Image filter values can be obtained by applying a high-frequency or edge-detection image filter to an image to extract a level of image detail. The image can be divided into blocks of a predetermined size and the image filter values of the pixels in a block can be used to obtain a density value associated with the level of image detail for the block. For blocks where the density value exceeds a threshold amount, a degree of blur may be applied based on the density value. Thus, the image can be rendered so that only some of the blocks of the image are blurred while other blocks do not have blur applied.