1. A method in an image decoder for assigning pixel values to pixels in a prediction region of an image, the method comprising: obtaining a reference vector provided by the image encoder, determining an initiation region of pixels corresponding to a reference region of pixels at the image encoder, the initiation region being spatially displaced in relation to the prediction region according to the reference vector and partly overlapping with the prediction region, wherein pixel values of pixels in overlapping parts of the initiation and prediction regions are unknown, assigning pixel values to the pixels in the overlapping parts of the initiation and prediction regions by assigning known pixel values of pixels in a non-overlapping part of the initiation region to pixels in a corresponding part of the prediction region, wherein the pixels in the corresponding part of the prediction region at least include the pixels in the overlapping parts of the initiation and prediction regions, and assigning the pixel values assigned to the pixels in the overlapping part of the initiation region to the corresponding pixels in the prediction region.