An image processing device (400), comprising an image input interface (402) configured to receive input pixel values allocated to pixels in a two-dimensional pixel grid, a marker input interface (404) configured to receive marker position data indicative of a position of a marker within the pixel grid, and a marker position refining unit (406) configured to identify, using the pixel data and the marker position data, a target pixel having a highest symmetry value, i.e. identification value, which has been determined based on weighed symmetry values of the pixels within a search region that includes the marker position, and to determine a refined marker position data as the position data of the target pixel.