| 摘要 |
A system and related techniques generate and encode identification or transactional media such as passports, driver's licenses or others with a symbol set defined in a color space such as 8-bit color or grayscale, 24, 32, 48 or other bit depths or resolutions. Because blocks, lines or other symbol shapes may each take on more than a black or white color value, information density for the resulting bar code, biometric scan or other symbol set may be increased, and likewise take advantage of the resolution of close-contact scanners and other input devices. In embodiments, the symbols may be encoded using a selected subset of the overall color space, for instance by selecting an evenly spaced subset consisting of 4, 8 or 16 color values evenly divided within a 256 tone grayscale space, or using other values or subsets. In other embodiments the selected subset may be selected according to intervals or functions which are not evenly divided, for instance to approximate the gamma curve of a detection device, or according to other functions. The information density of the resulting IDs, credit cards, checks or other objects or media may therefore be increased, while still retaining a high degree of accuracy.
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