METHOD AND APPARATUS FOR ANALYZING AND CONVERTING BI-LEVEL IMAGE DATA

A bi-level image, coded as transition data indicating positions of transitions in individual dot lines, is analyzed by comparing transition positions occurring in a consecutive group of dot lines, and detecting segments in different dot lines in the group that have the same level and join up in the direction parallel to the dot lines. The line density of the bi-level image can be reduced by replacing the group of dot lines with a single new dot line that includes the transition positions of all dot lines in the group, except for interior transition positions of joining segments. The line density can be increased by copying transition data of each dot line to a new dot line, adjusting the transition positions of segments that join segments in an adjacent dot line.