Image Up/Down Scaler

Scalers have a variety of applications in image and video broadcasting systems where users are allowed to vary the resolutions of images interactively in order to concentrate on some details or to get a better overview. When a video sequence is displayed on an LCD or PDP monitor for digital TV, which can have a resolution varying from QCIF to ultra- high definition (UHD), the original data have to be resampled by interpolation according to the resolution supported by the display devices.

The following figures show that the shape of the kernel depends on tuning parameter . When alpha is a negative number having a large amplitude, the kernel consists of a narrow center part and rapidly changing ends. On the other hand, a positive alpha smooths the shape of the kernel. 

The optimization algorithm for alpha to increase the quality of the scaled image is explained as follows.

To provide a qualitative evaluation of the proposed method, the results of the conventional schemes and proposed method for an enlargement test (with a scaling ratio of 3.8) are compared in the following pictures. As shown in these figures, the BK and PCC perform better with respect to the subjective image quality than the other methods. The performance of PCC is almost the same as that of BK.