Printing systems, including inkjet and laser printers, are well known in the art. In inkjet printing systems, an inkjet printhead is typically mounted on a carriage that is moved back and forth across a print media, such as paper. As the printhead is moved across the print media, a control system activates the printhead to deposit or eject ink droplets onto the print media to form text and images. Ink is provided to the printhead from a supply of ink that is either carried by the carriage or mounted to a fixed receiving station.
In electrophotographic or “laser” printing systems, marking material commonly called “toner” is provided by an electrophotographic engine frequently referred to as a toner cartridge. The toner cartridge often includes an intermediate imaging device such as a drum, and a reservoir of imaging material such as powdered toner. The drum is charged using an energy source such as a scanning laser. The imaging material is attracted to the charged drum and is then transferred to print media.
Regardless of the printing technology, it has become common for printing systems to incorporate additional functionality, generally by the inclusion of a scanner. These multifunction or “All-in-One” systems allow a user to print, scan, copy, and fax documents. The desired function may typically be selected from a control panel on the printing system, or through a software menu structure. Typical control panels may comprise hard-wired buttons or controls, or may comprise liquid crystal displays (LCDs) that may or may not be touch-sensitive (in which case they may be referred to as touchscreens). Such displays normally provide graphical representations of various selectable features, for instance buttons, that the user may select by either touching the display with one's finger or scrolling through the features using an actual control panel button.
One common function provided by All-in-One printing systems is facsimile transmission, or “fax”. Fax is a relatively old technology in which the image on a sheet of paper is scanned and converted into audio tones that may be transmitted over common telephone lines. The low bandwidth of phone lines means that faxes are typically low resolution monochrome images.
Facsimile transmission works reasonably well when the original document consists of dark lines or text on a substantially white background. Facsimile transmission works much less well when the original document has characteristics that don't reproduce well as a low resolution monochrome image. When the original document is printed on colored paper, for example, artifacts in the background of the faxed image can seriously degrade the readability of the faxed document.
There is therefore a need for methods that allow for improved facsimile transmission of documents printed on color media.