In this paper, we propose a novel image interpolation technique using the small-kernel bilateral filter. The range distance of the bilateral filter is estimated using a novel maximum a posterior (MAP) estimation, in order to consider both the diagonal and vertical-horizontal correlations in image. The proposed method requires a few arithmetic operations, such that it is suitable for real time image zoom, video up-scaling and video transcoding applications in HDTV systems. Subjective evaluation shows that the proposed approach outperforms the conventional method in terms of edge sharpness and edge smoothness.