A first derived matrix of transport coefficients and a second derived matrix of transport coefficients are derived from a primary matrix of transport coefficients. Each of the transport coefficients describes transport of a respective image forming element from a first position onto one or more image forming elements at a second position. An approximate inverse of the first derived matrix is ascertained. A modified version of a projection image is determined from the projection image, the approximated inverse of the first derived matrix, and the second derived matrix. The modified version of the projection image is rendered from the first position onto a physical medium at the second position.