A Method of Bicubic Image Interpolation with Direction Parameter

Traditional bicubic interpolation only interpolates missing pixels in horizontal or vertical directions and incurs blurring, ringing artifacts along edges or textures easily. Aiming at this problem, a method of bicubic image interpolation with direction parameter is proposed. This method detects local directions and strengths by means of computing gradients along horizontal, vertical, 45°and 135° in the first. If pixels are on strong edges, 1D bicubic interpolation with corresponding direction is used directly. Otherwise, first interpolate along two directions with the biggest gradients respectively and then combine them with appropriate weights. Besides, in order to decrease computational complexity, bilinear interpolation is used dramatically based on local variance in this paper. Compared with bicubic method, the proposed method preserves sharp edges and details better and can accommodate arbitrary scaling factors as well. Experiments show that the proposed method is better than modern edge-directed interpolations in terms of subjective (such as PSNR) and objective (such as SSIM) measures, and the computational complexity is also relatively low.