatus, external to a printer, data representing a bi-level black layer and a contone layer of a page to be printed;
applying, in the data processing apparatus, a halftoning process to data representing the contone layer to form a bi-level cyan, yellow, magenta, and black (CYMK) layer;
applying, in the data processing apparatus, a compositing process to data representing the bi-level black layer to composite the bi-level black layer over the bi-level CYMK layer to form a bi-level CYMK image of the page to be printed;
compressing the data representing the halftoned and composited layers to generate compressed image data;
writing the compressed image data to the printer;
applying, in the printer, an expansion process to the compressed image data to generate data representing the page to be printed; and
printing the page with the printer.
2. A method as claimed in claim 1 , in which the step of compressing the data representing the halftoned layer includes the step of applying a JPEG compression algorithm to the halftoned layer data.
3. A method as claimed in claim 2 , in which the step of compressing the halftoned layer data is carried out to generate an interleaved color JPEG bytestream.
4. A method as claimed in claim 1 , in which the step of compressing the data representing the bi-level black layer includes the step of applying one of a Group 3 and a Group 4 fax algorithm to the bi-level black layer data.
5. A method as claimed in claim 1 , in which the step of compressing the data representing the bi-level black layer includes the step of applying a Bi-Level Edge Delta and Runlength (EDRL) Compression Format to the bi-level black layer data.
6. A method as claimed in claim 1 , in which the step of applying the expansion process includes the step of buffering the compressed data to be printed.
7. A method as claimed in claim 6 , in which the step of applying the expansion process includes the steps of decompressing the contone CMYK image data, halftoning resulting contone pixels to bi-level CMYK dots, decompressing bi-level black text data, and compositing resulting bi-level black text dots over corresponding bi-level CMYK image dots.