An image-processing method includes: acquiring multi-level tone print data expressed in multi-level tones; determining whether the acquired multi-level tone print data includes line data indicative of a line having a tone; replacing, if the print data includes the line data, the line data with specific line data based on the tone of the line data, the specific line data indicating a specific line having a prescribed tone value and a prescribed structure; and converting the multi-level tone print data to binary data after replacing the line data with the specific line data.