Interpolation is a term used to describe a method to increase the size of pixels within an image. It is commonly used to increase the overall size of an image. Some digital cameras use interpolation to create digital zoom, but it is more commonly used in camera imaging software.
There are several different types of interpolation, as we'll discuss now.
- Nearest Neighbor Interpolation. This is most commonly used in-camera when reviewing and enlarging images to view details. It simply makes the pixels bigger, and the color of a new pixel is the same as the nearest original pixel. It isn't suitable for enlarging images for print as it can produce jaggies.
- Bilinear Interpolation. This takes the information from an original pixel, and four of the pixels that touch it, to decide on the color of a new pixel. It produces fairly smooth results, but it reduces the quality significantly. Images can become blurry.
- Bicubic Interpolation. This is the most sophisticated of the bunch, as it takes information from the original pixel and 16 surrounding pixels to create the color of a new pixel. Bicubic calculation is far more advanced than the other two methods, and it is capable of producing print quality images. Bicubic interpolation also offers the two variants of "Smoother" and "Sharper" for finely tuned results.
- Fractal Interpolation. Mainly used for very large prints, this samples from even more pixels than bicubic interpolation. It produces sharper edges and less blurring, but requires very specific software to run it.