A method processes image data in a color separation to attenuate printing defects arising from misalignment of serially arranged printheads that eject ink for the color separation. The method includes processing image values of the color separation with a first rendering process that corresponds to one printhead in a plurality of serially arranged printheads for printing the color separation, processing the image values of the color separation with a second rendering process that differs from the first rendering process for at least one other printhead in the plurality of serially arranged printheads for printing the color separation, generating firing signals for the one printhead from the rendered image values generated by the first rendering process, and generating firing signals for the at least one other printhead from the rendered image values generated by the second rendering process.