Digital Image Processing Chapter 2 (to be continued)
1. Introduction to the basic concepts of images
Image : An image can be defined as a two-dimensional function f(x,y), where x and y are space (plane) coordinates, and the amplitude f at any pair of space coordinates (x,y) is called an image The intensity or gray scale at that point. When x, y and gray value f are finite discrete values, we call the image a digital image.
Gray level number : For storage and quantization hardware considerations, the gray level number is usually an integer power of 2, that is, L=2 k and they are integers in the interval [0, L-1].
Dynamic range : The ratio of the maximum measurable gray scale to the minimum detectable gray scale in the system.
Contrast : The gray difference between the highest and lowest gray levels in an image is defined as the
four-neighbors of contrast : the pixel P located at coordinates (x, y) has 4 horizontal and vertical adjacent pixels, and its coordinates are ( x+1,y), (x-1,y), (x,y+1), (x,y-1), this group of pixels is called the four-neighborhood of P, denoted by N 4(P ).
Eight-neighborhood : The coordinates of the 4 diagonal adjacent pixels of P are (x+1,y+1), (x-1,y-1), (x-1,y+1), (x+1 ,y-1), represented by N D(P). And N D(P) and N 4(P) together are called the eight neighborhood of P, denoted by N 8(P ).
2. Contiguity
Let V be the set of gray values used to define adjacency. In a binary image, if a pixel with a value of 1 is classified as an adjacent pixel, then V={1}.
(A) , 4 is adjacent. If q is in the set N 4(P), then two pixels p and q with values in V are 4 adjacent.
(B)、8 adjacent. If q is in the set N 8(P), then the two well-known pixels p and q in V are 8 adjacent.
(C) , m adjacent (mixed adjacent). If q is in N 4(P ), or q is in N D(P ), and there is no pixel from the value in V in the set N 4(P) ∩ N 4(q ), then two pixels p and q with the value in V It is adjacent to m.