Abstract
With the development of 4K displays, fast image upsampling methods that convert the high definition contents to 4K resolution with high visual quality are critically needed. In this paper, the edge characteristics of different image areas are studied. Specific upsampling methods are used for different areas: an adaptive gradient sharpening scheme is proposed to estimate the sharper high-resolution gradient map which is utilized as a constraint to restore the sharp edges. A sharpening transformed texture image is used as another constraint to reconstruct the texture details. The two restored areas are then fused to obtain the final high-resolution (HR) image. Experimental results demonstrate that the proposed algorithm is superior or comparable to existing methods in PSNR, visual quality and especially in the running time.