Efficient Downscaling of JPEG-Compressed Images

We introduce an efficient downscaling methods with arbitrary downscaling factors for images that are transformed to DCT blocks as in the compression standard JPEG. Our hybrid approach combines the low complexity of DCT domain downscaling with the high image quality of B-spline based downscaling methods. A scalable parameter allows to adjust the trade-off between computational costs and image quality. Results from numerical experiments demonstrate the superiority of the new method in terms of efficiency compared to the existing methods. Furthermore, our method results in a scalable trade-off between the image quality and the computational costs.