1. An image processing method that generates image data for controlling a liquid-ejecting recording head to form, on an image recording medium, an image made up of a plurality of dots and having resolution in a first direction and resolution in a second direction, the second direction intersecting the first direction, the resolution in the first direction being higher than the resolution in the second direction, the image processing method comprising performing contour portion correction including (a) adding image data corresponding to a dot to be formed by the liquid-ejecting recording head at a correction target pixel on the image recording medium, the correction target pixel being a pixel adjacent to a step-like contour portion in the image, and (b) when a dot is to be formed at a pixel adjacent to a pixel of interest in the first direction having the higher resolution than that in the second direction, deleting image data corresponding to the dot at the pixel of interest, the pixel of interest being adjacent to the correction target pixel in the second direction having a lower resolution than that in the first direction.