Method and apparatus for decoding angular orientation of lattice codes

An angular orientation of a lattice image pattern is found by forming a composite image of superimposed portions of a lattice image by aligning centroids of a lattice element in each portion, and determining a lattice axis from a line fit through centroids of lattice elements in the composite image. The composite image is formed by selecting a seed pixel, finding a local minimum near the seed pixel and then finding a centroid based on the local minimum. From the centroid, it is determined whether the glyph centroid has sufficient contrast to be included in the composite image. The composite image is formed by superimposing subsamples of the lattice image based on glyph centroids. The composite image is then analyzed to determine a lattice axis through centroids in the composite image, and determining a quadrant image based on the lattice axis.