Color Image Zooming

Definition: Image zooming or spatial interpolation of a digital image is the process of increasing the number of pixels representing the natural scene.

Image zooming is frequently used in high resolution display devices and consumer-grade digital cameras . Unlike spectral interpolation, spatial interpolation preserves the spectral representation of the input. Operating on the spatial domain of a digital image, spatial interpolation transforms a gray-scale or color image into an enlarged gray-scale or color image (Figure 1), respectively.

In the single-sensor imaging pipeline, color image zooming operates on the recorded demosaicked image. Such a pipeline typically employs a demosaicking scheme at the first processing stage to produce a full color image. The spatial resolution of the demosaicked image is then increased using a color image zooming technique operating on the RGB color vectors (Figure 2).

It should be noted that since natural color images exhibit strong spectral correlation, traditional image zooming methods, which separately process each color channel, often introduce color artifacts. To alleviate the problem and preserve the spectral correlation of the enlarged image’s color channels, vector processing is recommended. Vector techniques process the available color pixels as set of vectors and are able to reduce the presence of most color artifacts and eliminate shifted color edges.