1. A method for converting monochrome images comprising steps of: blocking a monochrome image; obtaining pixel values of monochrome image blocks; layered mapping of the monochrome image with equal grayscale to obtain color values of equal grayscale layers for the monochrome image; assigning each of the equal grayscale layers a corresponding color; and matching the monochrome image blocks with colors corresponding to the equal grayscale layers according to the color values and the pixel values.