1. A method for generating a projection image from tomographic images, the method comprising the following steps: capturing a plurality of stacked two-dimensional tomographic images representing a tomographic volume; weighting pixels of the stacked two-dimensional tomographic images along a number of projection beams through the tomographic volume with weighting factors chosen under a constraint that a sum of all squared weighting factors for each individual projection beam lies between a given lower limit and a given upper limit, the given lower limit set equal to the given upper limit; and generating the two-dimensional projection image by summing up the weighted pixels along the number of projection beams.