A vector data processor (12) includes a thinning part (301), a central line acquiring part (302), and a superimposing part (303). A target figure includes a linear figure. The thinning part (301) processes target vector data (231) to acquire thinned data (232) by thinning the target figure indicated by the target vector data (231). The central line acquiring part (302) processes the target vector data (231) to acquire central line data (233) that indicates a central line of the target figure. The superimposing part (303) generates data that includes an instruction to record a combined figure obtained by superimposing the thinned figure and the central line one above the other. Superimposing the thinned figure and the central line enables the target figure to be thinned without line becoming broken. The shape of a rasterized figure can be approximated to the shape of a figure indicated by original data.
