A method including streaming input image data representing an input frame of a video into temporary storage. Transformation data representing at least one transformation for application to the input image data is obtained. Ordering data indicating a variable order in which portions of output image data are to be generated is obtained, the ordering data being based on at least one characteristic of the input frame. The transformation data is used to identify portions of input image data to be processed to generate corresponding portions of output image data. The identified portions of input image data are processed to generate the corresponding portions of output image data in the order indicated by the ordering data.