A method of generating an image comprising a position identifying pattern 6 and content 7 comprises the steps of: defining criteria relating to a region where the content and the pattern are superimposed, the criteria determining whether the pattern 6 will be distinguishable over the content 7 when applied to a product; identifying such a region 7 in the image; and selecting a characteristic of the pattern or the content in the region on the basis of the criteria, such that the image in the region meets the criteria.