Patch codes with improved robustness

A method for encoding information on a printed page comprising:

• receiving a data structure associating color values of a set of printed color patches with datum values, each of the color patches in the set representing a unique code value, whereby ones of the patches are selectable to form a patch code for conveying information about other content of a printed page containing the patch codes by accessing the data structure to obtain the respective data values;
• with a device for marking a print medium, printing a page which includes a patch code, the patch code including selected ones of the set of color patches for conveying information about the printed page;
• scanning the printed page to identify the color values for the color patches in the patch code;
• accessing the data structure to identify the data values for the identified color values of the patches in the patch code;
• and
• decoding the patch code from the identified data values to determine information about the other content of the printed page.

A calibration system for a printer comprising:

• a color patch generator for generating color patches from a set of color patches, each of the patches in the set having a unique color;
• a data structure which stores scanned color values generated by scanning a printed set of the color patches, the data structure associating, for each patch in the set, a datum value with the color values of the scanned patch, whereby, through selection of ones of the color patches, information about a calibration page is encoded;
• and
• a patch code identifier which receives color values for a scanned calibration page printed by the printer and accesses the data structure for decoding a patch code on the printed page, the patch code including patches selected from the set of color patches, the decoded patch code providing information about the scanned printed calibration page, the calibration page further comprising a target comprising color patches whose color values are used in calibrating the printer.

A computer program product comprising a tangible computer-readable recording medium encoding instructions, which when executed on a computer causes information to be encoded on a printed calibration page, the instructions comprising:

• instructions for incorporating a patch code into a calibration page to be printed, the calibration page further including a target comprising color patches to be used in calibrating a device which prints the calibration page;
• instructions for distinguishing the color patches in the patch code from the target color patches;
• instructions for accessing a data structure which stores color values and associated data values, the data values in the data structure being selectable, by selection of ones of the patch code patches, to provide information about a calibration page which is to be printed, to identify data values for color values of the patches in the patch code generated by scanning the calibration page when printed;
• and
• instructions for determining information about the printed calibration page from the identified data values of the patch code patches.