Also known as continuous image, it varies continuously in a two-dimensional coordinate system. It consists of infinitely dense image points with corresponding grayscale values reflecting brightness variations.

It refers to a 2D image represented by finite numerical pixels.

Converted from analog images, digital images take pixels as basic units and can be stored and processed by computers and digital circuits.

A typical 2D digital image is equivalent to a matrix, expressed as a two-dimensional array f(x,y). Here x and y stand for coordinates in 2D space, and f(x,y) represents the grayscale and other properties at the corresponding position.