Method of superimposing an image onto another, method of personalizing a data carrier using the image superimposing method and a personalized data carrier

A software program executable by a computing device for superimposing a first image onto a second image, wherein each image is defined by a plurality of pixels, the software program including instructions for executing steps comprising:

• changing target pixels of the second image corresponding in position to pixels of the first image to be superimposed on the second image,
• wherein changing target pixels of the second image comprises changing the value of each of these target pixels of the second image to a new value that is based on the original value of at least one pixel of the second image.

A data carrier comprising:

• an identification image and a security pattern image printed thereat, the images at least partially overlapping each other;
• wherein the security pattern image is defined by a plurality of pixels, each of at least some of whose appearances bear a tonal or colour relationship to its respective at least one neighbouring pixel of the identification image.