1. An image processing method that generates image data of 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 different from the resolution in the second direction, the image processing method comprising performing contour portion correction including adding a dot at a correction target pixel, the correction target pixel being a pixel adjacent to a step-like contour portion in the image, and when a dot is arranged at a pixel adjacent to a pixel of interest adjacent to the correction target pixel, deleting the dot at the pixel of interest.