Image scaling

Image scaling is the process of changing the size of a digital image. Scaling is a non-trivial process that involves a trade-off between speed, smoothness and sharpness. When increasing the size of images, the fact that digital images are made of pixels becomes particularly evident.

An image size can be changed in several ways. Consider doubling the size of following image:



The most easy way of doubling its size is to replace every pixel with four pixels of the same color.



This image shows the annoying effect that pixels of the original image are now squares: the diagonal lines of the W, for example, have now the shape of a stairway. This effect can be attenuated using other systems for changing the size of the image. For example, linear interpolation produces the following result.



Linear interpolation is typically better than the trivial system for changing the size of an image, but is not perfect. Other systems for image scaling exist.