  A novel algorithm, called semantic line combination detector (SLCD), to find
an optimal combination of semantic lines is proposed in this paper. It
processes all lines in each line combination at once to assess the overall
harmony of the lines. First, we generate various line combinations from
reliable lines. Second, we estimate the score of each line combination and
determine the best one. Experimental results demonstrate that the proposed SLCD
outperforms existing semantic line detectors on various datasets. Moreover, it
is shown that SLCD can be applied effectively to three vision tasks of
vanishing point detection, symmetry axis detection, and composition-based image
retrieval. Our codes are available at https://github.com/Jinwon-Ko/SLCD.
