1. A method of splitting a pattern to be imaged onto a substrate via a lithographic process into sub-patterns, wherein the method is implemented by a computer, the method comprising: selecting representative clips for two or more sub-patterns into which the pattern can be split, the selection being settings of the lithographic apparatus and estimated imaging quality of each of the sub-patterns; optimizing two or more optical settings for illumination from a lithographic apparatus used for the lithographic process, each optical setting being dynamically optimized for respectively imaging the two or more sub-patterns based on analysis of the representative clips; and splitting, by the computer, the pattern into the two or more sub-patterns, the sub-patterns each comprising a subset of features from the pattern, the splitting step including co-optimizing the estimated imaging quality of each of the sub-patterns for the respective optimized optical settings.