We have previously described the printing of information in 2D color (or "3D") barcodes for subsequent reading with scanners and/or mobile cameras. In this paper, we describe how color tiles can be used in different aggregations (single tiles, 2x2 pairings of tiles, 3x3 pairings of tiles, etc.) to provide data that is readable by a wide array of imaging devices. High-end devices such as scanners and line cameras will accurately read each individual (small) module, or tile, in the barcode, while less expensive cameras, such as cameras in mobile phones, will only be able to accurately read clusters of the tiles (e.g. 2x2 module "aggregations") at a time. We address this by using a novel type of error-correcting code, the CET (chroma-enhancing tile), which reduces the payload density by 25% for a 2x2 pairing, but allows 2x2 pairings to reliably map to the same set of colors - usually {RGBCMY} - as the original (single) modules. This makes the color barcodes readable to to a wide array of imaging devices. In addition, we describe in this paper how the use of three or more colors-optimally the six colors {RGBCMY}.enables a "dual-channel" authentication approach, with a second novel type of error-correcting code-the color- multiplicity-to-color-axis mapping (CMCAM)-enabling a different interpretation of the colors in the barcodes to suit the color capabilities of the imaging device. Our data show that, in some cases, authentication with a CMCAM-reduced palette can actually increase payload density for some imaging devices.
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