A vector-based approach to digital image scaling

Image and video capture devices are often designed with different capabilities and end-users in mind. As a result, very often images are captured at one resolution and need to be displayed at another resolution. Resizing thus continues to be an important research area in today's milieu. Well-known pixel-based methods (like bicubic interpolation) have traditionally been used for the purpose. However, these methods are often found lacking in quality from a perceptual standpoint as they tend to soften edges and blur details. Recently, vectorization based approaches have been explored because of their inherent property of artifact free scaling. However, these methods fail to faithfully reproduce textures and fine details in an image. In this work, we present a novel, layered approach of combining image vectorization with a pixel based interpolation technique to achieve high quality scaling of digital images. The proposed method decomposes an image into two layers: a `coarse' layer capturing the visually important structure of the image, and a `fine' layer containing the details. We vectorize only the coarse layer and render at the desired scale, while using classical interpolation on the fine layer. The final scaled image is composed by blending the independently scaled layers. We compare the performance of the proposed method with several state-of-the-art vectorization and scaling methods, and report comparably better performance.