Importance

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Abstract

A self-clocking glyph code is provided for encoding dual bit digital values in the cardinal rotations (0.degree., 90.degree., 180.degree. and 270.degree.) of a logically ordered sequence of wedge-shaped glyphs that are written, printed, or otherwise recorded on a hardcopy recording medium in accordance with a predetermined spatial formatting rule. For example, these wedge-shaped glyphs suitably are essentially identical right triangles. The widths of such glyphs vary unidirectionally as a function of their height, so they can be decoded reliably, even when they are degraded by scan errors, dropped scan lines and/or random noise patterns. The decoding can be carried out in a variety of different ways, including by means of a bounding box analysis of the glyphs to determine whether the center of mass of each glyph is in the upper right, upper left, lower right or lower left quadrant of its bounding box; or by means of a bounding box analysis of the glyphs to determine whether the inclined surface of each wedge is on its right-hand side or its left-hand side and tilted to the right or left; or by means of a comparative run length analysis of each of the glyphs to determine whether its shortest run of adjacent ON pixels is spatially located above or below, and to the right or left of center of, its longest run of adjacent ON pixels.

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First Claim