1. An image encoding method based on a region of interest (ROI), the image encoding comprising: determining an ROI to be duplicated in an image to be encoded; estimating image features of blocks located in the ROI; defining duplication magnifications of the respective blocks located in the ROI using the estimated image features; transforming the image by duplicating the blocks located in the ROI in a specific direction according to the defined duplication magnifications; and encoding the transformed image.