An image is displayed in a computer system. The image includes contents having a feature visible therein. The contents have a region thereof defined to be provided with additional content in generating a modified image. An input is received comprising a semantic mark to be placed on the image. The semantic mark indicates an inside-region part inside the region and an outside-region part outside the region. The additional content for the region is determined using a patch-based optimization algorithm applied to the image. The patch-based optimization algorithm (i) identifies the additional content for the inside-region part based on the outside-region part and not on an area of the image that the semantic mark does not indicate, and (ii) identifies the additional content for a remainder of the region without being restricted to the outside-region part. The modified image having the additional content in the region is stored.