Zooming Digital Images using Interpolation Techniques

Image processing for low resolution digital images (e.g. mobile phones with low resolution camera and computed tomography (CT) scan medical images) is very challenging problems. It is because of the errors due to quantization and sampling. Over the last several years; significant improvements have been made in this area; however, it is still very challenging. In particularly, zooming of such images is very complicated. For zooming, the process of re-sampling is normally employed. Therefore, this paper focuses on investigating the effect of interpolation functions on zooming low resolution images. For this purpose, ideally, an ideal low-pass filter is preferred; however, it is difficult to realize in practice. Therefore, four interpolation functions (nearest neighbor, linear, cubic B-spline and high-resolution cubic spline with edge enhancement (-2≤a≤0)) are investigated in this paper for the low resolution medical CT scan images. From the results, it is found that cubic B-spline and high-resolution cubic spline have a better frequency response than nearest neighbor and linear interpolation functions. When these functions are applied for the purpose of zooming digital images, the best response was obtained with the high-resolution cubic spline functions; however, at the expense of increase in computation time.