1. A method of decoding a machine-readable symbol configured as a set of marks formed in a surface of an object, a presence or absence of a mark in each cell of an array of cells designating a binary state of the each cell, the method comprising: acquiring an image of the machine-readable symbol; identifying the cells of the array from the acquired image; evaluating reference cells of the array in accordance with a reference standard for the machine-readable symbol to identify optical characteristics consistent with the presence or absence of a mark in the reference cells; classifying nonreference cells of the array in accordance with the identified optical characteristics to determine the presence or absence of a mark in the nonreference cells; compiling classifications of the nonreference cells into a binary grid; and decoding the binary grid, wherein: acquiring the image of the machine-readable symbol comprises illuminating the machine-readable symbol with a plurality of illumination sources having different illumination spectra; and evaluating reference cells of the array and classifying nonreference cells of the array comprises separating chromatic components of the acquired image.