Method and apparatus for reading a surface coded pattern
AssigneeHewlett-Packard Development Company, L.P.
InventorsMaurizio Pilu, Guy Adams
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Abstract
A method of determining a regular grid pattern from a surface coded pattern that comprises the regular grid pattern interleaved with a further data carrying pattern wherein the surface coded pattern is subject to perspective distortion, the method comprising: extracting a set of straight line hypotheses from the coded surface pattern; clustering the straight line hypotheses by orientation; for each cluster, extracting a set of line pencil hypotheses; generating a set of regular grid hypotheses from pairs of the line pencil hypotheses; and determining the best regular grid hypothesis.
Claims19
A method of determining a regular grid pattern from a surface coded pattern that comprises the regular grid pattern interleaved with a further data carrying pattern wherein the surface coded pattern is subject to perspective distortion, the method comprising:
- extracting a set of straight line hypotheses from the surface coded pattern by identifying a plurality of surface pattern points that are co-linear to one another, identifying sets of the plurality of surface pattern points that are co-linear to one another, deleting sets of the plurality of surface pattern points that have a cross-ratio value outside a predetermined range, and fitting a line hypothesis to sets of the plurality of surface pattern points that have a cross-ratio value within the predetermined range;
- clustering the straight line hypotheses by orientation;
- for each cluster, extracting a set of line pencil hypotheses;
- generating a set of regular grid hypotheses from pairs of the line pencil hypotheses;
- and
- determining, by a processor, a regular grid hypothesis closest to a true regular grid.
A non-transitory computer readable medium having stored thereon machine readable instructions for determining a regular grid pattern from a surface coded pattern that comprises the regular grid pattern interleaved with a further data carrying pattern wherein the surface coded pattern is subject to perspective distortion, the machine readable instructions when executed cause a computer system to:
- extract a set of straight line hypotheses from the surface coded pattern;
- cluster the straight line hypotheses by orientation by grouping the straight line hypotheses into a plurality of sets encompassing straight line hypotheses with an angular orientation about a center of the surface coded pattern within a predetermined range;
- for each cluster, extract a set of line pencil hypotheses;
- generate a set of regular grid hypotheses from pairs of the line pencil hypotheses;
- and
- determine, by a processor, a regular grid hypothesis closest to a true regular grid.
Apparatus for determining a regular grid pattern from a surface coded pattern that comprises the regular grid pattern interleaved with a further data carrying pattern wherein the surface coded pattern is subject to perspective distortion, the apparatus comprising:
- an imaging system arranged to capture an electronic image of the ceded surface coded pattern;
- and
- a data processor arranged to execute machine readable instructions to:
- extract a set of straight line hypotheses from the surface coded pattern by identifying a plurality of surface pattern points that are co-linear to one another, identifying sets of the plurality of surface pattern points that are co-linear to one another, deleting sets of the plurality of surface pattern points that have a cross-ratio value outside a predetermined range, and fitting a line hypothesis to sets of the plurality of surface pattern points that have a cross-ratio value within the predetermined range;
- cluster the straight line hypotheses by orientation;
- for each cluster, extract a set of line pencil hypotheses;
- generate a set of regular grid hypotheses from pairs of the line pencil hypotheses;
- and
- determine a regular grid hypothesis closest to a true regular grid.
Dependencies are inferred from the claim text.