1. A method for generating a thumbnail of an image, comprising: filtering an image to obtain an edge intensity value for each pixel point in the image; calculating a spatial position attention value of each pixel point in the image by using an attention model pre-generated according to coordinates of a center point and each pixel point of the image, as follows: P ⁡ ( i , j ) = exp ( - ( i - X c ) 2 - ( j - Y c ) 2 2 * σ 2 ) , wherein (i, j) represents a pixel point in the image; P(i, j) represents the spatial position attention value of the pixel point; (Xc, Yc) represents the center point of the image; and σ represents a preset coefficient; calculating a distribution value of information amount of each pixel point in the image by using a distribution model of information amount pre-generated according to the edge intensity values and the spatial position attention values, as follows: 
 I ( i,j )= E ( i,j )* P ( i,j ), wherein I(i, j) represents the distribution value of information amount of the pixel point; and E(i, j) represents the edge intensity value of the pixel point; sliding a preset rectangular box on the image to perform a search and, at each searched position, calculating a weight value corresponding to each pixel point in the rectangular box by using a pre-selected kernel function; multiplying the distribution value of information amount of each pixel point in the rectangular box by the corresponding weight value to obtain the weighted distribution value of information amount of each pixel point; and summarizing the weighted distribution values of information amount of all of the pixel points in the rectangular box to obtain the distribution value of information amount in the rectangular box; selecting the rectangular box with the largest distribution value of information amount; and intercepting content of the image corresponding to the selected rectangular box to obtain a thumbnail of the image.