The original image serves as input to a computational process that acts as a filter. Like the filters of conventional photography, the result is a transformed image. But in digital filtering, a second output image is produced. Beacuse the output image is created by performing mathematical operations on pixels from the original or input image, digital filtering has several distinct advantages over conventional methods. The process is more precise and, therefore, can be more easily controlled.
Precision also means that it is easily repeatable.
For example, we may perform the same process reliably with an assortment of images. Finally, since input and output images are distinct, we may also experiment with their effects without sacrificing the integrity of the original image. There are two classes of digital filtering. Global filtering refers to operations that are performed on the entire image as a whole. In other words, each pixel is uniformly treated by the digital filter.