A digital image (40) comprises pixels with intensities relating to different energy levels. A method for processing the digital image (40) comprises the steps of: receiving first image data (42a) and second image data (42b) of the digital image (40), the first image data (42a) encoding a first energy level and the second image data (42b) encoding a second energy level; determining a regression model (44) from the first image data (42a) and the second image data (42b), the regression model (44) establishing a correlation between intensities of pixels of the first image data (42a) with intensities of pixels of the second image data (42b); and calculating residual mode image data (46) from the first image data (42a) and the second image data (42b), such that a pixel of the residual mode image data (46) has an intensity based on the difference of an intensity of the second image data (42b) at the pixel and a correlated intensity of the pixel of the first image data (42a), the correlated intensity determinate by applying the regression model to the intensity of pixel of the first image data (42a).