1. A method of superimposing a first image onto a second image for creating a target image, wherein the first image, the second image, and the target image each are defined by a plurality of pixels, each pixel being associated with a pixel value, the method comprising: changing a pixel value of the target image to be equal to a pixel value of the second image if the corresponding pixel value of the first image is equal to zero; changing the pixel value of the target image to be equal to the pixel value of the first image if the corresponding pixel value of the first image is not equal to zero, wherein for each pixel of the target image corresponding to a pixel of the first image, a contrast evaluation is performed between the corresponding pixel of the first image and a neighboring pixel of the second image, and the pixel value of the target image is increased or decreased based on the evaluation result in order to obtain a visible contrast between the first and second image in all parts of the target image.